Guaifenesin has no effect on sputum volume or sputum properties in adolescents and adults with acute respiratory tract infections

Respir Care. 2014 May;59(5):631-6. doi: 10.4187/respcare.02640. Epub 2013 Sep 3.


Background: Guaifenesin (glyceryl guaiacolate ether [GGE]) has been studied as a cough suppressant and as an expectorant; however, published studies to date have failed to find a consistent benefit.

Methods: An 8-day multi-center clinical trial was conducted to study the effect of two 600-mg extended-release GGE tablets twice daily for 1 week on cold symptoms, sputum volume, and properties in adolescents and adults with productive cough from an acute respiratory tract infection (RTI). The study enrolled 378 subjects (GGE, n = 188; and placebo, n = 190) who were otherwise healthy and had an RTI for up to 5 days before enrollment. Subjects suffered from at least 2 of 3 symptoms of cough, thickened mucus, and chest congestion. A total of 151 GGE and 144 control subjects completed the full protocol. Single-sputum samples were collected from each subject on days 1, 3, 4, and 8 of the study. The rheology and interfacial tension of sputum were measured, and 24-h collected samples from days 1 and 4 were analyzed for total volume and hydration.

Results: Symptoms in both the GGE and placebo groups improved to a similar degree over time. There were no significant differences between the GGE and placebo groups for sputum volume (P = .41), percent solids (P = .69), interfacial tension (P = .88), elasticity (P = .71), viscosity (P = .45), or mechanical impedance (P = .75).

Conclusions: The recommended dose of GGE had no measurable effect on sputum volume or properties and is unlikely to be an expectorant or mucolytic when used to treat acute RTI. ( registration NCT01046136.).

Keywords: cough therapy; expectorant; guaifenesin; mucus; upper respiratory infection.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Double-Blind Method
  • Elasticity / drug effects
  • Expectorants / pharmacology*
  • Female
  • Guaifenesin / pharmacology*
  • Humans
  • Male
  • Middle Aged
  • Mucus / chemistry
  • Mucus / drug effects
  • Respiratory Tract Infections / complications
  • Respiratory Tract Infections / drug therapy*
  • Rheology / drug effects
  • Sputum / drug effects*
  • Surface Tension / drug effects
  • Viscosity / drug effects
  • Water / analysis
  • Young Adult


  • Expectorants
  • Water
  • Guaifenesin

Associated data