Dextromethorphan Dosing for Asian Adults
For Asian adults, dextromethorphan should be dosed at 30-60 mg for optimal cough suppression, with 60 mg providing maximum cough reflex suppression. 1, 2
Standard Dosing Recommendations
The optimal therapeutic dose is 60 mg, which provides maximum cough reflex suppression and can be prolonged. 1, 2
Standard over-the-counter dosing (typically 15-30 mg) is often subtherapeutic and may not provide adequate relief. 1, 2
For adults, dosing of 60 mg provides superior cough suppression compared to lower doses. 1
Dextromethorphan can be dosed every 12 hours when used in combination formulations. 3
Important Pharmacogenetic Considerations for Asian Populations
While the guidelines do not specify different dosing for Asian adults specifically, Asian populations have higher rates of CYP2D6 poor metabolizer phenotype, which affects dextromethorphan metabolism. 3
In poor metabolizers, dextromethorphan plasma concentrations are significantly higher and persist longer than in extensive metabolizers. 3
Poor metabolizers achieve therapeutic levels with standard dosing without requiring CYP2D6 inhibition. 3
Given the higher prevalence of poor metabolizer status in Asian populations, starting at 30 mg and titrating to 60 mg based on response and tolerability is prudent. 1, 3
Practical Dosing Algorithm
Start with 30 mg as a single dose for initial assessment of response and tolerability. 1, 4
If inadequate response and no adverse effects, increase to 60 mg for maximum cough suppression. 1, 2
Limit duration to short-term use (typically less than 7 days). 2
Monitor for adverse effects including drowsiness, dizziness, or dissociative symptoms, which may indicate poor metabolizer status or excessive dosing. 3, 5
Safety Considerations
Dextromethorphan has a superior safety profile compared to codeine-based antitussives. 1, 2
Exercise caution with combination preparations containing other ingredients like acetaminophen when using higher doses. 1
The drug is well-tolerated even in poor metabolizers when appropriately dosed. 3
Avoid use in productive cough where secretion clearance is beneficial. 2