Safe Dosage and Usage of Dextromethorphan for Cough Suppression
Dextromethorphan is recommended as a first-line antitussive agent for non-productive cough at a dose of 60 mg for optimal cough suppression in adults, which is higher than typical over-the-counter doses. 1, 2
Recommended Dosages by Age
- Adults and children 12 years and over: 10 mL (typically 30 mg) every 12 hours, not exceeding 20 mL in 24 hours per FDA labeling, though clinical evidence suggests 60 mg provides optimal cough suppression 3, 1
- Children 6 to under 12 years: 5 mL every 12 hours, not exceeding 10 mL in 24 hours 3
- Children 4 to under 6 years: 2.5 mL every 12 hours, not exceeding 5 mL in 24 hours 3
- Children under 4 years: Not recommended 3
Clinical Efficacy
- Dextromethorphan has been shown to reduce cough frequency by 19-36% in adults with upper respiratory infections at standard doses 1
- Maximum cough reflex suppression occurs at 60 mg doses, which is higher than typically recommended in over-the-counter preparations 1, 2
- Standard over-the-counter dosing (typically 15-30 mg) is often subtherapeutic for optimal cough suppression 1, 2
- Dextromethorphan has a superior safety profile compared to opioid alternatives like codeine 1, 2
- In children aged 6-11 years, dextromethorphan has been shown to reduce total coughs over 24 hours by 21.0% and daytime cough frequency by 25.5% compared to placebo 4
Appropriate Use Cases
- Recommended for short-term symptomatic relief of non-productive cough 5, 1
- Particularly effective for cough due to chronic bronchitis, suppressing cough counts by 40-60% 5
- Should be considered only when other measures fail for postinfectious cough 1
- Not recommended for productive cough where clearance of secretions is beneficial 1, 6
Treatment Alternatives and Adjuncts
- Simple home remedies like honey and lemon may be as effective as pharmacological treatments and should be considered first for benign viral cough 1, 2
- Menthol by inhalation provides acute but short-lived cough suppression 1
- First-generation sedative antihistamines can suppress cough and are particularly suitable for nocturnal cough 1, 2
- For postinfectious cough, inhaled ipratropium may be tried before central antitussives 1, 2
Safety Considerations and Precautions
- Duration of treatment should be limited to short-term use (typically less than 7 days) 2
- Caution with higher doses of dextromethorphan as some combined preparations contain other ingredients like paracetamol 1
- At inappropriately high doses (over 1500 mg/day), dextromethorphan can induce psychosis characterized by delusions, hallucinations, and paranoia 7
- The combination of dextromethorphan/quinidina should be used with caution in older adults due to increased risk of falls and drug interactions 6
Evidence Quality and Contradictions
- Evidence for dextromethorphan efficacy is mixed, with some studies showing significant benefits while others show minimal effects 1, 8
- A 1983 study found that both dextromethorphan and codeine at 20 mg doses were similarly effective in reducing cough frequency, but dextromethorphan lowered cough intensity to a greater degree 9
- A 2000 study found little support for clinically significant antitussive activity of a single 30 mg dose in patients with cough associated with acute upper respiratory tract infection 8
- The American College of Chest Physicians guidelines note that not all suppressant drugs are effective, especially in cough due to upper respiratory infections 5