|amphetamine aspartate monohydrate||25% – stimulant|
(12.5% levo; 12.5% dextro)
|amphetamine sulfate||25% – stimulant|
(12.5% levo; 12.5% dextro)
|dextroamphetamine saccharate||25% – stimulant|
(0% levo; 25% dextro)
|dextroamphetamine sulfate||25% – stimulant|
(0% levo; 25% dextro)
|Trade names||Adderall, Adderall XR, Mydayis|
|Oral, insufflation, rectal, sublingual|
Adderall[note 1] is a combination medication containing four salts of amphetamine. Adderall is used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It is also used as an athletic performance enhancer and cognitive enhancer, and recreationally as an aphrodisiac and euphoriant. It is a central nervous system (CNS) stimulant of the phenethylamine class. By salt content, the active ingredients are 25% levoamphetamine salts (the levorotatory or 'left-handed' enantiomer) and 75% dextroamphetamine salts (the dextrorotatory or 'right-handed' enantiomer).[note 2][sources 1]
Adderall is generally well-tolerated and effective in treating the symptoms of ADHD and narcolepsy. At therapeutic doses, Adderall causes emotional and cognitive effects such as euphoria, change in desire for sex, increased wakefulness, and improved cognitive control. At these doses, it induces physical effects such as a faster reaction time, fatigue resistance, and increased muscle strength. In contrast, much larger doses of Adderall can impair cognitive control, cause rapid muscle breakdown, or induce a psychosis (e.g., delusions and paranoia). The side effects of Adderall vary widely among individuals, but most commonly include insomnia, dry mouth, and loss of appetite. The risk of developing an addiction is insignificant when Adderall is used as prescribed at fairly low daily doses, such as those used for treating ADHD; however, the routine use of Adderall in larger daily doses poses a significant risk of addiction due to the pronounced reinforcing effects that are present at high doses. Recreational doses of Adderall are generally much larger than prescribed therapeutic doses, and carry a far greater risk of serious adverse effects.[sources 2]
The two amphetamine enantiomers that compose Adderall (i.e., levoamphetamine and dextroamphetamine) alleviate the symptoms of ADHD and narcolepsy by increasing the activity of the neurotransmitters norepinephrine and dopamine in the brain, which results in part from their interactions with human trace amine-associated receptor 1 (hTAAR1) and vesicular monoamine transporter 2 (VMAT2) in neurons. Dextroamphetamine is a more potent CNS stimulant than levoamphetamine, but levoamphetamine has slightly stronger cardiovascular and peripheral effects and a longer elimination half-life (i.e., it remains in the body longer) than dextroamphetamine. The levoamphetamine component of Adderall has been reported to improve the treatment response in some individuals relative to dextroamphetamine alone. Adderall's active ingredient, amphetamine, shares many chemical and pharmacological properties with the human trace amines, particularly phenethylamine and N-methylphenethylamine, the latter of which is a positional isomer of amphetamine.[sources 3] In 2016, it was the 45th most prescribed medication in the United States, with more than 17 million prescriptions.
Adderall is used to treat attention deficit hyperactivity disorder (ADHD) and narcolepsy (a sleep disorder). Long-term amphetamine exposure at sufficiently high doses in some animal species is known to produce abnormal dopamine system development or nerve damage, but, in humans with ADHD, pharmaceutical amphetamines appear to improve brain development and nerve growth. Reviews of magnetic resonance imaging (MRI) studies suggest that long-term treatment with amphetamine decreases abnormalities in brain structure and function found in subjects with ADHD, and improves function in several parts of the brain, such as the right caudate nucleus of the basal ganglia.
Reviews of clinical stimulant research have established the safety and effectiveness of long-term continuous amphetamine use for the treatment of ADHD. Randomized controlled trials of continuous stimulant therapy for the treatment of ADHD spanning 2 years have demonstrated treatment effectiveness and safety. Two reviews have indicated that long-term continuous stimulant therapy for ADHD is effective for reducing the core symptoms of ADHD (i.e., hyperactivity, inattention, and impulsivity), enhancing quality of life and academic achievement, and producing improvements in a large number of functional outcomes[note 3] across 9 categories of outcomes related to academics, antisocial behavior, driving, non-medicinal drug use, obesity, occupation, self-esteem, service use (i.e., academic, occupational, health, financial, and legal services), and social function. One review highlighted a nine-month randomized controlled trial of amphetamine treatment for ADHD in children that found an average increase of 4.5 IQ points, continued increases in attention, and continued decreases in disruptive behaviors and hyperactivity. Another review indicated that, based upon the longest follow-up studies conducted to date, lifetime stimulant therapy that begins during childhood is continuously effective for controlling ADHD symptoms and reduces the risk of developing a substance use disorder as an adult.
Current models of ADHD suggest that it is associated with functional impairments in some of the brain's neurotransmitter systems; these functional impairments involve impaired dopamine neurotransmission in the mesocorticolimbic projection and norepinephrine neurotransmission in the noradrenergic projections from the locus coeruleus to the prefrontal cortex. Psychostimulants like methylphenidate and amphetamine are effective in treating ADHD because they increase neurotransmitter activity in these systems. Approximately 80% of those who use these stimulants see improvements in ADHD symptoms. Children with ADHD who use stimulant medications generally have better relationships with peers and family members, perform better in school, are less distractible and impulsive, and have longer attention spans. The Cochrane reviews[note 4] on the treatment of ADHD in children, adolescents, and adults with pharmaceutical amphetamines stated that short-term studies have demonstrated that these drugs decrease the severity of symptoms, but they have higher discontinuation rates than non-stimulant medications due to their adverse side effects. A Cochrane review on the treatment of ADHD in children with tic disorders such as Tourette syndrome indicated that stimulants in general do not make tics worse, but high doses of dextroamphetamine could exacerbate tics in some individuals.
Adderall is available as immediate-release tablets or two different extended-release formulations. The extended-release capsules are generally used in the morning. A shorter, 12-hour extended-release formulation is available under the brand Adderall XR and is designed to provide a therapeutic effect and plasma concentrations identical to taking two doses 4 hours apart. The longer extended-release formulation, approved for 16 hours, is available under the brand Mydayis. In the United States, the immediate and extended release (XR) formulations of Adderall are both available as generic drugs, while Mydayis is available only as a brand-name drug.
In 2015, a systematic review and a meta-analysis of high quality clinical trials found that, when used at low (therapeutic) doses, amphetamine produces modest yet unambiguous improvements in cognition, including working memory, long-term episodic memory, inhibitory control, and some aspects of attention, in normal healthy adults; these cognition-enhancing effects of amphetamine are known to be partially mediated through the indirect activation of both dopamine receptor D1 and adrenoceptor α2 in the prefrontal cortex. A systematic review from 2014 found that low doses of amphetamine also improve memory consolidation, in turn leading to improved recall of information. Therapeutic doses of amphetamine also enhance cortical network efficiency, an effect which mediates improvements in working memory in all individuals. Amphetamine and other ADHD stimulants also improve task saliency (motivation to perform a task) and increase arousal (wakefulness), in turn promoting goal-directed behavior. Stimulants such as amphetamine can improve performance on difficult and boring tasks and are used by some students as a study and test-taking aid. Based upon studies of self-reported illicit stimulant use, 5–35% of college students use diverted ADHD stimulants, which are primarily used for enhancement of academic performance rather than as recreational drugs. However, high amphetamine doses that are above the therapeutic range can interfere with working memory and other aspects of cognitive control.
Adderall has been banned in the National Football League (NFL), Major League Baseball (MLB), National Basketball Association (NBA), and the National Collegiate Athletics Association (NCAA). In leagues such as the NFL, there is a very rigorous process required to obtain an exemption to this rule even when the athlete has been medically prescribed the drug by their physician.
Adderall has high potential for misuse as a recreational drug. Adderall tablets can be crushed and snorted, or dissolved in water and injected. Injection into the bloodstream can be dangerous because insoluble fillers within the tablets can block small blood vessels.
