How should I treat a severe dry cough in an adult without red‑flag symptoms?

Treatment of Severe Dry Cough in Adults

For a severe dry cough without red-flag symptoms, start with honey and lemon as first-line therapy, which is as effective as pharmacological treatments at no cost, and if pharmacological intervention is needed, use dextromethorphan 30-60 mg (not the standard 15-30 mg OTC dose, which is subtherapeutic) for short-term relief only. 1

Initial Assessment and Red Flags

Before treating symptomatically, rule out conditions requiring specific intervention: 2

• Haemoptysis – requires immediate investigation
• Prominent systemic illness – suggests bacterial pneumonia or other serious pathology
• Suspicion of inhaled foreign body – requires bronchoscopy
• Suspicion of lung cancer – particularly in smokers or those with weight loss

If none of these are present and the cough is acute (less than 3 weeks), it is almost certainly viral and self-limiting. 2, 1

First-Line Non-Pharmacological Treatment

Honey and lemon is the recommended first-line treatment because: 2, 1

• Patients report equivalent benefit to over-the-counter preparations
• There is little evidence of specific pharmacological effect from most OTC products
• It costs nothing and has no adverse effects
• Simple voluntary suppression and central modulation of the cough reflex may be sufficient

Pharmacological Options When Needed

Dextromethorphan (Preferred Agent)

Use 30-60 mg for short-term relief (typically less than 7 days): 2, 1, 3

• The standard OTC dose of 15-30 mg is subtherapeutic
• Maximum cough reflex suppression occurs at 60 mg
• Maximum daily dose should not exceed 120 mg
• This is a non-sedating opiate with proven efficacy in meta-analysis
• Critical pitfall: Check combination products carefully, as some contain paracetamol or other ingredients that can accumulate to toxic levels at higher dextromethorphan doses 3

Menthol Inhalation

Menthol by inhalation suppresses the cough reflex acutely but is short-lived: 2

• Can be prescribed as menthol crystals BPC or proprietary capsules
• Useful for immediate but temporary relief

First-Generation Antihistamines (For Nocturnal Cough Only)

Sedating antihistamines like diphenhydramine or chlorpheniramine may be suitable specifically for nocturnal cough: 2, 3

• They suppress cough but cause drowsiness
• Caution in elderly: Avoid in patients with cognitive impairment, urinary retention, or fall risk due to anticholinergic effects 3
• Should not be used routinely during daytime

Benzonatate

FDA-approved for symptomatic relief of cough, though less commonly discussed in guidelines. 4

What NOT to Use

Codeine and pholcodine are NOT recommended: 2, 1, 3

• No greater efficacy than dextromethorphan
• Significantly greater adverse side effect profile (drowsiness, nausea, constipation, physical dependence)
• Poor benefit-to-risk ratio, especially in elderly patients

N-acetylcysteine should NOT be used for acute dry cough: 5

• Shows no consistent favorable effect on cough in acute bronchitis
• Multiple trials have failed to demonstrate reproducible benefit
• Only narrowly indicated for stable chronic bronchitis to reduce exacerbation frequency, not for acute cough relief

Duration and Follow-Up

• Acute viral cough typically resolves within 3 weeks 2, 1
• If cough persists beyond 3 weeks, discontinue antitussive therapy and pursue full diagnostic workup for chronic cough 1, 3
• Chronic cough (>8 weeks) requires systematic evaluation including chest radiograph and spirometry 2

Common Underlying Causes to Consider

If the cough is not resolving or is recurrent, consider: 2

• Asthma (cough may be the only manifestation) – trial of oral steroids for 2 weeks
• ACE inhibitor use – discontinue if present
• Gastro-oesophageal reflux (may occur without GI symptoms) – intensive acid suppression with PPIs for minimum 3 months
• Upper airway disease/rhinosinusitis – trial of topical nasal corticosteroid for 1 month
• Smoking – cessation leads to significant remission

Key Clinical Pitfalls to Avoid

• Do not prescribe subtherapeutic doses of dextromethorphan (15-30 mg) 1, 3
• Do not prescribe codeine-based products – they offer no advantage and cause more harm 2, 1, 3
• Do not prescribe antibiotics reflexively – most acute cough is viral and antibiotics contribute to antimicrobial resistance 1
• Do not suppress productive cough – secretion clearance is beneficial 3
• Do not continue antitussives beyond short-term use – if cough persists beyond 3 weeks, investigate rather than continue symptomatic treatment 1, 3