What is the recommended dosage of guaifenesin (expectorant) for treating a cough?

Guaifenesin Dosing for Cough

The recommended dosage of guaifenesin for cough is 200-400 mg every 4 hours (up to 6 times daily, maximum 2400 mg/24 hours) for immediate-release formulations, or 600-1200 mg every 12 hours for extended-release formulations. 1, 2

Standard Dosing Regimens

Immediate-Release Formulations

• 200-400 mg every 4 hours is the standard dosing range, allowing flexible dose titration based on symptom severity 2
• Maximum of 6 doses per 24 hours (total daily maximum: 2400 mg) 2
• Multiple daily doses are necessary to maintain therapeutic effect throughout the day due to guaifenesin's short half-life 2, 3

Extended-Release Formulations

• 600 mg every 12 hours for moderate symptoms 3
• 1200 mg every 12 hours for more severe mucus-related symptoms 1, 3
• Extended-release tablets provide convenience with twice-daily dosing and are bioequivalent to corresponding immediate-release doses 3
• Food delays time to peak concentration (Tmax) but does not affect overall exposure, so can be taken with or without food 3

Duration of Treatment

• Short-term use only (typically 5-7 days) is recommended 1
• Reassess if symptoms persist beyond one week, as prolonged cough may indicate an underlying condition requiring different management 1

Clinical Context and Mechanism

Guaifenesin works as an expectorant by increasing airway water content and reducing mucus viscosity, thereby promoting effective cough and mucociliary clearance 2, 4. The drug has demonstrated efficacy specifically in:

• Acute upper respiratory tract infections (URTIs) with productive cough 2, 4
• Stable chronic bronchitis where mucus hypersecretion is prevalent 2
• Studies show guaifenesin inhibits cough reflex sensitivity in patients with URI (whose cough receptors are transiently hypersensitive) but not in healthy volunteers 4

Important Clinical Considerations

Safety Profile

• Well-tolerated with minimal side effects at recommended doses in both adult and pediatric populations 2
• Generally safe for use without significant drug interactions at therapeutic doses 1

When to Avoid or Use Caution

• Do not use in chronic bronchitis with significant sputum retention where cough suppression could be harmful 1
• Avoid combining with codeine or other cough suppressants in conditions like bronchiectasis where effective cough clearance is essential 1

Combination Therapy

• When combined with benzonatate, guaifenesin shows potentiated antitussive effects greater than either agent alone 5
• The combination of guaifenesin 600 mg with benzonatate 200 mg demonstrated superior cough suppression compared to either drug individually 5

Common Pitfalls to Avoid

• Underdosing: The 200 mg dose may be subtherapeutic for many patients; consider starting at 400 mg every 4 hours for immediate-release formulations 2
• Expecting immediate results: Guaifenesin requires consistent dosing to maintain therapeutic plasma concentrations throughout the day 3
• Using in dry, non-productive cough: Guaifenesin is indicated for wet cough with mucus production, not dry cough where antitussives may be more appropriate 2
• Prolonged use without reassessment: Cough persisting beyond 7 days warrants evaluation for underlying causes rather than continued symptomatic treatment 1