Many postsecondary students have reported using Adderall for study purposes in different parts of the developed world. Among these students, some of the risk factors for misusing ADHD stimulants recreationally include: possessing deviant personality characteristics (i.e., exhibiting delinquent or deviant behavior), inadequate accommodation of special needs, basing one's self-worth on external validation, low self-efficacy, earning poor grades, and suffering from an untreated mental health disorder.
The adverse side effects of Adderall are many and varied, but the amount of substance consumed is the primary factor in determining the likelihood and severity of side effects. Adderall is currently approved for long-term therapeutic use by the USFDA. Recreational use of Adderall generally involves far larger doses and is therefore significantly more dangerous, involving a much greater risk of serious adverse drug effects than dosages used for therapeutic purposes.
At normal therapeutic doses, the physical side effects of amphetamine vary widely by age and from person to person. Cardiovascular side effects can include hypertension or hypotension from a vasovagal response, Raynaud's phenomenon (reduced blood flow to the hands and feet), and tachycardia (increased heart rate). Sexual side effects in males may include erectile dysfunction, frequent erections, or prolonged erections. Gastrointestinal side effects may include abdominal pain, constipation, diarrhea, and nausea. Other potential physical side effects include appetite loss, blurred vision, dry mouth, excessive grinding of the teeth, nosebleed, profuse sweating, rhinitis medicamentosa (drug-induced nasal congestion), reduced seizure threshold, tics (a type of movement disorder), and weight loss.[sources 4] Dangerous physical side effects are rare at typical pharmaceutical doses.
Amphetamine stimulates the medullary respiratory centers, producing faster and deeper breaths. In a normal person at therapeutic doses, this effect is usually not noticeable, but when respiration is already compromised, it may be evident. Amphetamine also induces contraction in the urinary bladder sphincter, the muscle which controls urination, which can result in difficulty urinating. This effect can be useful in treating bed wetting and loss of bladder control. The effects of amphetamine on the gastrointestinal tract are unpredictable. If intestinal activity is high, amphetamine may reduce gastrointestinal motility (the rate at which content moves through the digestive system); however, amphetamine may increase motility when the smooth muscle of the tract is relaxed. Amphetamine also has a slight analgesic effect and can enhance the pain relieving effects of opioids.
USFDA-commissioned studies from 2011 indicate that in children, young adults, and adults there is no association between serious adverse cardiovascular events (sudden death, heart attack, and stroke) and the medical use of amphetamine or other ADHD stimulants.[sources 5] However, amphetamine pharmaceuticals are contraindicated in individuals with cardiovascular disease.[sources 6]
At normal therapeutic doses, the most common psychological side effects of amphetamine include increased alertness, apprehension, concentration, initiative, self-confidence and sociability, mood swings (elated mood followed by mildly depressed mood), insomnia or wakefulness, and decreased sense of fatigue. Less common side effects include anxiety, change in libido, grandiosity, irritability, repetitive or obsessive behaviors, and restlessness;[sources 7] these effects depend on the user's personality and current mental state. Amphetamine psychosis (e.g., delusions and paranoia) can occur in heavy users. Although very rare, this psychosis can also occur at therapeutic doses during long-term therapy. According to the USFDA, "there is no systematic evidence" that stimulants produce aggressive behavior or hostility.
Amphetamine has also been shown to produce a conditioned place preference in humans taking therapeutic doses, meaning that individuals acquire a preference for spending time in places where they have previously used amphetamine.
|Addiction and dependence glossary|
Addiction is a serious risk with heavy recreational amphetamine use, but is unlikely to occur from long-term medical use at therapeutic doses; in fact, lifetime stimulant therapy for ADHD that begins during childhood reduces the risk of developing substance use disorders as an adult. Pathological overactivation of the mesolimbic pathway, a dopamine pathway that connects the ventral tegmental area to the nucleus accumbens, plays a central role in amphetamine addiction. Individuals who frequently self-administer high doses of amphetamine have a high risk of developing an amphetamine addiction, since chronic use at high doses gradually increase the level of accumbal ΔFosB, a "molecular switch" and "master control protein" for addiction. Once nucleus accumbens ΔFosB is sufficiently overexpressed, it begins to increase the severity of addictive behavior (i.e., compulsive drug-seeking) with further increases in its expression. While there are currently no effective drugs for treating amphetamine addiction, regularly engaging in sustained aerobic exercise appears to reduce the risk of developing such an addiction. Sustained aerobic exercise on a regular basis also appears to be an effective treatment for amphetamine addiction;[sources 8] exercise therapy improves clinical treatment outcomes and may be used as a combination therapy with cognitive behavioral therapy, which is currently the best clinical treatment available.
Chronic use of amphetamine at excessive doses causes alterations in gene expression in the mesocorticolimbic projection, which arise through transcriptional and epigenetic mechanisms. The most important transcription factors[note 8] that produce these alterations are Delta FBJ murine osteosarcoma viral oncogene homolog B (ΔFosB), cAMP response element binding protein (CREB), and nuclear factor-kappa B (NF-κB). ΔFosB is the most significant biomolecular mechanism in addiction because ΔFosB overexpression (i.e., an abnormally high level of gene expression which produces a pronounced gene-related phenotype) in the D1-type medium spiny neurons in the nucleus accumbens is necessary and sufficient[note 9] for many of the neural adaptations and regulates multiple behavioral effects (e.g., reward sensitization and escalating drug self-administration) involved in addiction. Once ΔFosB is sufficiently overexpressed, it induces an addictive state that becomes increasingly more severe with further increases in ΔFosB expression. It has been implicated in addictions to alcohol, cannabinoids, cocaine, methylphenidate, nicotine, opioids, phencyclidine, propofol, and substituted amphetamines, among others.[sources 9]
ΔJunD, a transcription factor, and G9a, a histone methyltransferase enzyme, both oppose the function of ΔFosB and inhibit increases in its expression. Sufficiently overexpressing ΔJunD in the nucleus accumbens with viral vectors can completely block many of the neural and behavioral alterations seen in chronic drug abuse (i.e., the alterations mediated by ΔFosB). ΔFosB also plays an important role in regulating behavioral responses to natural rewards, such as palatable food, sex, and exercise. Since both natural rewards and addictive drugs induce the expression of ΔFosB (i.e., they cause the brain to produce more of it), chronic acquisition of these rewards can result in a similar pathological state of addiction. Consequently, ΔFosB is the most significant factor involved in both amphetamine addiction and amphetamine-induced sexual addictions, which are compulsive sexual behaviors that result from excessive sexual activity and amphetamine use. These sexual addictions are associated with a dopamine dysregulation syndrome which occurs in some patients taking dopaminergic drugs.
The effects of amphetamine on gene regulation are both dose- and route-dependent. Most of the research on gene regulation and addiction is based upon animal studies with intravenous amphetamine administration at very high doses. The few studies that have used equivalent (weight-adjusted) human therapeutic doses and oral administration show that these changes, if they occur, are relatively minor. This suggests that medical use of amphetamine does not significantly affect gene regulation.
As of 2015,[update] there is no effective pharmacotherapy for amphetamine addiction. Reviews from 2015 and 2016 indicated that TAAR1-selective agonists have significant therapeutic potential as a treatment for psychostimulant addictions; however, as of February 2016,[update] the only compounds which are known to function as TAAR1-selective agonists are experimental drugs. Amphetamine addiction is largely mediated through increased activation of dopamine receptors and co-localized NMDA receptors[note 10] in the nucleus accumbens; magnesium ions inhibit NMDA receptors by blocking the receptor calcium channel. One review suggested that, based upon animal testing, pathological (addiction-inducing) psychostimulant use significantly reduces the level of intracellular magnesium throughout the brain. Supplemental magnesium[note 11] treatment has been shown to reduce amphetamine self-administration (i.e., doses given to oneself) in humans, but it is not an effective monotherapy for amphetamine addiction.
