Dextromethorphan-Guaifenesin Combination Strengths
For adults and children 12 years and over, dextromethorphan-guaifenesin combinations typically come in formulations containing dextromethorphan 10-20 mg with guaifenesin 100-400 mg per dose, administered every 4-12 hours depending on the specific product formulation. 1, 2
Standard Dosing by Age Group
Adults and Children ≥12 Years
- Dextromethorphan: 10-20 mL (containing approximately 10-30 mg) every 4-12 hours, not exceeding 120 mg in 24 hours 3, 2
- Guaifenesin: 10-20 mL (200-400 mg) every 4 hours, not exceeding 6 doses in 24 hours 1
Children 6 to <12 Years
- Dextromethorphan: 5 mL every 12 hours, not exceeding 10 mL in 24 hours 2
- Guaifenesin: 5-10 mL (100-200 mg) every 4 hours 1
Children 4 to <6 Years
- Dextromethorphan: 2.5 mL every 12 hours, not exceeding 5 mL in 24 hours 2
- Guaifenesin: 2.5-5 mL (50-100 mg) every 4 hours 1
Children <4 Years
Important Clinical Considerations
Therapeutic Dosing Pitfalls
- Standard over-the-counter dextromethorphan dosing is often subtherapeutic - maximum cough reflex suppression occurs at 60 mg, which is higher than typical OTC recommendations 3, 4
- The American College of Chest Physicians recommends dextromethorphan 10-15 mg three to four times daily, with a maximum daily dose of 120 mg for effective cough suppression 3
- For optimal acute cough suppression in adults, consider 30-60 mg doses rather than the lower OTC strengths 3, 4
Safety Warnings with Combination Products
- Exercise caution with higher doses of dextromethorphan in combination products, as they often contain additional ingredients like acetaminophen, guaifenesin, or antihistamines that can reach toxic levels 3, 5
- Combination products containing guaifenesin with dextromethorphan add expectorant effects but increase the risk of additive toxicity in overdose 5, 6
- Always verify the complete ingredient list before recommending higher therapeutic doses 3