Dextromethorphan Dosing in Milliliters
For adults and children 12 years and older, administer 10 mL every 12 hours; for children 6 to under 12 years, give 5 mL every 12 hours; for children 4 to under 6 years, give 2.5 mL every 12 hours. 1
Age-Based Dosing Algorithm
The FDA-approved dosing for standard dextromethorphan extended-release oral suspension (containing 30 mg dextromethorphan hydrobromide per 5 mL) is straightforward 1:
Specific Volumes by Age:
Adults and children ≥12 years: 10 mL every 12 hours
- Maximum: 20 mL in 24 hours
Children 6 to <12 years: 5 mL every 12 hours
- Maximum: 10 mL in 24 hours
Children 4 to <6 years: 2.5 mL every 12 hours
- Maximum: 5 mL in 24 hours
Children <4 years: Do not use 1
Critical Administration Points
Always shake the bottle well before use and measure only with the dosing cup provided with the product. Do not use the dosing cup with other products, as concentration varies between formulations 1.
Evidence Context
While the 2006 ACCP guidelines show mixed evidence for dextromethorphan's efficacy in cough suppression—with some studies showing benefit at 30-60 mg doses and others showing no significant effect 2—the FDA-approved dosing remains the standard for clinical practice. The guideline evidence demonstrates that dextromethorphan at 60 mg reduced cough counts by 50% in chronic bronchitis patients, while 30 mg showed variable results 2.
Important Caveats
- The extended-release formulation (polistirex) provides 12-hour coverage, which differs from immediate-release formulations that may require more frequent dosing
- This dosing applies specifically to the extended-release oral suspension formulation 1
- Patients with CYP2D6 polymorphisms (approximately 6% of Black Americans and 5-10% of white populations) may have altered metabolism, though standard dosing typically remains appropriate 3