Cognitive behavioral therapy is currently the most effective clinical treatment for psychostimulant addictions. Additionally, research on the neurobiological effects of physical exercise suggests that daily aerobic exercise, especially endurance exercise (e.g., marathon running), prevents the development of drug addiction and is an effective adjunct therapy (i.e., a supplemental treatment) for amphetamine addiction.[sources 8] Exercise leads to better treatment outcomes when used as an adjunct treatment, particularly for psychostimulant addictions. In particular, aerobic exercise decreases psychostimulant self-administration, reduces the reinstatement (i.e., relapse) of drug-seeking, and induces increased dopamine receptor D2 (DRD2) density in the striatum. This is the opposite of pathological stimulant use, which induces decreased striatal DRD2 density. One review noted that exercise may also prevent the development of a drug addiction by altering ΔFosB or c-Fos immunoreactivity in the striatum or other parts of the reward system.
|Form of neuroplasticity
or behavioral plasticity
|Type of reinforcer||Sources|
|Opiates||Psychostimulants||High fat or sugar food||Sexual intercourse||Physical exercise
|ΔFosB expression in
nucleus accumbens D1-type MSNs
|Escalation of intake||Yes||Yes||Yes|||
conditioned place preference
|Reinstatement of drug-seeking behavior||↑||↑||↓||↓|||
in the nucleus accumbens
|Sensitized dopamine response
in the nucleus accumbens
|Altered striatal dopamine signaling||↓DRD2, ↑DRD3||↑DRD1, ↓DRD2, ↑DRD3||↑DRD1, ↓DRD2, ↑DRD3||↑DRD2||↑DRD2|||
|Altered striatal opioid signaling||No change or
|↑μ-opioid receptors||↑μ-opioid receptors||No change||No change|||
|Changes in striatal opioid peptides||↑dynorphin
No change: enkephalin
|Mesocorticolimbic synaptic plasticity|
|Number of dendrites in the nucleus accumbens||↓||↑||↑|||
|Dendritic spine density in
the nucleus accumbens
Drug tolerance develops rapidly in amphetamine abuse (i.e., recreational amphetamine use), so periods of extended abuse require increasingly larger doses of the drug in order to achieve the same effect. According to a Cochrane review on withdrawal in individuals who compulsively use amphetamine and methamphetamine, "when chronic heavy users abruptly discontinue amphetamine use, many report a time-limited withdrawal syndrome that occurs within 24 hours of their last dose." This review noted that withdrawal symptoms in chronic, high-dose users are frequent, occurring in roughly 88% of cases, and persist for 3–4 weeks with a marked "crash" phase occurring during the first week. Amphetamine withdrawal symptoms can include anxiety, drug craving, depressed mood, fatigue, increased appetite, increased movement or decreased movement, lack of motivation, sleeplessness or sleepiness, and lucid dreams. The review indicated that the severity of withdrawal symptoms is positively correlated with the age of the individual and the extent of their dependence. Mild withdrawal symptoms from the discontinuation of amphetamine treatment at therapeutic doses can be avoided by tapering the dose.
An amphetamine overdose can lead to many different symptoms, but is rarely fatal with appropriate care. The severity of overdose symptoms increases with dosage and decreases with drug tolerance to amphetamine. Tolerant individuals have been known to take as much as 5 grams of amphetamine in a day, which is roughly 100 times the maximum daily therapeutic dose. Symptoms of a moderate and extremely large overdose are listed below; fatal amphetamine poisoning usually also involves convulsions and coma. In 2013, overdose on amphetamine, methamphetamine, and other compounds implicated in an "amphetamine use disorder" resulted in an estimated 3,788 deaths worldwide (3,425–4,145 deaths, 95% confidence).[note 12]
|System||Minor or moderate overdose||Severe overdose[sources 10]|
In rodents and primates, sufficiently high doses of amphetamine cause dopaminergic neurotoxicity, or damage to dopamine neurons, which is characterized by dopamine terminal degeneration and reduced transporter and receptor function. There is no evidence that amphetamine is directly neurotoxic in humans. However, large doses of amphetamine may indirectly cause dopaminergic neurotoxicity as a result of hyperpyrexia, the excessive formation of reactive oxygen species, and increased autoxidation of dopamine.[sources 11] Animal models of neurotoxicity from high-dose amphetamine exposure indicate that the occurrence of hyperpyrexia (i.e., core body temperature ≥ 40 °C) is necessary for the development of amphetamine-induced neurotoxicity. Prolonged elevations of brain temperature above 40 °C likely promote the development of amphetamine-induced neurotoxicity in laboratory animals by facilitating the production of reactive oxygen species, disrupting cellular protein function, and transiently increasing blood–brain barrier permeability.
Pharmacodynamics of amphetamine in a dopamine neuron
Amphetamine, the active ingredient of Adderall, works primarily by increasing the activity of the neurotransmitters dopamine and norepinephrine in the brain. It also triggers the release of several other hormones (e.g., epinephrine) and neurotransmitters (e.g., serotonin and histamine) as well as the synthesis of certain neuropeptides (e.g., cocaine and amphetamine regulated transcript (CART) peptides). Both active ingredients of Adderall, dextroamphetamine and levoamphetamine, bind to the same biological targets, but their binding affinities (that is, potency) differ somewhat. Dextroamphetamine and levoamphetamine are both potent full agonists (activating compounds) of trace amine-associated receptor 1 (TAAR1) and interact with vesicular monoamine transporter 2 (VMAT2), with dextroamphetamine being the more potent agonist of TAAR1. Consequently, dextroamphetamine produces more CNS stimulation than levoamphetamine; however, levoamphetamine has slightly greater cardiovascular and peripheral effects. It has been reported that certain children have a better clinical response to levoamphetamine.
In the absence of amphetamine, VMAT2 will normally move monoamines (e.g., dopamine, histamine, serotonin, norepinephrine, etc.) from the intracellular fluid of a monoamine neuron into its synaptic vesicles, which store neurotransmitters for later release (via exocytosis) into the synaptic cleft. When amphetamine enters a neuron and interacts with VMAT2, the transporter reverses its direction of transport, thereby releasing stored monoamines inside synaptic vesicles back into the neuron's intracellular fluid. Meanwhile, when amphetamine activates TAAR1, the receptor causes the neuron's cell membrane-bound monoamine transporters (i.e., the dopamine transporter, norepinephrine transporter, or serotonin transporter) to either stop transporting monoamines altogether (via transporter internalization) or transport monoamines out of the neuron; in other words, the reversed membrane transporter will push dopamine, norepinephrine, and serotonin out of the neuron's intracellular fluid and into the synaptic cleft. In summary, by interacting with both VMAT2 and TAAR1, amphetamine releases neurotransmitters from synaptic vesicles (the effect from VMAT2) into the intracellular fluid where they subsequently exit the neuron through the membrane-bound, reversed monoamine transporters (the effect from TAAR1).
The oral bioavailability of amphetamine varies with gastrointestinal pH; it is well absorbed from the gut, and bioavailability is typically over 75% for dextroamphetamine. Amphetamine is a weak base with a pKa of 9.9; consequently, when the pH is basic, more of the drug is in its lipid soluble free base form, and more is absorbed through the lipid-rich cell membranes of the gut epithelium. Conversely, an acidic pH means the drug is predominantly in a water-soluble cationic (salt) form, and less is absorbed. Approximately 15–40% of amphetamine circulating in the bloodstream is bound to plasma proteins. Following absorption, amphetamine readily distributes into most tissues in the body, with high concentrations occurring in cerebrospinal fluid and brain tissue.
The half-lives of amphetamine enantiomers differ and vary with urine pH. At normal urine pH, the half-lives of dextroamphetamine and levoamphetamine are 9–11 hours and 11–14 hours, respectively. Highly acidic urine will reduce the enantiomer half-lives to 7 hours; highly alkaline urine will increase the half-lives up to 34 hours. The immediate-release and extended release variants of salts of both isomers reach peak plasma concentrations at 3 hours and 7 hours post-dose respectively. Amphetamine is eliminated via the kidneys, with 30–40% of the drug being excreted unchanged at normal urinary pH. When the urinary pH is basic, amphetamine is in its free base form, so less is excreted. When urine pH is abnormal, the urinary recovery of amphetamine may range from a low of 1% to a high of 75%, depending mostly upon whether urine is too basic or acidic, respectively. Following oral administration, amphetamine appears in urine within 3 hours. Roughly 90% of ingested amphetamine is eliminated 3 days after the last oral dose.
