What is the maximum daily dose of Geri-Tussin (dextromethorphan)?

Maximum Daily Dose of Geri-Tussin (Dextromethorphan)

The maximum daily dose of dextromethorphan for adults is 120 mg per day, typically administered as 10-15 mg three to four times daily, or as extended-release formulations of 60 mg every 12 hours (not exceeding 120 mg in 24 hours). 1, 2

FDA-Approved Dosing by Age

The FDA labeling for dextromethorphan products provides clear maximum daily doses based on age groups 2:

• Adults and children ≥12 years: 10 mL every 12 hours, not to exceed 20 mL (equivalent to 60 mg per dose, 120 mg per 24 hours) 2
• Children 6 to <12 years: 5 mL every 12 hours, not to exceed 10 mL in 24 hours 2
• Children 4 to <6 years: 2.5 mL every 12 hours, not to exceed 5 mL in 24 hours 2
• Children <4 years: Do not use 2

Clinical Guideline Recommendations

The American College of Chest Physicians recommends dextromethorphan dosing at 10-15 mg three to four times daily, with a maximum daily dose of 120 mg for effective cough suppression 1. This aligns with the FDA labeling and represents the standard therapeutic approach.

Important Dosing Considerations

Standard OTC Dosing May Be Subtherapeutic

Standard over-the-counter dosing of dextromethorphan is often subtherapeutic for optimal cough suppression. 1 Maximum cough reflex suppression occurs at 60 mg single doses, which is higher than typical OTC recommendations 1. However, the total daily dose should still not exceed 120 mg 1.

Combination Product Warning

When prescribing or recommending higher doses of dextromethorphan, always check combination products carefully to avoid excessive amounts of other ingredients like acetaminophen. 1 Many OTC preparations combine dextromethorphan with pain relievers, decongestants, or antihistamines, which can lead to inadvertent overdose of these additional ingredients when attempting to achieve therapeutic dextromethorphan levels.

Practical Dosing Algorithm

For adults requiring cough suppression 1:

1. Start with standard dosing: 10-15 mg three to four times daily (total 40-60 mg/day)
2. If inadequate response: Consider 30 mg every 12 hours (total 60 mg/day)
3. For maximum suppression: 60 mg every 12 hours (total 120 mg/day maximum)
4. Never exceed: 120 mg in 24 hours under any circumstances

Common Pitfalls to Avoid

• Using subtherapeutic doses: Many patients receive 15-30 mg total daily, which provides minimal benefit 1
• Exceeding maximum daily dose: The 120 mg/24-hour limit must be strictly observed 1, 2
• Overlooking combination products: Patients may inadvertently exceed safe limits of acetaminophen or other ingredients when taking multiple combination products 1
• Prolonged use without reassessment: Dextromethorphan should be used for short-term symptomatic relief only; cough lasting more than 3 weeks requires full diagnostic workup 1

When Dextromethorphan Fails

If no improvement occurs after a short course at appropriate doses 1:

• Discontinue dextromethorphan and try alternative approaches
• Consider peripherally-acting antitussives like levodropropizine or moguisteine for opioid-resistant cough
• For refractory cases, nebulized lidocaine may be considered as a last resort