What is the appropriate medication and dosing for an adult with a dry (non‑productive) cough and no contraindications?

Medication for Dry Cough in Adults

For an adult with dry (non-productive) cough and no contraindications, dextromethorphan 30–60 mg every 6–8 hours (maximum 120 mg/day) is the recommended first-line pharmacological treatment, preceded by simple home remedies like honey and lemon. 1, 2

Initial Non-Pharmacological Approach

• Simple home remedies such as honey and lemon should be tried first as they are inexpensive, safe, and may be as effective as pharmacological treatments for benign viral cough. 1, 2
• Voluntary cough suppression through central modulation may be sufficient to reduce cough frequency in some patients without medication. 1, 2

First-Line Pharmacological Treatment: Dextromethorphan

Dosing Regimen

• The optimal dose for maximal cough suppression is 30–60 mg every 6–8 hours, with a maximum daily dose of 120 mg. 1
• Standard over-the-counter doses (10–15 mg) are subtherapeutic and often inadequate for meaningful cough relief. 1
• Maximum cough reflex suppression occurs at 60 mg and can be prolonged at this dose level. 1
• A bedtime dose of 15–30 mg may help suppress nocturnal cough and promote undisturbed sleep. 1

Why Dextromethorphan is Preferred

• Dextromethorphan has a superior safety profile compared to codeine-based alternatives, with no risk of physical dependence, constipation, or significant sedation. 1, 2
• It is a non-sedating centrally acting antitussive that effectively suppresses the cough reflex. 1, 2
• The American College of Chest Physicians and British Thoracic Society explicitly recommend dextromethorphan as the preferred antitussive for acute dry cough. 1

Critical Safety Considerations

• Exercise caution with combination preparations (e.g., products containing acetaminophen/paracetamol), as higher doses of dextromethorphan could lead to toxic levels of other ingredients. 1
• Check all combination products carefully to avoid excessive amounts of acetaminophen when prescribing higher doses. 1

Alternative Options for Specific Situations

For Nocturnal Cough

• First-generation sedating antihistamines (e.g., diphenhydramine, but NOT promethazine) may be used at bedtime when cough disrupts sleep, as their sedative properties help reduce cough while promoting rest. 1, 2
• Promethazine should be avoided due to serious adverse effects including hypotension, respiratory depression, and extrapyramidal reactions. 1

For Acute Breakthrough Symptoms

• Menthol inhalation (crystals or proprietary capsules) provides short-lived, acute cough suppression useful for temporary symptom relief. 1, 2
• The effect is acute but short-lived, making it suitable only for breakthrough episodes. 1

Alternative Antitussive: Benzonatate

• Benzonatate 100–200 mg three times daily (maximum 600 mg/day) is an alternative with a different mechanism of action (peripherally acting) and may be preferred when central antitussives are contraindicated. 3
• Benzonatate capsules must be swallowed whole and never broken, chewed, dissolved, cut, or crushed. 3

Medications NOT Recommended

Codeine-Based Antitussives

• Codeine and pholcodine should be avoided as they provide no greater cough suppression efficacy than dextromethorphan but have significantly more adverse effects. 1, 2
• Adverse effects include drowsiness, nausea, constipation, and risk of physical dependence. 1
• The British Thoracic Society explicitly recommends against codeine-containing antitussives for cough management. 1

Expectorants (Guaifenesin)

• Guaifenesin is NOT indicated for dry cough as it functions as an expectorant, not a cough suppressant, and does not address the therapeutic goal of cough suppression in non-productive cough. 1
• The American College of Chest Physicians assigns a Grade D recommendation (good evidence of no benefit) against mucus-altering agents for cough suppression. 1

Common Prescribing Pitfalls to Avoid

• Using subtherapeutic doses of dextromethorphan (less than 30 mg) will likely fail to provide adequate cough relief. 1
• Prescribing codeine-containing products, which lack efficacy advantage and increase side-effect burden. 1
• Failing to check combination products for additional ingredients like acetaminophen when prescribing higher doses. 1
• Using expectorants for dry cough when the goal is suppression, not secretion clearance. 1

When to Reassess or Refer

• If cough persists beyond 3 weeks, discontinue antitussive therapy and perform a full diagnostic workup to evaluate for alternative diagnoses rather than continuing symptomatic treatment. 1
• Red flags requiring immediate medical evaluation include hemoptysis, increasing breathlessness, fever with purulent sputum, or suspected foreign body inhalation. 2