What can I give for a dry cough lasting one month?

Management of Dry Cough Lasting One Month

For a dry cough persisting for one month (4 weeks), you should first consider post-infectious cough and initiate a trial of inhaled ipratropium bromide as first-line therapy, followed by dextromethorphan 60 mg if ipratropium fails, and reserve short-course oral corticosteroids for severe paroxysmal coughing. 1, 2

Initial Assessment and Key Considerations

At one month duration, this cough falls into the subacute category (3-8 weeks), which has distinct management implications compared to acute or chronic cough 1:

• Rule out pertussis immediately if there are paroxysmal coughing fits, post-tussive vomiting, or inspiratory whooping sounds—these patients require macrolide antibiotics (azithromycin 500 mg daily for 3-5 days) and isolation for 5 days 1, 3, 4
• Stop ACE inhibitors if the patient is taking them, regardless of temporal relationship to cough onset; resolution typically occurs within 1-4 weeks but may take up to 3 months 1
• Address smoking if applicable—cessation is first-line treatment with most coughs resolving within 4 weeks 1, 3
• Assess for occupational/environmental exposures that may perpetuate airway irritation 1

Treatment Algorithm for Post-Infectious Dry Cough

First-Line: Inhaled Ipratropium

• Inhaled ipratropium bromide should be tried before central antitussives as it may attenuate the cough by reducing mucus hypersecretion and addressing bronchial hyperresponsiveness 1, 2, 4

Second-Line: Dextromethorphan

If ipratropium fails or provides insufficient relief:

• Dextromethorphan 60 mg is the optimal dose for maximum cough reflex suppression—standard over-the-counter doses (15-30 mg) are subtherapeutic 2, 3, 4
• Dextromethorphan has a superior safety profile compared to codeine with equivalent efficacy 1, 2
• Avoid codeine—it offers no greater efficacy than dextromethorphan but has significantly more adverse effects (drowsiness, nausea, constipation, physical dependence) 2, 5

Third-Line: Corticosteroids

For severe paroxysmal coughing that persists despite the above measures:

• Prednisone 30-40 mg daily for a short, finite period when other common causes have been ruled out 1, 2, 3
• Inhaled corticosteroids may be considered if cough adversely affects quality of life and persists despite ipratropium 1

Adjunctive Measures

• Simple home remedies like honey and lemon may be as effective as pharmacological treatments for benign viral cough 2
• First-generation sedating antihistamines (e.g., chlorpheniramine) can be particularly useful for nocturnal cough disrupting sleep, though they cause drowsiness 2, 5
• Menthol inhalation provides acute but short-lived relief 2

When to Escalate or Reassess

• At 8 weeks (2 months), if cough persists, it transitions to chronic cough requiring full diagnostic workup including chest radiography, spirometry, and evaluation for asthma, upper airway cough syndrome, gastroesophageal reflux disease, and eosinophilic bronchitis 1, 6
• Red flags requiring immediate further investigation: hemoptysis, constitutional symptoms (fever, weight loss, night sweats), respiratory distress, or risk factors for malignancy 1, 3

Critical Pitfalls to Avoid

• Do not use antibiotics for post-infectious viral cough—they have no role unless bacterial sinusitis or pertussis is confirmed 1, 3
• Do not use subtherapeutic doses of dextromethorphan; over-the-counter preparations typically contain insufficient amounts 2, 3
• Do not prescribe codeine as first-line—it has no efficacy advantage over dextromethorphan but significantly worse side effects 1, 2, 4
• Do not overlook ACE inhibitor-induced cough—it can occur months after starting therapy and may persist even if cough preceded the medication 1
• Do not miss pertussis—any cough at this duration with paroxysmal features warrants empiric macrolide treatment without waiting for laboratory confirmation 1, 3, 4