Citalopram was approved for medical use in the United States in 1998. It is available as a generic medication. In the United Kingdom, a typical dose costs less than 20 GBP per month. In the United States, it costs 50 to 100 USD per month as of 2016. In 2016, it was the 21st most prescribed medication in the United States, with more than 26 million prescriptions.
It has been shown to be effective in 85% of patients with generalized anxiety disorder, including some who had failed with other SSRIs. It also appears to be as effective as fluvoxamine and paroxetine in obsessive–compulsive disorder. Some data suggest the effectiveness of intravenous infusion of citalopram in resistant OCD.
Citalopram is well tolerated and as effective as moclobemide in social anxiety disorder. There are studies suggesting that citalopram can be useful in reducing aggressive and impulsive behavior. It appears to be superior to placebo for behavioural disturbances associated with dementia. It has also been used successfully for hypersexuality in early Alzheimer’s disease.
A meta-analysis, including studies with fluoxetine, paroxetine, sertraline, escitalopram, and citalopram versus placebo, showed SSRIs to be effective in reducing symptoms of premenstrual syndrome, whether taken continuously or just in the luteal phase.
Citalopram has produced a modest reduction in alcoholic drink intake and increase in drink-free days in studies of alcoholics, possibly by decreasing desire or reducing the reward.
A 2009 multisite randomized controlled study found no benefit and some adverse effects in autistic children from citalopram, raising doubts whether SSRIs are effective for treating repetitive behavior in children with autism.
Some research suggests citalopram interacts with cannabinoid protein-couplings in the rat brain, and this is put forward as a potential cause of some of the drug's antidepressant effect.
Citalopram is typically taken in one dose, either in the morning or evening. It can be taken with or without food. Its absorption does not increase when taken with food, but doing so can help prevent nausea. Nausea is often caused when the 5HT3 receptors actively absorb free serotonin, as this receptor is present within the digestive tract. The 5HT3 receptors stimulate vomiting. This side effect, if present, should subside as the body adjusts to the medication.
Sexual dysfunction is often a side effect with SSRIs. Specifically, common side effects include difficulty becoming aroused, lack of interest in sex, and anorgasmia (trouble achieving orgasm). One study showed, however, when remission of major depressive disorder is achieved, quality of life and sexual satisfaction is reported to be higher in spite of sexual side effects.
Citalopram theoretically causes side effects by increasing the concentration of serotonin in other parts of the body (e.g., the intestines). Other side effects, such as increased apathy and emotional flattening, may be caused by the decrease in dopamine release associated with increased serotonin. Citalopram is also a mild antihistamine, which may be responsible for some of its sedating properties.:104
Withdrawal symptoms can occur when this medicine is suddenly stopped, such as paraesthesiae, sleeping problems (difficulty sleeping and intense dreams), feeling dizzy, agitated or anxious, nausea, vomiting, tremors, confusion, sweating, headache, diarrhea, palpitations, changes in emotions, irritability, and eye or eyesight problems. Treatment with citalopram should be reduced gradually when treatment is finished.
Some people experience persistent sexual side effects after they stop taking SSRIs. This is known as Post-SSRI Sexual Dysfunction (PSSD). Common symptoms in these cases include genital anesthesia, erectile dysfunction, anhedonia, decreased libido, premature ejaculation, vaginal lubrication issues, and nipple insensitivity in women. The prevalence of PSSD is unknown, and there is no established treatment.
Abnormal heart rhythm
In August 2011, the FDA announced, “Citalopram causes dose-dependent QT interval prolongation. Citalopram should no longer be prescribed at doses greater than 40 mg per day”. A further clarification issued in March 2012 restricted the maximum dose to 20 mg for subgroups of patients, including those older than 60 years and those taking an inhibitor of cytochrome P450 2C19.7.
As with other SSRIs, citalopram can cause an increase in serum prolactin level.
Citalopram has no significant effect on insulin sensitivity in women of reproductive age and no changes in glycaemic control were seen in another trial.
Exposure in pregnancy
Antidepressant exposure (including citalopram) during pregnancy is associated with shorter duration of gestation (by three days), increased risk of preterm delivery (by 55%), lower birth weight (by 75 g), and lower Apgar scores (by <0.4 points). Antidepressant exposure is not associated with an increased risk of spontaneous abortion. It is uncertain whether there is an increased prevalence of septal heart defects among children whose mothers were prescribed an SSRI in early pregnancy.
Citalopram should not be taken with St John's wort, tryptophan or 5-HTP as the resulting drug interaction could lead to serotonin syndrome. With St John's wort, this may be caused by compounds in the plant extract reducing the efficacy of the hepaticcytochrome P450 enzymes that process citalopram. It has also been suggested that such compounds, including hypericin, hyperforin and flavonoids, could have SSRI-mimetic effects on the nervous system, although this is still subject to debate. One study found that Hypericum extracts had similar effects in treating moderate depression as citalopram, with fewer side effects.
