What is the recommended dosing for Robitussin (Guaifenesin) in a typical adult patient?

Robitussin (Guaifenesin) Dosing for Adults

For typical adults, the recommended dose of guaifenesin is 200-400 mg every 4 hours (not exceeding 2400 mg per day), or 600-1200 mg every 12 hours if using extended-release formulations. 1

Standard Immediate-Release Dosing

• Adults and children ≥12 years: 10-20 mL (200-400 mg) every 4 hours 1
• Maximum: Do not exceed 6 doses in 24 hours (2400 mg total daily dose) 1
• The flexible dosing range of 200-400 mg allows titration based on symptom severity and individual response 2

Extended-Release Formulations

• Dosing: 600 mg or 1200 mg every 12 hours 3
• Extended-release tablets provide equivalent steady-state exposure to immediate-release formulations dosed every 4 hours, offering more convenient twice-daily dosing 3
• The 1200 mg extended-release dose can be taken with or without food, though food delays time to peak concentration without affecting overall absorption 3

Clinical Context and Efficacy

Guaifenesin works as an expectorant by loosening mucus and making coughs more productive, with established use for wet cough and chest congestion from upper respiratory tract infections 2. The drug has demonstrated:

• Reduction in sputum thickness in 96% of patients with productive cough (compared to 54% with placebo) 4
• Decreased sputum quantity in 88% of guaifenesin-treated patients versus 62.5% receiving placebo 4
• Inhibition of cough reflex sensitivity in patients with acute viral upper respiratory infections, though not in healthy volunteers 5

Important Considerations

• Multiple daily doses are required with immediate-release formulations to maintain 24-hour therapeutic effect due to guaifenesin's short half-life 2, 3
• The drug is most effective for mucus-related symptoms in acute upper respiratory tract infections and stable chronic bronchitis 2
• Guaifenesin has a well-established safety profile in both adult and pediatric populations 2
• No antitussive effect on cough frequency has been objectively demonstrated, though subjective improvements in sputum characteristics are reported 4