CYP2D6, dopamine β-hydroxylase (DBH), flavin-containing monooxygenase 3 (FMO3), butyrate-CoA ligase (XM-ligase), and glycine N-acyltransferase (GLYAT) are the enzymes known to metabolize amphetamine or its metabolites in humans.[sources 12] Amphetamine has a variety of excreted metabolic products, including 4-hydroxyamphetamine, 4-hydroxynorephedrine, 4-hydroxyphenylacetone, benzoic acid, hippuric acid, norephedrine, and phenylacetone. Among these metabolites, the active sympathomimetics are 4-hydroxyamphetamine, 4-hydroxynorephedrine, and norephedrine. The main metabolic pathways involve aromatic para-hydroxylation, aliphatic alpha- and beta-hydroxylation, N-oxidation, N-dealkylation, and deamination. The known metabolic pathways, detectable metabolites, and metabolizing enzymes in humans include the following:
Metabolic pathways of amphetamine in humans[sources 12]
The human metagenome (i.e., the genetic composition of an individual and all microorganisms that reside on or within the individual's body) varies considerably between individuals. Since the total number of microbial and viral cells in the human body (over 100 trillion) greatly outnumbers human cells (tens of trillions),[note 15] there is considerable potential for interactions between drugs and an individual's microbiome, including: drugs altering the composition of the human microbiome, drug metabolism by microbial enzymes modifying the drug's pharmacokinetic profile, and microbial drug metabolism affecting a drug's clinical efficacy and toxicity profile. The field that studies these interactions is known as pharmacomicrobiomics.Similar to most biomolecules and other orally administered xenobiotics (i.e., drugs), amphetamine is predicted to undergo promiscuous metabolism by human gastrointestinal microbiota (primarily bacteria) prior to absorption into the blood stream. The first amphetamine-metabolizing microbial enzyme, tyramine oxidase from a strain of E. coli commonly found in the human gut, was identified in 2019. This enzyme was found to metabolize amphetamine, tyramine, and phenethylamine with roughly the same binding affinity for all three compounds.
Richwood Pharmaceuticals, which later merged with Shire plc, introduced the current Adderall brand in 1996 as an instant-release tablet. In 2006, Shire agreed to sell rights to the Adderall name for the instant-release form of the medication to Duramed Pharmaceuticals. DuraMed Pharmaceuticals was acquired by Teva Pharmaceuticals in 2008 during their acquisition of Barr Pharmaceuticals, including Barr's Duramed division.
The first generic version of Adderall IR was introduced to market in 2002. Later on, Barr and Shire reached a settlement agreement permitting Barr to offer a generic form of the extended-release drug beginning in April 2009.
Chemically, Adderall is a mixture of four amphetamine salts; specifically, it is composed of equal parts (by mass) of amphetamine aspartate monohydrate, amphetamine sulfate, dextroamphetamine sulfate, and dextroamphetamine saccharate. This drug mixture has slightly stronger CNS effects than racemic amphetamine due to the higher proportion of dextroamphetamine. Adderall is produced as both an immediate release (IR) and extended release (XR) formulation. As of December 2013[update], ten different companies produced generic Adderall IR, while Teva Pharmaceutical Industries, Actavis, and Barr Pharmaceuticals manufactured generic Adderall XR. As of 2013[update], Shire plc, the company that held the original patent for Adderall and Adderall XR, still manufactured brand name Adderall XR, but not Adderall IR.
Adderall is one of several formulations of pharmaceutical amphetamine, including singular or mixed enantiomers and as an enantiomer prodrug. The table below compares these medications (based on US approved forms):
in equal doses
|(g/mol)||(percent)||(30 mg dose)|
|25%||amphetamine aspartate monohydrate||(C9H13N)•C4H7NO4•H2O|
|amphetamine base suspension[note 19]||C9H13N|
The pharmaceutical company Rexar reformulated their popular weight loss drug Obetrol following its mandatory withdrawal from the market in 1973 under the Kefauver Harris Amendment to the Federal Food, Drug, and Cosmetic Act due to the results of the Drug Efficacy Study Implementation (DESI) program (which indicated a lack of efficacy). The new formulation simply replaced the two methamphetamine components with dextroamphetamine and amphetamine components of the same weight (the other two original dextroamphetamine and amphetamine components were preserved), preserved the Obetrol branding, and despite it utterly lacking FDA approval, it still made it onto the market and was marketed and sold by Rexar for a number of years.
In 1994 Richwood Pharmaceuticals acquired Rexar and began promoting Obetrol as a treatment for ADHD (and later narcolepsy as well), now marketed under the new brand name of Adderall, a contraction of the phrase "A.D.D. for All" intended to convey that "it was meant to be kind of an inclusive thing" for marketing purposes. The FDA cited the company for numerous significant CGMP violations related to Obetrol discovered during routine inspections following the acquisition (including issuing a formal warning letter for the violations), then later issued a second formal warning letter to Richwood Pharmaceuticals specifically due to violations of "the new drug and misbranding provisions of the FD&C Act". Following extended discussions with Richwood Pharmaceuticals regarding the resolution of a large number of issues related to the company's numerous violations of FDA regulations, the FDA formally approved the first Obetrol labeling/sNDA revisions in 1996, including a name change to Adderall and a restoration of its status as an approved drug product. In 1997 Richwood Pharmaceuticals was acquired by Shire Pharmaceuticals in a $186 million transaction.
Amphetamine, in the singular form, properly applies to the racemate of 2-amino-1-phenylpropane. ... In its broadest context, however, the term [amphetamines] can even embrace a large number of structurally and pharmacologically related substances.
In principle, INNs are selected only for the active part of the molecule which is usually the base, acid or alcohol. In some cases, however, the active molecules need to be expanded for various reasons, such as formulation purposes, bioavailability or absorption rate. In 1975 the experts designated for the selection of INN decided to adopt a new policy for naming such molecules. In future, names for different salts or esters of the same active substance should differ only with regard to the inactive moiety of the molecule. ... The latter are called modified INNs (INNMs).
Mixed enantiomers/mixed salts amphetamine (3:1 d:l isomers)
Stimulant misuse appears to occur both for performance enhancement and their euphorogenic effects, the latter being related to the intrinsic properties of the stimulants (e.g., IR versus ER profile) ...
Although useful in the treatment of ADHD, stimulants are controlled II substances with a history of preclinical and human studies showing potential abuse liability.
Therapeutic (relatively low) doses of psychostimulants, such as methylphenidate and amphetamine, improve performance on working memory tasks both in normal subjects and those with ADHD. ... stimulants act not only on working memory function, but also on general levels of arousal and, within the nucleus accumbens, improve the saliency of tasks. Thus, stimulants improve performance on effortful but tedious tasks ... through indirect stimulation of dopamine and norepinephrine receptors. ...
Beyond these general permissive effects, dopamine (acting via D1 receptors) and norepinephrine (acting at several receptors) can, at optimal levels, enhance working memory and aspects of attention.
Amphetamines and caffeine are stimulants that increase alertness, improve focus, decrease reaction time, and delay fatigue, allowing for an increased intensity and duration of training ...
Physiologic and performance effects
• Amphetamines increase dopamine/norepinephrine release and inhibit their reuptake, leading to central nervous system (CNS) stimulation
• Amphetamines seem to enhance athletic performance in anaerobic conditions 39 40
• Improved reaction time
• Increased muscle strength and delayed muscle fatigue
• Increased acceleration
• Increased alertness and attention to task
A minority of individuals who use amphetamines develop full-blown psychosis requiring care at emergency departments or psychiatric hospitals. In such cases, symptoms of amphetamine psychosis commonly include paranoid and persecutory delusions as well as auditory and visual hallucinations in the presence of extreme agitation. More common (about 18%) is for frequent amphetamine users to report psychotic symptoms that are sub-clinical and that do not require high-intensity intervention ...