Tryptophan and 5-HTP are precursors to serotonin. When taken with an SSRI, such as citalopram, this can lead to levels of serotonin that can be lethal. This may also be the case when SSRIs are taken with SRAs (serotonin releasing agents) such as in the case of MDMA. It is possible that SSRIs could reduce the effects associated due an SRA, since SSRIs stop the reuptake of Serotonin by blocking SERT. This would allow less serotonin in and out of the transporters, thus decreasing the likelihood of neurotoxic effects. However, these concerns are still disputed as the exact pharmacodynamic effects of citalopram and MDMA have yet to be fully identified.
Taking citalopram with omeprazole may cause higher blood levels of citalopram. This is a potentially dangerous interaction, so dosage adjustments may be needed or alternatives may be prescribed.
SSRI discontinuation syndrome has been reported when treatment is stopped. It includes sensory, gastrointestinal symptoms, dizziness, lethargy, and sleep disturbances, as well as psychological symptoms such as anxiety/agitation, irritability, and poor concentration. Electric shock-like sensations are typical for SSRI discontinuation. Tapering off citalopram therapy, as opposed to abrupt discontinuation, is recommended in order to diminish the occurrence and severity of discontinuation symptoms. Some doctors choose to switch a patient to Prozac (fluoxetine) when discontinuing citalopram as fluoxetine has a much longer half-life (i.e. stays in the body longer compared to citalopram). This may avoid many of the severe withdrawal symptoms associated with citalopram discontinuation. This can be done either by administering a single 20 mg dose of fluoxetine or by beginning on a low dosage of fluoxetine and slowly tapering down. Either of these prescriptions may be written in liquid form to allow a very slow and gradual tapering down in dosage. Alternatively, a patient wishing to stop taking citalopram may visit a compounding pharmacy where his or her prescription may be re-arranged into progressively smaller dosages.
Overdosage may result in vomiting, sedation, disturbances in heart rhythm, dizziness, sweating, nausea, tremor, and rarely amnesia, confusion, coma, or convulsions.:105 Overdose deaths have occurred, sometimes involving other drugs, but also with citalopram as the sole agent. Citalopram and N-desmethylcitalopram may be quantified in blood or plasma to confirm a diagnosis of poisoning in hospitalized patients or to assist in a medicolegal death investigation. Blood or plasma citalopram concentrations are usually in a range of 50-400 μg/l in persons receiving the drug therapeutically, 1000–3000 μg/l in patients who survive acute overdosage and 3–30 mg/l in those who do not survive. It is the most dangerous of SSRIs in overdose.
In the United States, citalopram carries a boxed warning stating it may increase suicidal thinking and behavior in those under age 24.
Citalopram is sold as a racemic mixture, consisting of 50% (R)-(−)-citalopram and 50% (S)-(+)-citalopram. Only the (S)-(+) enantiomer has the desired antidepressant effect.Lundbeck now markets the (S)-(+) enantiomer, the generic name of which is escitalopram. Whereas citalopram is supplied as the hydrobromide, escitalopram is sold as the oxalate salt (hydrooxalate). In both cases, the salt forms of the amine make these otherwise lipophilic compounds water-soluble.
Citalopram is metabolized in the liver mostly by CYP2C19, but also by CYP3A4 and CYP2D6. Metabolites desmethylcitalopram and didesmethylcitalopram are significantly less energetic and their contribution to the overall action of citalopram is negligible. The half-life of citalopram is about 35 hours. Approximately 80% is cleared by the liver and 20% by the kidneys. The elimination process is slower in the elderly and in patients with hepatic or renal failure. With once-daily dosing, steady plasma concentrations are achieved in about a week. Potent inhibitors of CYP2C19 and 3A4 might decrease citalopram clearance.
Tobacco smoke exposure was found to inhibit the biotransformation of citalopram in animals, suggesting that the elimination rate of citalopram is
decreased after tobacco smoke exposure. After intragastric administration, the half-life of the racemic mixture of citalopram was increased by about 287%.
Citalopram was first synthesized in 1972 by chemist Klaus Bøgesø and his research group at the pharmaceutical company Lundbeck and was first marketed in 1989 in Denmark. It was first marketed in the US in 1998. The patent expired in 2003, allowing other companies to legally produce generic versions.
On 19 June 2013, the European Commission imposed a fine of €93.8 million on the Danish pharmaceutical company Lundbeck, plus a total of €52.2 million on several generic pharmaceutical-producing companies. This was in response to Lundbeck entering an agreement with the companies to delay their sales of generic citalopram after Lundbeck's patent on the drug had expired, thus reducing competition in breach of European antitrust law.
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