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Clinical data
Trade namesMucinex, others
Other namesGlyceryl guaiacolate
License data
Routes of
By mouth
ATC code
Legal status
Legal status
Pharmacokinetic data
Elimination half-life1–5 hours[3]
  • (RS)-3-(2-methoxyphenoxy)propane-1,2-diol
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.002.021 Edit this at Wikidata
Chemical and physical data
Molar mass198.218 g·mol−1
3D model (JSmol)
ChiralityRacemic mixture
  • O(c1ccccc1OC)CC(O)CO
  • InChI=1S/C10H14O4/c1-13-9-4-2-3-5-10(9)14-7-8(12)6-11/h2-5,8,11-12H,6-7H2,1H3 checkY

Guaifenesin, also known as glyceryl guaiacolate, is an expectorant medication taken by mouth and marketed as an aid to eliminate sputum from the respiratory tract. Chemically, it is an ether of guaiacol and glycerine. It may be used in combination with other medications.[4] A 2014 study found that guaifenesin has no effect on sputum production or clearance in upper respiratory infections.[5][6]

Side effects may include dizziness, sleepiness, skin rash, and nausea.[4] While it has not been properly studied in pregnancy, it appears to be safe.[7] It is believed to work by making airway secretions more liquid.[4]

Guaifenesin has been used medically since at least 1933.[8] It is available as a generic medication and over the counter.[4][7] In 2021, it was the 288th most commonly prescribed medication in the United States, with more than 600,000 prescriptions.[9][10]

Medical use[edit]

Guaifenesin is used to try to help with coughing up thick mucus, and is sometimes combined with the antitussive (cough suppressant) dextromethorphan, such as in Mucinex DM or Robitussin DM.[11] It is also combined with ephedrine in Primatene and Bronkaid tablets for symptomatic relief of asthma.

A Cochrane review identified only three clinical 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.[12]

Side effects[edit]

Although generally well-tolerated, side-effects of guaifenesin may include an allergic reaction (rare), nausea, vomiting, dizziness or headache.[13][14]


Mechanism of action[edit]

Guaifenesin is thought to act as an expectorant by increasing the volume and reducing the viscosity of secretions in the trachea and bronchi. It may aid in the flow of respiratory tract secretions, allowing ciliary movement to carry the loosened secretions upward toward the pharynx.[15] 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..."[16]

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."[16]

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 received approval on 12 July 2002.[17] 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. In 2007, Adams was acquired by Reckitt Benckiser.[18][19] The drug is now sold over-the-counter by many companies, alone and in combination.[20]

Society and culture[edit]

Brand names[edit]

Guaifenesin is taken by mouth,[4] and is supplied as a tablet, a capsule, an extended-release (long-acting) tablet, dissolving granules, and a syrup.[14] It is available under many brand names, as either the sole active ingredient or part of a combination drug.[14] Drugs combined with guaifenesin in over-the-counter preparations include the cough-suppressant dextromethorphan, analgesics such as paracetamol/acetaminophen, and decongestants such as ephedrine, pseudoephedrine, or phenylephrine.[14]


In 2014, sales of guaifenesin were estimated to be approximately $135 million per year in the United States.[6]

Veterinary use[edit]

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 provide analgesia or produce unconsciousness.[21][22]


  1. ^ "Guaifenesin Definition & Meaning". Merriam-Webster.
  2. ^ "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". nctr-crs.fda.gov. FDA. Retrieved 22 October 2023.
  3. ^ Aluri JB, Stavchansky S (1993). "Determination of guaifenesin in human plasma by liquid chromatography in the presence of pseudoephedrine". J Pharm Biomed Anal. 11 (9): 803–808. doi:10.1016/0731-7085(93)80072-9. PMID 8218524.
  4. ^ a b c d e "Guaifenesin: Monograph for Professionals". Drugs.com, American Society of Health-System Pharmacists. 23 January 2023. Retrieved 30 July 2023.
  5. ^ Hoffer-Schaefer A, Rozycki HJ, Yopp MA, Rubin BK (May 2014). "Guaifenesin has no effect on sputum volume or sputum properties in adolescents and adults with acute respiratory tract infections". Respiratory Care. 59 (5): 631–636. doi:10.4187/respcare.02640. PMID 24003241.
  6. ^ a b O'Connell OJ (May 2014). "Is extended-release guaifenesin no better than a placebo?". Respir Care. 59 (5): 788–9. doi:10.4187/respcare.03319. PMID 24789023.
  7. ^ a b Weiner CP, Rope K (2013). The Complete Guide to Medications During Pregnancy and Breastfeeding: Everything You Need to Know to Make the Best Choices for You and Your Baby. St. Martin's Press. p. PT282. ISBN 9781250037206.
  8. ^ Riviere JE, Papich MG (2013). Veterinary Pharmacology and Therapeutics. John Wiley & Sons. p. 287. ISBN 9781118685907.
  9. ^ "The Top 300 of 2021". ClinCalc. Archived from the original on 15 January 2024. Retrieved 14 January 2024.
  10. ^ "Guaifenesin – Drug Usage Statistics". ClinCalc. Retrieved 14 January 2024.
  11. ^ "Guaifenesin DM". WebMD.com.
  12. ^ Smith SM, Schroeder K, Fahey T (November 2014). "Over-the-counter (OTC) medications for acute cough in children and adults in community settings". Cochrane Database Syst Rev. 2014 (11): CD001831. doi:10.1002/14651858.CD001831.pub5. PMC 7061814. PMID 25420096.
  13. ^ "Guaifenesin Side Effects". Drugs.com. 3 July 2023. Retrieved 30 July 2023.
  14. ^ a b c d "Guaifenesin". MedlinePlus, United States National Library of Medicine. 15 January 2022. Retrieved 30 July 2023.
  15. ^ Gutierrez, K. (2007). Pharmacotherapeutics: Clinical Reasoning in Primary Care. W.B. Saunders Co.
  16. ^ a b Wallis TE (1955). Textbook of Pharmacognosy.
  17. ^ "Drug Approval Package: Mucinex (Guaifenesin) NDA #21-282". accessdata.fda.gov. 25 November 2002. Retrieved 26 October 2022.
  18. ^ "Announcements RB Press release - 10/12/2007". Archived from the original on 15 July 2011. Retrieved 16 November 2010.
  19. ^ Goldstein J (25 May 2007). "FDA Bumps Phlegm-Fighters From Market". The Wall Street Journal. Retrieved 16 November 2010.
  20. ^ "Guaifenesin (Oral Route) Description and Brand Names". Mayo Clinic. Retrieved 27 July 2021.
  21. ^ Tranquilli WJ, Thurmon JC, Grimm KA, eds. (2007). "Centrally Acting Muscle Relaxants". Lumb and Jones' Veterinary Anesthesia and Analgesia (2nd ed.). Blackwell Publishing.
  22. ^ Valverde A (April 2013). "Balanced anesthesia and constant-rate infusions in horses". Vet Clin North Am Equine Pract. 29 (1): 89–122. doi:10.1016/j.cveq.2012.11.004. PMID 23498047.

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