Generic Dextromethorphan: Formulation and Dosage
The generic version of Robitussin is dextromethorphan, available as dextromethorphan hydrobromide or dextromethorphan polistirex, with standard adult dosing of 10-30 mg every 4-8 hours, not exceeding 120 mg in 24 hours.
Dextromethorphan Formulations
Dextromethorphan is available in several formulations:
Immediate-release (dextromethorphan hydrobromide):
- Tablets/capsules: 15-30 mg
- Liquid/syrup: 7.5-15 mg/5 mL
- Lozenges: 5-15 mg
Extended-release (dextromethorphan polistirex):
- Liquid: 30 mg/5 mL (equivalent to dextromethorphan hydrobromide)
Standard Dosing Guidelines
For immediate-release formulations:
- Adults and children ≥12 years: 10-30 mg every 4-6 hours, not to exceed 120 mg in 24 hours 1
- Children 6-12 years: 5-10 mg every 4 hours or 15 mg every 6-8 hours, not to exceed 60 mg in 24 hours
- Children 4-6 years: 2.5-5 mg every 4 hours or 7.5 mg every 6-8 hours, not to exceed 30 mg in 24 hours
- Children <4 years: Not recommended
For extended-release formulations (polistirex) 2:
- Adults and children ≥12 years: 10 mL (30 mg) every 12 hours, not to exceed 20 mL in 24 hours
- Children 6-12 years: 5 mL (15 mg) every 12 hours, not to exceed 10 mL in 24 hours
- Children 4-6 years: 2.5 mL (7.5 mg) every 12 hours, not to exceed 5 mL in 24 hours
- Children <4 years: Not recommended
Clinical Efficacy and Considerations
Dextromethorphan has been shown to suppress cough in chronic bronchitis by 40-60%, but has limited efficacy (<20% suppression) in cough due to upper respiratory infections 1
Maximum cough reflex suppression occurs at 60 mg and can be prolonged, though most OTC preparations contain lower doses 1
Dextromethorphan is generally preferred over codeine for cough suppression due to:
- Similar efficacy at standard doses 3
- Better safety profile with fewer side effects
- Non-narcotic status
- Lower abuse potential at therapeutic doses
Important Precautions
Avoid high doses: Consumption exceeding 1500 mg/day can induce psychosis with hallucinations, delusions, and paranoia 4
Drug interactions: Use caution when combining with:
- Probenecid (increases dextromethorphan levels)
- Serotonergic medications (risk of serotonin syndrome) 5
- MAO inhibitors (contraindicated)
Measurement: Always use the provided dosing cup or measuring device for liquid formulations 2
Duration of use: For short-term symptomatic relief only; reassess if symptoms persist beyond 7 days
Dextromethorphan is widely available as a generic medication in various OTC cough and cold preparations, making it an accessible and generally safe option for temporary cough suppression when used as directed.