How to manage a 3-week persistent cough in a patient on Tussin (dextromethorphan)?

Management of Persistent Cough After Three Weeks on Dextromethorphan

For a patient with cough persisting for three weeks despite dextromethorphan use, switch to inhaled ipratropium bromide as first-line therapy for post-infectious cough, followed by inhaled corticosteroids if needed. 1, 2

Diagnosis: Post-Infectious Cough

• A cough persisting for 3-8 weeks following symptoms of an acute respiratory infection should be classified as post-infectious cough 1, 2
• Standard diagnostic workup should include chest radiograph and spirometry to rule out other causes 1
• Dextromethorphan is often ineffective for post-infectious cough as it is primarily indicated for acute viral cough 3

First-Line Treatment

• Discontinue dextromethorphan as it is only recommended when other measures fail for post-infectious cough 1, 2
• Start inhaled ipratropium bromide which has demonstrated efficacy in attenuating post-infectious cough in controlled trials 1, 2
• Antibiotics have no role in treatment unless there is confirmed bacterial infection 1, 2

Second-Line Treatment

• If cough persists despite ipratropium, add inhaled corticosteroids when the cough adversely affects quality of life 1, 2
• Inhaled corticosteroids work by suppressing airway inflammation and bronchial hyperresponsiveness 2
• Consider a two-week oral steroid trial if there is suspicion of eosinophilic airway inflammation 1

For Severe Cases

• For severe paroxysms of post-infectious cough, consider prednisone 30-40 mg daily for a short, finite period 1, 2
• This should only be considered after ruling out other common causes of cough such as upper airway cough syndrome, asthma, or gastroesophageal reflux disease 1, 2

Rule Out Other Common Causes

• Upper Airway Cough Syndrome (UACS): Consider a trial of first-generation antihistamine-decongestant if nasal symptoms are present 1
• Gastroesophageal Reflux Disease (GERD): Consider intensive acid suppression with proton pump inhibitors if reflux symptoms are present 1
• Asthma: Consider bronchial provocation testing if normal spirometry 1
• ACE Inhibitors: Discontinue if patient is taking these medications 1

Special Considerations

• If cough has persisted beyond 8 weeks, reclassify as chronic cough and evaluate for other causes 1, 4
• Consider pertussis if cough is accompanied by paroxysms, post-tussive vomiting, or inspiratory whooping sound 1
• If pertussis is suspected, obtain nasopharyngeal culture and treat with macrolide antibiotics 1

Common Pitfalls to Avoid

• Using subtherapeutic doses of dextromethorphan (optimal dose is 60 mg for cough suppression) 3
• Continuing to use central antitussives when they are ineffective for post-infectious cough 1
• Failing to recognize that post-infectious cough is often multifactorial and may require treatment of multiple underlying causes 1
• Inappropriate use of antibiotics for non-bacterial causes of post-infectious cough 1, 2

Follow-up Recommendations

• Follow up within 4-6 weeks after initial treatment 2
• If cough persists despite optimal therapy, consider referral to a specialist cough clinic 1
• Consider high-resolution CT scan if other targeted investigations are normal 1