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| Pronunciation | /ɡwaɪˈfɛnɪsɪn/[1] gwy-FEH-nih-seen |
| Trade names | Mucinex, others |
| Other names | Glyceryl guaiacolate |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682494 |
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| Routes of administration | By mouth |
| Drug class | Expectorant |
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| Pharmacokinetic data | |
| Metabolism | Kidney |
| Eliminationhalf-life | 1–5 hours[2] |
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| ECHA InfoCard | 100.002.021 |
| Chemical and physical data | |
| Formula | C10H14O4 |
| Molar mass | 198.218 g·mol−1 |
| 3D model (JSmol) | |
| Chirality | Racemic mixture |
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Guaifenesin, also known asglyceryl guaiacolate, sold under the brand nameMucinex, among others,[3] is anexpectorant medication taken by mouth and marketed as an aid to eliminatesputum from therespiratory tract. Chemically, it is anether ofguaiacol andglycerine. It may be used in combination with other medications.[4] A 2014 study found that guaifenesin does not affect sputum volume in upper respiratory infections (the upper respiratory system includes most breathing parts above the lungs).[5][6] It has been alleged to work in 2023[4] by making airway secretions more liquid.
Side effects may includedizziness,sleepiness,skin rash, andnausea.[4] While it has not been properly studied in pregnancy, it appears to be safe.[7]
Guaifenesin has been used medically since at least 1933.[8] It is available as ageneric medication andover-the-counter (OTC).[4][7] In 2023, it was the 291st most commonly prescribed medication in the United States, with more than 500,000 prescriptions.[9][10] In 2023, the combination dextromethorphan/guaifenesin was the 315th most commonly prescribed medication in the United States, with more than 200,000 prescriptions.[11]
Guaifenesin is used to try to help with coughing up thick mucus. It is sometimes combined with theantitussive (cough suppressant)dextromethorphan, such as in Mucinex DM or Robitussin DM.[12] It is also combined withephedrine in Primatene and Bronkaid tablets for symptomatic relief ofasthma. Guaifenesin is combined withphenylephrine andparacetamol in certainLemsip formulations.[13]
ACochrane review identified threeclinical trials assessing guaifenesin for the treatment of acute cough, with one finding significant benefit and the other two trials finding that it was not effective.[14]
Although generally well-tolerated, side effects of guaifenesin may include anallergic reaction (rare),nausea,vomiting,dizziness, orheadache.[15][16]
Guaifenesin might act as an expectorant by increasing the volume and reducing the viscosity of secretions in thetrachea andbronchi via stimulation of the gastric mucosa. This stimulation leads to an increased parasympathetic activity in the respiratory tract via the so-called gastro-pulmonary reflex, although some in vitro studies suggested that it might also act directly on the respiratory epithelium.[17] This increase in volume and reduction in viscosity aids in the flow of respiratory tract secretions, allowing ciliary movement to carry the loosened secretions upward toward thepharynx.[18][19] Thus, guaifenesin may increase the efficiency of thecough reflex and facilitate the removal of the secretions. Additionally, guaifenesin has a demonstrated central antitussive effect.[20]
Similar medicines derived from theguaiac tree were used as a generic remedy by American indigenous peoples when explorers reachedNorth America in the 16th century. The Spanish encountered guaiacum wood "when they conqueredSanto 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..."[21]
The 1955 edition of theTextbook ofPharmacognosy 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 ofsarsaparilla, which was formerly much used as an alterative in syphilis."[21]
In the US, guaifenesin was first approved by theFood and Drug Administration (FDA) in 1952. Although previously deemed "Generally Regarded as Safe" in its original approval, the drug received aNew Drug Application for the extended-release version, which received approval on 12 July 2002.[22] Because of this, the FDA then issued letters to other manufacturers oftimed-release guaifenesin to stop marketing their unapproved versions, leaving Adams Respiratory Therapeutics in control of the market. In 2007, Adams was acquired byReckitt Benckiser.[23][24] The drug is now sold over-the-counter by many companies, alone and in combination.[25]
Guaifenesin's neurological properties first became known in the late 1940s. Guaifenesin is a centrally actingmuscle relaxant used routinely in large-animal veterinary surgery. Guaifenesin is used in combination with, for example,ketamine, since guaifenesin does not provide analgesia or produce unconsciousness.[26][27] In horses, the drug's biological half-life is 77 minutes. Premedication withxylazine (1.1 mg/kg) can reduce the dose required from 163 mg/kg (in geldings) to just 88 mg/kg.[27]
Guaifenesin istaken by mouth,[4] and is supplied as a tablet, a capsule, an extended-release (long-acting) tablet, dissolving granules, and a syrup.[16] It is available under manybrand names, as either the soleactive ingredient or part of acombination drug.[16] Drugs combined with guaifenesin in over-the-counter preparations include the cough-suppressantdextromethorphan,analgesics such asparacetamol/acetaminophen, anddecongestants such asephedrine,pseudoephedrine, orphenylephrine.[16]
In 2014, sales of guaifenesin were estimated to be approximately $135 million per year in the United States.[6]
