What are the causes and management options for acute dry cough?

Management of Acute Dry Cough

Causes of Acute Dry Cough

Acute dry cough is most commonly caused by viral upper respiratory tract infections, with other important causes including post-infectious cough, asthma exacerbations, allergic rhinitis, gastroesophageal reflux disease (GORD), and medication-induced cough (particularly ACE inhibitors). 1

Common Etiologies

• Viral upper respiratory tract infections are the predominant cause of acute dry cough in primary care settings 2
• Post-infectious cough can persist for weeks after the initial infection resolves 3
• Asthma or anaphylaxis should be considered when cough presents with increasing breathlessness 1
• Allergic conditions with upper airway symptoms may manifest as dry cough 1, 4
• GORD is a common but often overlooked cause, and may occur without gastrointestinal symptoms 1
• ACE inhibitor therapy is a medication-related cause that should be identified through medication history 5

Red Flags Requiring Specialist Referral

• Significant hemoptysis warrants immediate specialist evaluation 1
• Possible foreign body inhalation requires urgent assessment 1
• Cough with fever, malaise, and purulent sputum may indicate serious lung infection requiring further investigation 1
• Cough lasting more than 7 days with fever, rash, or persistent headache could indicate a serious underlying condition 6

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Management Approach

First-Line Non-Pharmacological Treatment

Simple home remedies like honey and lemon should be the initial treatment for acute dry cough, as they are often as effective as pharmacological options and carry no side effects. 1, 7, 3

• Honey and lemon mixtures are recommended by the British Thoracic Society as the simplest, cheapest, and often effective first-line treatment 1, 7
• Voluntary cough suppression through central modulation of the cough reflex may be sufficient to reduce cough frequency in some patients 1, 3
• Smoking cessation should be strongly encouraged for smokers, as it leads to significant remission in cough symptoms 1

Pharmacological Management

When non-pharmacological measures fail and the cough is bothersome (especially disrupting sleep), dextromethorphan is the preferred antitussive due to its superior efficacy and safety profile compared to codeine-based alternatives. 1, 7, 3

Preferred Agent: Dextromethorphan

• Dextromethorphan 30-60 mg is the recommended first-line pharmacological option 1, 7, 3
• Maximum cough reflex suppression occurs at 60 mg, which is higher than standard over-the-counter dosing 1, 7, 3
• Standard OTC dosing is often subtherapeutic and may not provide adequate relief 3
• Use with caution as some combination preparations contain additional ingredients like paracetamol or other pain relievers 1, 3
• Do not use with MAOIs or within 2 weeks of stopping MAOI therapy 6
• Avoid in patients with chronic cough from smoking, asthma, or emphysema, or when cough occurs with excessive phlegm 6

Alternative Options for Specific Situations

For nocturnal cough disrupting sleep, first-generation antihistamines with sedative properties are particularly useful due to their dual action of cough suppression and sedation. 1, 7, 3

• First-generation sedative antihistamines (e.g., chlorpheniramine) suppress cough and are especially suitable for nighttime use 1, 7, 3, 8
• Menthol inhalation provides acute but short-lived cough suppression and can be prescribed as menthol crystals or proprietary capsules 1, 7, 3
• The effect of menthol is immediate but temporary, making it useful for quick relief 1

Special Considerations for Severe Post-Infectious Cough

• Inhaled ipratropium should be tried before central antitussives for post-infectious cough 3
• Prednisone 30-40 mg daily for a short period may be considered for severe paroxysms of post-infectious cough 3
• If pertussis is suspected, macrolide antibiotics are indicated with isolation for 5 days from treatment start 3

What NOT to Use

Codeine and pholcodine should be avoided as they have no greater efficacy than dextromethorphan but carry significantly more adverse effects including drowsiness, nausea, constipation, and risk of physical dependence. 1, 7, 3

• Codeine has no proven benefit over dextromethorphan in acute cough 2, 1, 7
• Expectorants, mucolytics, antihistamines (non-sedating), and bronchodilators should not be prescribed for uncomplicated acute dry cough as evidence for benefit is lacking 2
• Guaifenesin is indicated only for productive cough to loosen phlegm, not for dry cough 9

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Practical Treatment Algorithm

Step 1: Initial Assessment

• Rule out red flags (hemoptysis, foreign body, severe breathlessness, prolonged fever) 1, 6
• Assess cough characteristics: dry vs. productive, duration, severity, impact on sleep 2
• Review medications for ACE inhibitors or other potential causes 1, 5

Step 2: First-Line Treatment (Days 1-3)

• Start with honey and lemon mixtures for symptomatic relief 1, 7, 3
• Encourage voluntary cough suppression techniques 1, 3
• Reassure patient that most acute cough is self-limiting and lasts 1-3 weeks 2

Step 3: Pharmacological Treatment (If Needed After Day 3-4)

• For daytime bothersome cough: Dextromethorphan 30-60 mg three times daily 1, 7, 3
• For nocturnal cough disrupting sleep: First-generation antihistamine (e.g., chlorpheniramine) at bedtime 1, 7, 3, 8
• For quick temporary relief: Menthol inhalation as needed 1, 7, 3

Step 4: Persistent Cough (>7 Days)

• Re-evaluate for underlying causes: GORD, asthma, post-nasal drip 1
• Consider trial of topical corticosteroid if upper airway symptoms present 1
• Consider intensive acid suppression with PPI for at least 3 months if GORD suspected 1
• Perform bronchial provocation testing if chronic cough with normal spirometry and no obvious cause 1

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Common Pitfalls to Avoid

• Using subtherapeutic doses of dextromethorphan (standard OTC dosing may be inadequate; consider 60 mg for optimal effect) 1, 7, 3
• Prescribing codeine-based antitussives which offer no advantage but increased side effects 1, 7, 3
• Failing to consider GORD as a cause for persistent cough, especially when gastrointestinal symptoms are absent 1
• Using antitussives for productive cough where clearance of secretions is beneficial 3, 6
• Not recognizing that most acute viral cough is self-limiting and does not require prescribed medication 1
• Overlooking medication history for ACE inhibitors as a reversible cause 1, 5
• Ignoring the need to adjust chronic disease medications (asthma, COPD, cardiac failure, diabetes) during acute respiratory infections 2