About 5–15% of the users who develop an amphetamine psychosis fail to recover completely (Hofmann 1983) ...
Findings from one trial indicate use of antipsychotic medications effectively resolves symptoms of acute amphetamine psychosis.
psychotic symptoms of individuals with amphetamine psychosis may be due exclusively to heavy use of the drug or heavy use of the drug may exacerbate an underlying vulnerability to schizophrenia.
Such agents also have important therapeutic uses; cocaine, for example, is used as a local anesthetic (Chapter 2), and amphetamines and methylphenidate are used in low doses to treat attention deficit hyperactivity disorder and in higher doses to treat narcolepsy (Chapter 12). Despite their clinical uses, these drugs are strongly reinforcing, and their long-term use at high doses is linked with potential addiction, especially when they are rapidly administered or when high-potency forms are given.
When oral formulations of psychostimulants are used at recommended doses and frequencies, they are unlikely to yield effects consistent with abuse potential in patients with ADHD.
VMAT2 is the CNS vesicular transporter for not only the biogenic amines DA, NE, EPI, 5-HT, and HIS, but likely also for the trace amines TYR, PEA, and thyronamine (THYR) ... [Trace aminergic] neurons in mammalian CNS would be identifiable as neurons expressing VMAT2 for storage, and the biosynthetic enzyme aromatic amino acid decarboxylase (AADC).
Basal ganglia regions like the right globus pallidus, the right putamen, and the nucleus caudatus are structurally affected in children with ADHD. These changes and alterations in limbic regions like ACC and amygdala are more pronounced in non-treated populations and seem to diminish over time from child to adulthood. Treatment seems to have positive effects on brain structure.
Several other studies,[97-101] including a meta-analytic review and a retrospective study, suggested that stimulant therapy in childhood is associated with a reduced risk of subsequent substance use, cigarette smoking and alcohol use disorders. ... Recent studies have demonstrated that stimulants, along with the non-stimulants atomoxetine and extended-release guanfacine, are continuously effective for more than 2-year treatment periods with few and tolerable adverse effects. The effectiveness of long-term therapy includes not only the core symptoms of ADHD, but also improved quality of life and academic achievements. The most concerning short-term adverse effects of stimulants, such as elevated blood pressure and heart rate, waned in long-term follow-up studies. ... The current data do not support the potential impact of stimulants on the worsening or development of tics or substance abuse into adulthood. In the longest follow-up study (of more than 10 years), lifetime stimulant treatment for ADHD was effective and protective against the development of adverse psychiatric disorders.
Ongoing research has provided answers to many of the parents' concerns, and has confirmed the effectiveness and safety of the long-term use of medication.
The highest proportion of improved outcomes was reported with combination treatment (83% of outcomes). Among significantly improved outcomes, the largest effect sizes were found for combination treatment. The greatest improvements were associated with academic, self-esteem, or social function outcomes.
Only one paper53 examining outcomes beyond 36 months met the review criteria. ... There is high level evidence suggesting that pharmacological treatment can have a major beneficial effect on the core symptoms of ADHD (hyperactivity, inattention, and impulsivity) in approximately 80% of cases compared with placebo controls, in the short term.
The procognitive actions of psychostimulants are only associated with low doses. Surprisingly, despite nearly 80 years of clinical use, the neurobiology of the procognitive actions of psychostimulants has only recently been systematically investigated. Findings from this research unambiguously demonstrate that the cognition-enhancing effects of psychostimulants involve the preferential elevation of catecholamines in the PFC and the subsequent activation of norepinephrine α2 and dopamine D1 receptors. ... This differential modulation of PFC-dependent processes across dose appears to be associated with the differential involvement of noradrenergic α2 versus α1 receptors. Collectively, this evidence indicates that at low, clinically relevant doses, psychostimulants are devoid of the behavioral and neurochemical actions that define this class of drugs and instead act largely as cognitive enhancers (improving PFC-dependent function). ... In particular, in both animals and humans, lower doses maximally improve performance in tests of working memory and response inhibition, whereas maximal suppression of overt behavior and facilitation of attentional processes occurs at higher doses.
Specifically, in a set of experiments limited to high-quality designs, we found significant enhancement of several cognitive abilities. ... The results of this meta-analysis ... do confirm the reality of cognitive enhancing effects for normal healthy adults in general, while also indicating that these effects are modest in size.
Amphetamine has been shown to improve consolidation of information (0.02 ≥ P ≤ 0.05), leading to improved recall.
Dopamine acts in the nucleus accumbens to attach motivational significance to stimuli associated with reward.
misuse of prescription stimulants has become a serious problem on college campuses across the US and has been recently documented in other countries as well. ... Indeed, large numbers of students claim to have engaged in the nonmedical use of prescription stimulants, which is reflected in lifetime prevalence rates of prescription stimulant misuse ranging from 5% to nearly 34% of students.
Overall, the data suggest that ADHD medication misuse and diversion are common health care problems for stimulant medications, with the prevalence believed to be approximately 5% to 10% of high school students and 5% to 35% of college students, depending on the study.
In 1980, Chandler and Blair47 showed significant increases in knee extension strength, acceleration, anaerobic capacity, time to exhaustion during exercise, pre-exercise and maximum heart rates, and time to exhaustion during maximal oxygen consumption (VO2 max) testing after administration of 15 mg of dextroamphetamine versus placebo. Most of the information to answer this question has been obtained in the past decade through studies of fatigue rather than an attempt to systematically investigate the effect of ADHD drugs on exercise.
In high-ambient temperatures, dopaminergic manipulations clearly improve performance. The distribution of the power output reveals that after dopamine reuptake inhibition, subjects are able to maintain a higher power output compared with placebo. ... Dopaminergic drugs appear to override a safety switch and allow athletes to use a reserve capacity that is 'off-limits' in a normal (placebo) situation.
Manipulations of dopaminergic signaling profoundly influence interval timing, leading to the hypothesis that dopamine influences internal pacemaker, or "clock," activity. For instance, amphetamine, which increases concentrations of dopamine at the synaptic cleft advances the start of responding during interval timing, whereas antagonists of D2 type dopamine receptors typically slow timing;... Depletion of dopamine in healthy volunteers impairs timing, while amphetamine releases synaptic dopamine and speeds up timing.
Aside from accounting for the reduced performance of mentally fatigued participants, this model rationalizes the reduced RPE and hence improved cycling time trial performance of athletes using a glucose mouthwash (Chambers et al., 2009) and the greater power output during a RPE matched cycling time trial following amphetamine ingestion (Swart, 2009). ... Dopamine stimulating drugs are known to enhance aspects of exercise performance (Roelands et al., 2008)
This indicates that subjects did not feel they were producing more power and consequently more heat. The authors concluded that the "safety switch" or the mechanisms existing in the body to prevent harmful effects are overridden by the drug administration (Roelands et al., 2008b). Taken together, these data indicate strong ergogenic effects of an increased DA concentration in the brain, without any change in the perception of effort.
statements on package inserts are not intended to limit medical practice. Rather they are intended to limit claims by pharmaceutical companies. ... the FDA asserts explicitly, and the courts have upheld that clinical decisions are to be made by physicians and patients in individual situations.
Table 2. Decongestants Causing Rhinitis Medicamentosa
– Nasal decongestants:
In these studies, amphetamine was given in consecutively higher doses until psychosis was precipitated, often after 100–300 mg of amphetamine ... Secondly, psychosis has been viewed as an adverse event, although rare, in children with ADHD who have been treated with amphetamine
This study demonstrates that humans, like nonhumans, prefer a place associated with amphetamine administration. These findings support the idea that subjective responses to a drug contribute to its ability to establish place conditioning.
