What is the safest first‑line antitussive for an otherwise healthy adult with a dry cough?

Safest First-Line Antitussive for Dry Cough in Healthy Adults

Dextromethorphan at 30-60 mg per dose (maximum 120 mg daily) is the safest and most effective first-line antitussive for otherwise healthy adults with dry cough, with a superior safety profile compared to opioid alternatives. 1

Primary Recommendation: Dextromethorphan

• Dextromethorphan has no efficacy disadvantage compared to codeine but carries a much lower adverse effect profile, avoiding drowsiness, nausea, constipation, and physical dependence 1, 2
• The effective dose is 30-60 mg per dose, with maximum cough reflex suppression occurring at 60 mg 1, 3
• Standard over-the-counter formulations contain subtherapeutic doses (typically 10-15 mg) that will not provide adequate relief 1, 3
• Dextromethorphan can be dosed every 6-8 hours, with a maximum daily dose of 120 mg 4, 1

Critical Dosing Pitfall to Avoid

• Most OTC dextromethorphan products are underdosed at 10-15 mg per dose 1, 3
• When prescribing higher doses (60 mg), verify that combination products do not contain excessive acetaminophen or other ingredients that could cause toxicity 1, 3

Non-Pharmacologic First-Line Options (Before Medication)

• Honey and lemon mixtures are as effective as pharmacological treatments for benign viral cough and should be tried first 1, 3
• Menthol inhalation provides acute, short-lived cough suppression for temporary relief 1, 3
• Voluntary cough suppression techniques may sufficiently reduce cough frequency in some patients 3

For Nocturnal Cough Specifically

• First-generation sedating antihistamines (such as chlorpheniramine or diphenhydramine) suppress cough while promoting sleep 1, 3
• These are particularly suitable when cough disrupts sleep, though drowsiness is expected 1, 5
• A bedtime dose of dextromethorphan 15-30 mg can also help suppress nighttime cough 1

What NOT to Use

• Codeine-containing products are explicitly not recommended as they have no greater efficacy than dextromethorphan but significantly more adverse effects 1, 3
• The British Thoracic Society specifically recommends against codeine-based antitussives 1
• Promethazine has no established efficacy for cough suppression and carries risks of hypotension, respiratory depression, and extrapyramidal reactions 1

Practical Treatment Algorithm

1. Start with honey-lemon mixture for simple viral cough 1, 3
2. Add menthol inhalation for acute breakthrough symptoms 1, 3
3. Prescribe dextromethorphan 30-60 mg every 6-8 hours (not standard OTC doses) if non-pharmacologic measures fail 1, 3
4. For nocturnal cough, add a first-generation antihistamine at bedtime 1, 3
5. Discontinue if no improvement after 3-5 days and reassess for underlying causes 4, 1

Important Safety Considerations

• Dextromethorphan should only be used for dry, non-productive cough 1, 3
• Do not suppress productive cough where secretion clearance is beneficial 3, 6
• Cough lasting more than 3 weeks requires diagnostic workup, not continued antitussive therapy 1
• Dextromethorphan has been safely used for over 30 years with infrequent and usually non-severe adverse reactions 7

When Dextromethorphan Fails

• For postinfectious cough, try inhaled ipratropium before escalating to other agents 1, 3
• For severe paroxysms, consider prednisone 30-40 mg daily for a short course 1, 3
• Reserve opioid derivatives (preferably pholcodine, hydrocodone, or dihydrocodeine over codeine) only when non-opioid options fail 4, 1