What is the first-line prescription medication for an adult with a cough?

First-Line Prescription Medication for Adult Cough

For acute cough in adults, dextromethorphan at 30-60 mg is the recommended first-line prescription antitussive, though simple home remedies like honey and lemon should be tried first as they are equally effective for benign viral cough. 1, 2

Initial Assessment and Non-Pharmacological Approach

Before prescribing any medication, rule out serious conditions requiring specific treatment:

• Red flags requiring immediate evaluation: increasing breathlessness (assess for asthma/anaphylaxis), fever with purulent sputum (possible pneumonia), significant hemoptysis, or suspected foreign body 1
• Pneumonia must be excluded first if patient has tachycardia, tachypnea, fever, or abnormal chest examination findings before using any antitussive 1

Start with simple home remedies as first-line treatment:

• Honey and lemon are the simplest, cheapest, and often as effective as pharmacological treatments for benign viral cough 1, 2
• Voluntary cough suppression through central modulation may be sufficient to reduce cough frequency 1, 2

Prescription Pharmacological Options

First-Line: Dextromethorphan

Dextromethorphan is the preferred prescription antitussive due to superior safety profile compared to opioid alternatives 1, 2, 3:

• Dosing: 30-60 mg for optimal cough suppression, with maximum daily dose of 120 mg 1, 2
• Key consideration: Standard over-the-counter dosing (10-15 mg) is often subtherapeutic; maximum cough reflex suppression occurs at 60 mg 1, 2
• Caution: Check combination products carefully to avoid excessive acetaminophen or other ingredients when prescribing higher doses 1, 2
• Mechanism: Non-sedating opiate that centrally suppresses the cough reflex 1, 3

Important limitations of dextromethorphan:

• Evidence for efficacy is mixed, with some studies showing no significant difference from placebo 1, 4, 5
• Should not be used for productive cough where secretion clearance is beneficial 2
• Not recommended for routine use in acute bronchitis due to inconsistent results 2
• Contraindication: Do not use if taking MAOIs or within 2 weeks of stopping MAOI 3

Alternative Options for Specific Situations

For nocturnal cough disrupting sleep:

• First-generation sedative antihistamines can suppress cough and are particularly useful due to sedative effects 1, 2
• The sedation is actually valuable when cough disturbs sleep 1, 6

For quick but temporary relief:

• Menthol by inhalation suppresses cough reflex acutely but effect is short-lived 1, 2
• Can be prescribed as menthol crystals or proprietary capsules 1

What NOT to Prescribe

Codeine and pholcodine are NOT recommended:

• No greater efficacy than dextromethorphan 1, 2
• Significantly worse adverse effect profile including drowsiness, nausea, constipation, and physical dependence 1, 2
• Poor benefit-to-risk ratio 2

Promethazine is NOT recommended:

• No established efficacy for cough suppression 2
• Primarily used for nausea, allergic conditions, and sedation, not cough 2

Duration-Based Algorithm

Acute Cough (< 3 weeks)

1. First: Honey and lemon, voluntary cough suppression 1, 2
2. If inadequate relief: Dextromethorphan 30-60 mg 1, 2
3. For nighttime cough: Add first-generation antihistamine 1, 2
4. For quick relief: Menthol inhalation 1, 2

Post-Infectious Cough (3-8 weeks after URI)

1. First-line: Inhaled ipratropium 1, 2
2. Second-line: Inhaled corticosteroids if quality of life affected 1
3. For severe paroxysms: Prednisone 30-40 mg daily for short course after ruling out other causes 1, 2
4. Last resort: Central antitussives like dextromethorphan only when other measures fail 1, 2

Chronic Cough (> 8 weeks)

Stop antitussive therapy and perform full diagnostic workup to evaluate for alternative diagnoses 1, 2:

• Test for bronchial hyperresponsiveness and eosinophilic bronchitis 1
• Assess for GERD (may require intensive PPI therapy for ≥3 months) 1
• Consider upper airway symptoms (trial topical corticosteroid) 1
• If unexplained: multimodality speech pathology therapy, then consider gabapentin 1

Common Pitfalls to Avoid

• Using subtherapeutic doses of dextromethorphan (10-15 mg) that may not provide adequate relief 1, 2
• Prescribing codeine-based antitussives which have no efficacy advantage but increased side effects 1, 2
• Continuing antitussive therapy beyond 3 weeks without diagnostic workup 2
• Not recognizing GERD as a cause for persistent cough, which may occur without GI symptoms 1
• Using dextromethorphan for productive cough where secretion clearance is needed 2