Despite the importance of numerous psychosocial factors, at its core, drug addiction involves a biological process: the ability of repeated exposure to a drug of abuse to induce changes in a vulnerable brain that drive the compulsive seeking and taking of drugs, and loss of control over drug use, that define a state of addiction. ... A large body of literature has demonstrated that such ΔFosB induction in D1-type [nucleus accumbens] neurons increases an animal's sensitivity to drug as well as natural rewards and promotes drug self-administration, presumably through a process of positive reinforcement ... Another ΔFosB target is cFos: as ΔFosB accumulates with repeated drug exposure it represses c-Fos and contributes to the molecular switch whereby ΔFosB is selectively induced in the chronic drug-treated state.41. ... Moreover, there is increasing evidence that, despite a range of genetic risks for addiction across the population, exposure to sufficiently high doses of a drug for long periods of time can transform someone who has relatively lower genetic loading into an addict.
Substance-use disorder: A diagnostic term in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) referring to recurrent use of alcohol or other drugs that causes clinically and functionally significant impairment, such as health problems, disability, and failure to meet major responsibilities at work, school, or home. Depending on the level of severity, this disorder is classified as mild, moderate, or severe.
Addiction: A term used to indicate the most severe, chronic stage of substance-use disorder, in which there is a substantial loss of self-control, as indicated by compulsive drug taking despite the desire to stop taking the drug. In the DSM-5, the term addiction is synonymous with the classification of severe substance-use disorder.
[Psychostimulants] increase cAMP levels in striatum, which activates protein kinase A (PKA) and leads to phosphorylation of its targets. This includes the cAMP response element binding protein (CREB), the phosphorylation of which induces its association with the histone acetyltransferase, CREB binding protein (CBP) to acetylate histones and facilitate gene activation. This is known to occur on many genes including fosB and c-fos in response to psychostimulant exposure. ΔFosB is also upregulated by chronic psychostimulant treatments, and is known to activate certain genes (eg, cdk5) and repress others (eg, c-fos) where it recruits HDAC1 as a corepressor. ... Chronic exposure to psychostimulants increases glutamatergic [signaling] from the prefrontal cortex to the NAc. Glutamatergic signaling elevates Ca2+ levels in NAc postsynaptic elements where it activates CaMK (calcium/calmodulin protein kinases) signaling, which, in addition to phosphorylating CREB, also phosphorylates HDAC5.
Coincident and convergent input often induces plasticity on a postsynaptic neuron. The NAc integrates processed information about the environment from basolateral amygdala, hippocampus, and prefrontal cortex (PFC), as well as projections from midbrain dopamine neurons. Previous studies have demonstrated how dopamine modulates this integrative process. For example, high frequency stimulation potentiates hippocampal inputs to the NAc while simultaneously depressing PFC synapses (Goto and Grace, 2005). The converse was also shown to be true; stimulation at PFC potentiates PFC–NAc synapses but depresses hippocampal–NAc synapses. In light of the new functional evidence of midbrain dopamine/glutamate co-transmission (references above), new experiments of NAc function will have to test whether midbrain glutamatergic inputs bias or filter either limbic or cortical inputs to guide goal-directed behavior.
Most addictive drugs increase extracellular concentrations of dopamine (DA) in nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), projection areas of mesocorticolimbic DA neurons and key components of the "brain reward circuit". Amphetamine achieves this elevation in extracellular levels of DA by promoting efflux from synaptic terminals. ... Chronic exposure to amphetamine induces a unique transcription factor delta FosB, which plays an essential role in long-term adaptive changes in the brain.
ΔFosB serves as one of the master control proteins governing this structural plasticity. ... ΔFosB also represses G9a expression, leading to reduced repressive histone methylation at the cdk5 gene. The net result is gene activation and increased CDK5 expression. ... In contrast, ΔFosB binds to the c-fos gene and recruits several co-repressors, including HDAC1 (histone deacetylase 1) and SIRT 1 (sirtuin 1). ... The net result is c-fos gene repression.
The 35-37 kD ΔFosB isoforms accumulate with chronic drug exposure due to their extraordinarily long half-lives. ... As a result of its stability, the ΔFosB protein persists in neurons for at least several weeks after cessation of drug exposure. ... ΔFosB overexpression in nucleus accumbens induces NFκB ... In contrast, the ability of ΔFosB to repress the c-Fos gene occurs in concert with the recruitment of a histone deacetylase and presumably several other repressive proteins such as a repressive histone methyltransferase
Recent evidence has shown that ΔFosB also represses the c-fos gene that helps create the molecular switch—from the induction of several short-lived Fos family proteins after acute drug exposure to the predominant accumulation of ΔFosB after chronic drug exposure
ΔFosB is an essential transcription factor implicated in the molecular and behavioral pathways of addiction following repeated drug exposure.
ΔFosB serves as one of the master control proteins governing this structural plasticity.
Similar to environmental enrichment, studies have found that exercise reduces self-administration and relapse to drugs of abuse (Cosgrove et al., 2002; Zlebnik et al., 2010). There is also some evidence that these preclinical findings translate to human populations, as exercise reduces withdrawal symptoms and relapse in abstinent smokers (Daniel et al., 2006; Prochaska et al., 2008), and one drug recovery program has seen success in participants that train for and compete in a marathon as part of the program (Butler, 2005). ... In humans, the role of dopamine signaling in incentive-sensitization processes has recently been highlighted by the observation of a dopamine dysregulation syndrome in some patients taking dopaminergic drugs. This syndrome is characterized by a medication-induced increase in (or compulsive) engagement in non-drug rewards such as gambling, shopping, or sex (Evans et al., 2006; Aiken, 2007; Lader, 2008).
These findings suggest that exercise may "magnitude"-dependently prevent the development of an addicted phenotype possibly by blocking/reversing behavioral and neuroadaptive changes that develop during and following extended access to the drug. ... Exercise has been proposed as a treatment for drug addiction that may reduce drug craving and risk of relapse. Although few clinical studies have investigated the efficacy of exercise for preventing relapse, the few studies that have been conducted generally report a reduction in drug craving and better treatment outcomes ... Taken together, these data suggest that the potential benefits of exercise during relapse, particularly for relapse to psychostimulants, may be mediated via chromatin remodeling and possibly lead to greater treatment outcomes.
Collectively, these findings demonstrate that exercise may serve as a substitute or competition for drug abuse by changing ΔFosB or cFos immunoreactivity in the reward system to protect against later or previous drug use. ... The postulate that exercise serves as an ideal intervention for drug addiction has been widely recognized and used in human and animal rehabilitation.
The limited research conducted suggests that exercise may be an effective adjunctive treatment for SUDs. In contrast to the scarce intervention trials to date, a relative abundance of literature on the theoretical and practical reasons supporting the investigation of this topic has been published. ... numerous theoretical and practical reasons support exercise-based treatments for SUDs, including psychological, behavioral, neurobiological, nearly universal safety profile, and overall positive health effects.
Currently, cognitive–behavioral therapies are the most successful treatment available for preventing the relapse of psychostimulant use.
ΔFosB has been linked directly to several addiction-related behaviors ... Importantly, genetic or viral overexpression of ΔJunD, a dominant negative mutant of JunD which antagonizes ΔFosB- and other AP-1-mediated transcriptional activity, in the NAc or OFC blocks these key effects of drug exposure14,22–24. This indicates that ΔFosB is both necessary and sufficient for many of the changes wrought in the brain by chronic drug exposure. ΔFosB is also induced in D1-type NAc MSNs by chronic consumption of several natural rewards, including sucrose, high fat food, sex, wheel running, where it promotes that consumption14,26–30. This implicates ΔFosB in the regulation of natural rewards under normal conditions and perhaps during pathological addictive-like states.
It has been found that deltaFosB gene in the NAc is critical for reinforcing effects of sexual reward. Pitchers and colleagues (2010) reported that sexual experience was shown to cause DeltaFosB accumulation in several limbic brain regions including the NAc, medial pre-frontal cortex, VTA, caudate, and putamen, but not the medial preoptic nucleus. ... these findings support a critical role for DeltaFosB expression in the NAc in the reinforcing effects of sexual behavior and sexual experience-induced facilitation of sexual performance. ... both drug addiction and sexual addiction represent pathological forms of neuroplasticity along with the emergence of aberrant behaviors involving a cascade of neurochemical changes mainly in the brain's rewarding circuitry.
