Promethazine for Non-Productive Cough
Promethazine is not recommended for treating non-productive cough in healthy adults, as it has no established efficacy for cough suppression and carries significant risks including sedation, respiratory depression, and extrapyramidal reactions. 1
Why Promethazine Should Be Avoided
The American College of Physicians explicitly states that promethazine has no established efficacy for cough suppression and is primarily indicated for nausea, allergic conditions, and sedation—not cough management. 1
The British Thoracic Society recommends against using promethazine for cough management, as it is not indicated for this purpose. 1
Promethazine carries serious adverse effects including hypotension, respiratory depression, neuroleptic malignant syndrome, and extrapyramidal reactions such as restlessness and oculogyric crises. 1
Historical pediatric data demonstrates that promethazine has caused significant sedation, agitation, hallucinations, seizures, and dystonic reactions, raising concerns about its safety profile even in adults. 2
Recommended First-Line Treatment Algorithm
Step 1: Non-Pharmacological Approaches
Start with simple home remedies like honey and lemon, which may be as effective as pharmacological treatments for benign viral cough. 1
Teach voluntary cough suppression techniques, as central modulation may be sufficient to reduce cough frequency in some patients. 1
Step 2: Pharmacological Treatment When Needed
Use dextromethorphan as the first-line antitussive agent due to its superior safety profile compared to all alternatives, including promethazine. 1
Dose dextromethorphan at 30-60 mg per dose for optimal cough suppression (maximum 120 mg daily), as standard over-the-counter dosing is often subtherapeutic. 1
Maximum cough reflex suppression occurs at 60 mg and can be prolonged at this level. 1
Step 3: Nocturnal Cough Management
For nighttime cough disrupting sleep, consider first-generation sedative antihistamines (excluding promethazine) because their sedative properties help reduce cough while promoting sleep. 1
These agents are particularly suitable when cough is preventing rest, but drowsiness is an expected side effect. 3
Step 4: Adjunctive Short-Term Relief
- Menthol inhalation (menthol crystals or proprietary capsules) provides acute but short-lived cough suppression for temporary symptom relief. 1
Critical Prescribing Pitfalls to Avoid
Never prescribe codeine-containing products for cough, as they have no greater efficacy than dextromethorphan but significantly more adverse effects including drowsiness, nausea, constipation, and physical dependence. 1
Avoid subtherapeutic doses of dextromethorphan (less than 30 mg), which may fail to provide adequate relief. 1
Exercise caution with higher doses of dextromethorphan in combination preparations, as some contain acetaminophen or other ingredients that could reach toxic levels. 1
Do not use promethazine simply because it is an antihistamine—it lacks cough suppression efficacy and has a worse safety profile than appropriate alternatives. 1
When to Reassess
If cough persists beyond 3 weeks, discontinue antitussive therapy and perform a full diagnostic workup to evaluate for alternative diagnoses rather than continuing symptomatic treatment. 1
For postinfectious cough lasting beyond the acute phase, consider inhaled ipratropium before central antitussives, and reserve dextromethorphan for cases where ipratropium fails. 1
For severe paroxysms of postinfectious cough unresponsive to initial measures, a short course of prednisone 30-40 mg daily may be indicated. 1