Is Polytussin DM (dextromethorphan) safe to use in patients with asthma?

Can Polytussin DM Be Used in Patients with Asthma?

Yes, Polytussin DM (dextromethorphan) can be safely used in patients with asthma for symptomatic cough relief, as it does not worsen asthma symptoms and has a favorable safety profile. However, it should not be expected to treat the underlying asthma itself.

Key Safety Considerations

Dextromethorphan Does Not Treat Asthma

• Dextromethorphan is a central cough suppressant that acts on the cough reflex center in the brain, not on the airways 1
• It should never be used as a substitute for appropriate asthma controller medications like inhaled corticosteroids 2
• The ARIA guidelines explicitly state that combination antihistamine-decongestant products should not be used to treat asthma symptoms in patients with allergic rhinitis and asthma 2

When to Use Dextromethorphan in Asthma Patients

For symptomatic cough relief only:

• Use dextromethorphan when cough is due to upper respiratory infection or postinfectious causes, not for asthma-related cough 2, 1
• Standard over-the-counter dosing (15-30 mg) is often subtherapeutic; optimal cough suppression occurs at 60 mg 1
• Consider it only after other measures fail for postinfectious cough 2

Dextromethorphan has advantages over codeine:

• Superior safety profile with fewer adverse effects (no drowsiness, nausea, constipation, or physical dependence) 1, 3
• Equal or greater efficacy in reducing cough intensity compared to codeine 3
• Safe even in overdose situations 4

Critical Pitfalls to Avoid

Do Not Use for Asthma-Related Cough

• If cough is due to poorly controlled asthma, optimize asthma therapy with inhaled corticosteroids first 2
• Albuterol is not recommended for acute or chronic cough not due to asthma 2
• Inhaled corticosteroids remain the first-line controller medication for persistent asthma of all severities 5

Assess the Underlying Cause

• If cough persists beyond 8 weeks, consider diagnoses other than postinfectious cough 2
• Rule out bacterial sinusitis, pertussis, gastroesophageal reflux disease, or upper airway cough syndrome before using antitussives 2
• For suspected pertussis (paroxysmal cough with posttussive vomiting or inspiratory whoop), use macrolide antibiotics, not dextromethorphan 2

Dosing Considerations

• Use 30-60 mg for adequate cough suppression rather than standard OTC doses 1
• Be cautious with combination products that may contain acetaminophen or other ingredients at higher doses 1
• Avoid concurrent use with monoamine oxidase inhibitors due to potential drug interactions 4

Practical Algorithm for Cough in Asthma Patients

1. First, determine if cough is asthma-related:

   • If yes: optimize asthma controller therapy (inhaled corticosteroids) 2
   • If no: proceed to step 2

2. For non-asthma cough (URI, postinfectious):

   • Start with honey and lemon for benign viral cough 1
   • If additional relief needed, use dextromethorphan 30-60 mg 1
   • For nocturnal cough, consider first-generation antihistamines 1

3. For postinfectious cough:

   • Try inhaled ipratropium first 2
   • For severe paroxysms, consider prednisone 30-40 mg daily for short course 2
   • Use dextromethorphan only when other measures fail 2

Bottom Line

Polytussin DM is safe for symptomatic cough relief in asthma patients when the cough is not due to uncontrolled asthma itself. Ensure asthma is adequately controlled with appropriate controller medications, and use dextromethorphan at effective doses (30-60 mg) for short-term symptomatic relief of cough from other causes 1, 3.