Pharmacologic treatment for psychostimulant addiction is generally unsatisfactory. As previously discussed, cessation of cocaine use and the use of other psychostimulants in dependent individuals does not produce a physical withdrawal syndrome but may produce dysphoria, anhedonia, and an intense desire to reinitiate drug use.
To date, no pharmacological treatment has been approved for [addiction], and psychotherapy remains the mainstay of treatment. ... Results of this review do not support the use of psychostimulant medications at the tested doses as a replacement therapy
Despite concerted efforts to identify a pharmacotherapy for managing stimulant use disorders, no widely effective medications have been approved.
When considered together with the rapidly growing literature in the field a compelling case emerges in support of developing TAAR1-selective agonists as medications for preventing relapse to psychostimulant abuse.
Existing data provided robust preclinical evidence supporting the development of TAAR1 agonists as potential treatment for psychostimulant abuse and addiction.
There is accelerating evidence that physical exercise is a useful treatment for preventing and reducing drug addiction ... In some individuals, exercise has its own rewarding effects, and a behavioral economic interaction may occur, such that physical and social rewards of exercise can substitute for the rewarding effects of drug abuse. ... The value of this form of treatment for drug addiction in laboratory animals and humans is that exercise, if it can substitute for the rewarding effects of drugs, could be self-maintained over an extended period of time. Work to date in [laboratory animals and humans] regarding exercise as a treatment for drug addiction supports this hypothesis. ... Animal and human research on physical exercise as a treatment for stimulant addiction indicates that this is one of the most promising treatments on the horizon.
The prevalence of this withdrawal syndrome is extremely common (Cantwell 1998; Gossop 1982) with 87.6% of 647 individuals with amphetamine dependence reporting six or more signs of amphetamine withdrawal listed in the DSM when the drug is not available (Schuckit 1999) ... The severity of withdrawal symptoms is greater in amphetamine dependent individuals who are older and who have more extensive amphetamine use disorders (McGregor 2005). Withdrawal symptoms typically present within 24 hours of the last use of amphetamine, with a withdrawal syndrome involving two general phases that can last 3 weeks or more. The first phase of this syndrome is the initial "crash" that resolves within about a week (Gossop 1982;McGregor 2005) ...
Amphetamine, dextroamphetamine, and methylphenidate act as substrates for the cellular monoamine transporter, especially the dopamine transporter (DAT) and less so the norepinephrine (NET) and serotonin transporter. The mechanism of toxicity is primarily related to excessive extracellular dopamine, norepinephrine, and serotonin.
Amphetamine use disorders ... 3,788 (3,425–4,145)
Hyperthermia alone does not produce amphetamine-like neurotoxicity but AMPH and METH exposures that do not produce hyperthermia (≥40°C) are minimally neurotoxic. Hyperthermia likely enhances AMPH and METH neurotoxicity directly through disruption of protein function, ion channels and enhanced ROS production. ... The hyperthermia and the hypertension produced by high doses amphetamines are a primary cause of transient breakdowns in the blood-brain barrier (BBB) resulting in concomitant regional neurodegeneration and neuroinflammation in laboratory animals. ... In animal models that evaluate the neurotoxicity of AMPH and METH, it is quite clear that hyperthermia is one of the essential components necessary for the production of histological signs of dopamine terminal damage and neurodegeneration in cortex, striatum, thalamus and hippocampus.
Direct toxic damage to vessels seems unlikely because of the dilution that occurs before the drug reaches the cerebral circulation.
Unlike cocaine and amphetamine, methamphetamine is directly toxic to midbrain dopamine neurons.
Zinc binds at ... extracellular sites of the DAT , serving as a DAT inhibitor. In this context, controlled double-blind studies in children are of interest, which showed positive effects of zinc [supplementation] on symptoms of ADHD [105,106]. It should be stated that at this time [supplementation] with zinc is not integrated in any ADHD treatment algorithm.
They did not confirm the predicted straightforward relationship between uptake and release, but rather that some compounds including AMPH were better releasers than substrates for uptake. Zinc, moreover, stimulates efflux of intracellular [3H]DA despite its concomitant inhibition of uptake (Scholze et al., 2002).
The human dopamine transporter (hDAT) contains an endogenous high affinity Zn2+ binding site with three coordinating residues on its extracellular face (His193, His375, and Glu396). ... Although Zn2+ inhibited uptake, Zn2+ facilitated [3H]MPP+ release induced by amphetamine, MPP+, or K+-induced depolarization specifically at hDAT but not at the human serotonin and the norepinephrine transporter (hNET). ... Surprisingly, this amphetamine-elicited efflux was markedly enhanced, rather than inhibited, by the addition of 10 μM Zn2+ to the superfusion buffer (Fig. 2 A, open squares). We stress that Zn2+ per se did not affect basal efflux (Fig. 2 A). ... In many brain regions, Zn2+ is stored in synaptic vesicles and co-released together with glutamate; under basal conditions, the extracellular levels of Zn2+ are low (∼10 nM; see Refs. 39, 40). Upon neuronal stimulation, however, Zn2+ is co-released with the neurotransmitters and, consequently, the free Zn2+ concentration may transiently reach values that range from 10–20 μM (10) up to 300 μM (11). The concentrations of Zn2+ shown in this study, required for the stimulation of dopamine release (as well as inhibition of uptake), covered this physiologically relevant range, with maximum stimulation occurring at 3–30 μM. It is therefore conceivable that the action of Zn2+ on hDAT does not merely reflect a biochemical peculiarity but that it is physiologically relevant. ... Thus, when Zn2+ is co-released with glutamate, it may greatly augment the efflux of dopamine.
Although we did not find a sufficient number of studies suitable for a meta-analysis of PEA and ADHD, three studies20,57,58 confirmed that urinary levels of PEA were significantly lower in patients with ADHD compared with controls. ... Administration of D-amphetamine and methylphenidate resulted in a markedly increased urinary excretion of PEA,20,60 suggesting that ADHD treatments normalize PEA levels. ... Similarly, urinary biogenic trace amine PEA levels could be a biomarker for the diagnosis of ADHD,20,57,58 for treatment efficacy,20,60 and associated with symptoms of inattentivenesss.59 ... With regard to zinc supplementation, a placebo controlled trial reported that doses up to 30 mg/day of zinc were safe for at least 8 weeks, but the clinical effect was equivocal except for the finding of a 37% reduction in amphetamine optimal dose with 30 mg per day of zinc.110
Despite the challenges in determining synaptic vesicle pH, the proton gradient across the vesicle membrane is of fundamental importance for its function. Exposure of isolated catecholamine vesicles to protonophores collapses the pH gradient and rapidly redistributes transmitter from inside to outside the vesicle. ... Amphetamine and its derivatives like methamphetamine are weak base compounds that are the only widely used class of drugs known to elicit transmitter release by a non-exocytic mechanism. As substrates for both DAT and VMAT, amphetamines can be taken up to the cytosol and then sequestered in vesicles, where they act to collapse the vesicular pH gradient.
Three important new aspects of TAs action have recently emerged: (a) inhibition of firing due to increased release of dopamine; (b) reduction of D2 and GABAB receptor-mediated inhibitory responses (excitatory effects due to disinhibition); and (c) a direct TA1 receptor-mediated activation of GIRK channels which produce cell membrane hyperpolarization.
