Fenesin Side Effects
Generic name: guaifenesin
Medically reviewed by Drugs.com. Last updated on Aug 22, 2022.
Note: This document contains side effect information about guaifenesin. Some dosage forms listed on this page may not apply to the brand name Fenesin.
Applies to guaifenesin: oral liquid, oral solution, oral syrup, oral tablet, oral tablet extended release.
Serious side effects of Fenesin
Along with its needed effects, guaifenesin (the active ingredient contained in Fenesin) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Other side effects of Fenesin
Some side effects of guaifenesin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Less common or rare
For Healthcare Professionals
Applies to guaifenesin: compounding powder, oral capsule, oral capsule extended release, oral granule, oral liquid, oral solution, oral tablet, oral tablet extended release.
Guaifenesin (the active ingredient contained in Fenesin) has been generally well tolerated.[Ref]
Gastrointestinal side effects have included stomach upset and vomiting with higher than recommended doses. Doses recommended for expectoration have rarely been associated with gastrointestinal upset.[Ref]
Nervous system side effects have occasionally included dizziness and headache.[Ref]
Dermatologic side effects have included rare reports of rash.[Ref]
Frequently asked questions
More about Fenesin (guaifenesin)
Related treatment guides
1. Covington TR, eds., Lawson LC, Young LL "Handbook of Nonprescription Drugs." Washington, DC: American Pharmaceutical Association (1993):
2. "Product Information. Robitussin (guaifenesin)." Wyeth-Ayerst Laboratories (2001):
3. Manujendra R, Faltay B, Haller NA "Case report: anaphylactic reaction to guaifenesin." Hosp Pract 37 (2009): 60-3
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Some side effects may not be reported. You may report them to the FDA.