Recommended Concentration of Dextromethorphan
The standard concentration of dextromethorphan (DM) in liquid formulations is 6 mg/mL (30 mg per 5 mL) as indicated in the FDA drug label for dextromethorphan polistirex syrup. 1
Dosage Guidelines
Dextromethorphan is commonly available in the following concentrations:
- Standard liquid formulation: 6 mg/mL (30 mg per 5 mL)
- For pediatric use, the dosing is typically age-based rather than strictly weight-based:
Weight-Based Dosing Considerations
While age-based dosing is common in clinical practice, research suggests that weight-based dosing may provide more consistent therapeutic effects:
- Optimal weight-based dosing appears to be around 0.5 mg/kg per dose
- Dose ranges studied in research:
- Low dose: 0.35 to <0.45 mg/kg
- Medium dose: 0.45 to <0.60 mg/kg
- High dose: 0.60-0.94 mg/kg 3
The medium dose range (0.45-0.60 mg/kg) may offer the best balance between efficacy and minimizing adverse effects, as higher doses were associated with more side effects in clinical studies. 3
Clinical Application
When using dextromethorphan for cough suppression:
- Use for dry, non-productive cough that is bothersome and disruptive
- Avoid use when the patient is coughing up significant amounts of sputum
- Standard adult dosing is 10-15 mg three to four times daily 2
- Efficacy for cough suppression is modest (less than 20% suppression) 2, 4
Important Considerations
- Dextromethorphan has a relatively short half-life, requiring multiple daily doses for sustained effect 5, 6
- Metabolism varies based on CYP2D6 genetic status, with poor metabolizers potentially experiencing higher blood levels and increased risk of side effects 5
- Abuse potential exists, particularly in adolescents and young adults, with recreational doses far exceeding therapeutic recommendations 6
For clinical practice, the standard 6 mg/mL (30 mg per 5 mL) concentration provides a practical formulation that allows appropriate dosing across age groups while maintaining a reasonable volume for administration.