|Trade names||Mucinex, others|
|By mouth (tablets, syrup)|
|Elimination half-life||1–5 hours|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||198.216 g/mol g·mol−1|
|3D model (JSmol)|
Guaifenesin, sold under the brand name Mucinex among others, is a medication used to try to help cough out phlegm from the airways. It is unclear if it decreases coughing. Use is not recommended in children less than 6 years old. It is often used in combination with other medications. It is taken by mouth.
Side effects may include dizziness, sleepiness, skin rash, and nausea. While it has not been properly studied in pregnancy, it appears to be safe. It is believed to work by making airway secretions more liquid.
Guaifenesin has been used medically since at least 1933. It is available as a generic medication and over the counter. In the United States the wholesale cost is less than 0.10 USD per dose. In 2016 it was the 261st most prescribed medication in the United States with more than a million prescriptions.
Guaifenesin is used to try to help with coughing up thick mucous and is sometimes combined with dextromethorphan, an antitussive (cough medicine), such as in Mucinex DM or Robitussin DM. It is also combined with ephedrine to produce Primatene and Bronkaid tablets for symptomatic relief of asthma.
Side-effects of guaifenesin include nausea, vomiting, formation of kidney stones, diarrhea, and constipation. Nausea and vomiting can be reduced by taking guaifenesin with meals. The risk of forming kidney stones during prolonged use can be reduced by maintaining good hydration and increasing the pH of urine. Rarely, severe allergic reactions may occur, including a rash or swelling of the lips or gums, which may require urgent medical assistance. Mild dry mouth or chapped lips may also occur when taking this medication. Drinking a glass of water is recommended with each dose of guaifenesin.
Guaifenesin increases the analgesic effect of paracetamol (acetaminophen) and aspirin, increases the sedative effects of alcohol, tranquilisers, sleep-pills and total anesthetics.[medical citation needed]
Guaifenesin is thought to act as an expectorant by increasing the volume and reducing the viscosity of secretions in the trachea and bronchi. It has been said to aid in the flow of respiratory tract secretions, allowing ciliary movement to carry the loosened secretions upward toward the pharynx. Thus, it may increase the efficiency of the cough reflex and facilitate removal of the secretions.
Similar medicines derived from the guaiac tree were in use as a generic remedy by American indigenous peoples when explorers reached North America in the 16th century. The Spanish encountered guaiacum wood "when they conquered Santo Domingo; it was soon brought back to Europe, where it acquired an immense reputation in the sixteenth century as a cure for syphilis and certain other diseases..."
The 1955 edition of the Textbook of Pharmacognosy states: "Guaiacum has a local stimulant action which is sometimes useful in sore throat. The resin is used in chronic gout and rheumatism, whilst the wood is an ingredient in the compound concentrated solution of sarsaparilla, which was formerly much used as an alternative in syphilis."
In the US, Guaifenesin was first approved by the Food and Drug Administration (FDA) in 1952. Although previously deemed "Generally Regarded as Safe" in its original approval, the drug received a New Drug Application for the extended-release version, which won approval on July 12, 2002. Because of this, the FDA then issued letters to other manufacturers of timed-release guaifenesin to stop marketing their unapproved versions, leaving Adams Respiratory Therapeutics in control of the market. Adams was subsequently acquired by Reckitt Benckiser, based on the strength of the marketing generated by Adams' Mucinex brand.
Guaifenesin is sold as pills or syrups under many brand names. Single-ingredient formulations of guaifenesin are available, and it is also included in many other over-the-counter cough and cold remedy combinations (usually in conjunction with dextromethorphan, paracetamol (acetaminophen), ephedrine, pseudoephedrine, or phenylephrine).
Guaifenesin's neurological properties first became known in the late 1940s. Guaifenesin is a centrally acting muscle relaxant used routinely in large-animal veterinary surgery. Guaifenesin is used in combination with, for example, ketamine, since guaifenesin does not produce analgesia nor does it produce unconsciousness.
The guaifenesin protocol was studied as a method to treat fibromyalgia; a one-year double-blind study found that the treatment performs no better than placebo. Guaifenesin is not approved by the FDA for the treatment of fibromyalgia.
Guaifenesin was studied as a method to improve the possibility of conception, by thinning and increasing the stretchability (improved spinnbarkeit) of the cervical mucus, during the few days before ovulation, thus facilitating sperm penetration.