• tonically activates inwardly rectifying K(+) channels, which reduces the basal firing frequency of dopamine (DA) neurons of the ventral tegmental area (VTA)
AMPH also increases intracellular calcium (Gnegy et al., 2004) that is associated with calmodulin/CamKII activation (Wei et al., 2007) and modulation and trafficking of the DAT (Fog et al., 2006; Sakrikar et al., 2012). ... For example, AMPH increases extracellular glutamate in various brain regions including the striatum, VTA and NAc (Del Arco et al., 1999; Kim et al., 1981; Mora and Porras, 1993; Xue et al., 1996), but it has not been established whether this change can be explained by increased synaptic release or by reduced clearance of glutamate. ... DHK-sensitive, EAAT2 uptake was not altered by AMPH (Figure 1A). The remaining glutamate transport in these midbrain cultures is likely mediated by EAAT3 and this component was significantly decreased by AMPH
AMPH and METH also stimulate DA efflux, which is thought to be a crucial element in their addictive properties , although the mechanisms do not appear to be identical for each drug . These processes are PKCβ– and CaMK–dependent [72, 82], and PKCβ knock-out mice display decreased AMPH-induced efflux that correlates with reduced AMPH-induced locomotion .
Duration of effect varies depending on agent and urine pH. Excretion is enhanced in more acidic urine. Half-life is 7 to 34 hours and is, in part, dependent on urine pH (half-life is longer with alkaline urine). ... Amphetamines are distributed into most body tissues with high concentrations occurring in the brain and CSF. Amphetamine appears in the urine within about 3 hours following oral administration. ... Three days after a dose of (+ or -)-amphetamine, human subjects had excreted 91% of the (14)C in the urine
The simplest unsubstituted phenylisopropylamine, 1-phenyl-2-aminopropane, or amphetamine, serves as a common structural template for hallucinogens and psychostimulants. Amphetamine produces central stimulant, anorectic, and sympathomimetic actions, and it is the prototype member of this class (39). ... The phase 1 metabolism of amphetamine analogs is catalyzed by two systems: cytochrome P450 and flavin monooxygenase. ... Amphetamine can also undergo aromatic hydroxylation to p-hydroxyamphetamine. ... Subsequent oxidation at the benzylic position by DA β-hydroxylase affords p-hydroxynorephedrine. Alternatively, direct oxidation of amphetamine by DA β-hydroxylase can afford norephedrine.
Dopamine-β-hydroxylase catalyzed the removal of the pro-R hydrogen atom and the production of 1-norephedrine, (2S,1R)-2-amino-1-hydroxyl-1-phenylpropane, from d-amphetamine.
Hydroxyamphetamine was administered orally to five human subjects ... Since conversion of hydroxyamphetamine to hydroxynorephedrine occurs in vitro by the action of dopamine-β-oxidase, a simple method is suggested for measuring the activity of this enzyme and the effect of its inhibitors in man. ... The lack of effect of administration of neomycin to one patient indicates that the hydroxylation occurs in body tissues. ... a major portion of the β-hydroxylation of hydroxyamphetamine occurs in non-adrenal tissue. Unfortunately, at the present time one cannot be completely certain that the hydroxylation of hydroxyamphetamine in vivo is accomplished by the same enzyme which converts dopamine to noradrenaline.
Figure 1. Glycine conjugation of benzoic acid. The glycine conjugation pathway consists of two steps. First benzoate is ligated to CoASH to form the high-energy benzoyl-CoA thioester. This reaction is catalyzed by the HXM-A and HXM-B medium-chain acid:CoA ligases and requires energy in the form of ATP. ... The benzoyl-CoA is then conjugated to glycine by GLYAT to form hippuric acid, releasing CoASH. In addition to the factors listed in the boxes, the levels of ATP, CoASH, and glycine may influence the overall rate of the glycine conjugation pathway.
The biologic significance of the different levels of serum DβH activity was studied in two ways. First, in vivo ability to β-hydroxylate the synthetic substrate hydroxyamphetamine was compared in two subjects with low serum DβH activity and two subjects with average activity. ... In one study, hydroxyamphetamine (Paredrine), a synthetic substrate for DβH, was administered to subjects with either low or average levels of serum DβH activity. The percent of the drug hydroxylated to hydroxynorephedrine was comparable in all subjects (6.5-9.62) (Table 3).
In species where aromatic hydroxylation of amphetamine is the major metabolic pathway, p-hydroxyamphetamine (POH) and p-hydroxynorephedrine (PHN) may contribute to the pharmacological profile of the parent drug. ... The location of the p-hydroxylation and β-hydroxylation reactions is important in species where aromatic hydroxylation of amphetamine is the predominant pathway of metabolism. Following systemic administration of amphetamine to rats, POH has been found in urine and in plasma.
The observed lack of a significant accumulation of PHN in brain following the intraventricular administration of (+)-amphetamine and the formation of appreciable amounts of PHN from (+)-POH in brain tissue in vivo supports the view that the aromatic hydroxylation of amphetamine following its systemic administration occurs predominantly in the periphery, and that POH is then transported through the blood-brain barrier, taken up by noradrenergic neurones in brain where (+)-POH is converted in the storage vesicles by dopamine β-hydroxylase to PHN.
The metabolism of p-OHA to p-OHNor is well documented and dopamine-β hydroxylase present in noradrenergic neurons could easily convert p-OHA to p-OHNor after intraventricular administration.
The hundred trillion microbes and viruses residing in every human body, which outnumber human cells and contribute at least 100 times more genes than those encoded on the human genome (Ley et al., 2006), offer an immense accessory pool for inter-individual genetic variation that has been underestimated and largely unexplored (Savage, 1977; Medini et al., 2008; Minot et al., 2011; Wylie et al., 2012). ... Meanwhile, a wealth of literature has long been available about the biotransformation of xenobiotics, notably by gut bacteria (reviewed in Sousa et al., 2008; Rizkallah et al., 2010; Johnson et al., 2012; Haiser and Turnbaugh, 2013). This valuable information is predominantly about drug metabolism by unknown human-associated microbes; however, only a few cases of inter-individual microbiome variations have been documented [e.g., digoxin (Mathan et al., 1989) and acetaminophen (Clayton et al., 2009)].
The composition of the microbiome varies by anatomical site (Figure 1). The primary determinant of community composition is anatomical location: interpersonal variation is substantial23,24 and is higher than the temporal variability seen at most sites in a single individual25. ... How does the microbiome affect the pharmacology of medications? Can we "micro-type" people to improve pharmacokinetics and/or reduce toxicity? Can we manipulate the microbiome to improve pharmacokinetic stability?
Some metagenomic studies have suggested that less than 10% of the cells that comprise our bodies are Homo sapiens cells. The remaining 90% are bacterial cells. The description of this so-called human microbiome is of great interest and importance for several reasons. For one, it helps us redefine what a biological individual is. We suggest that a human individual is now best described as a super-individual in which a large number of different species (including Homo sapiens) coexist.
Particularly in the case of the human gut, which harbors a large diversity of bacterial species, the differences in microbial composition can significantly alter the metabolic activity in the gut lumen.4 The differential metabolic activity due to the differences in gut microbial species has been recently linked with various metabolic disorders and diseases.5-12 In addition to the impact of gut microbial diversity or dysbiosis in various human diseases, there is an increasing amount of evidence which shows that the gut microbes can affect the bioavailability and efficacy of various orally administrated drug molecules through promiscuous enzymatic metabolism.13,14 ... The present study on the atomistic details of amphetamine binding and binding affinity to the tyramine oxidase along with the comparison with two natural substrates of this enzyme namely tyramine and phenylalanine provides strong evidence for the promiscuity‐based metabolism of amphetamine by the tyramine oxidase enzyme of E. coli. The obtained results will be crucial in designing a surrogate molecule for amphetamine that can help either in improving the efficacy and bioavailability of the amphetamine drug via competitive inhibition or in redesigning the drug for better pharmacological effects. This study will also have useful clinical implications in reducing the gut microbiota caused variation in the drug response among different populations.
WOODCLIFF LAKE, N.J., Aug. 14 /PRNewswire-FirstCall/ – Barr Pharmaceuticals, Inc. today announced that its subsidiary Duramed Pharmaceuticals, Inc. and Shire plc have signed a Product Acquisition Agreement for ADDERALL(R) (immediate-release mixed amphetamine salts) tablets and a Product Development Agreement for six proprietary products, and that its subsidiary Barr Laboratories, Inc. (Barr) has signed a Settlement and License Agreement relating to the resolution of two pending patent cases involving Shire's ADDERALL XR(R) ...