Role of Dextromethorphan in Cough Management
Dextromethorphan (DM) has limited efficacy for cough management and should be considered only when other measures fail, particularly for short-term symptomatic relief of coughing. 1
Mechanism and Efficacy
- Dextromethorphan is a non-sedating opiate that acts centrally to suppress the cough reflex 1
- DM has been shown to reduce cough frequency in some studies, but results are inconsistent across different patient populations 1
- At standard doses (30mg), DM may provide modest reduction in cough counts and cough effort (19-36%) in adults with upper respiratory infections 1
- There is a dose-response relationship, with maximum cough reflex suppression occurring at 60mg, which is higher than typically recommended in over-the-counter preparations 1
Clinical Applications
- DM is FDA-approved for temporary relief of cough due to minor throat and bronchial irritation, such as with the common cold or inhaled irritants 2
- DM is most appropriate for short-term symptomatic relief in acute cough, particularly when the cough interferes with sleep 2, 1
- For patients with acute bronchitis, antitussive agents like DM can be offered for short-term symptomatic relief (Grade of recommendation C) 1
- DM has replaced codeine as the most widely used cough suppressant due to its better safety profile at directed doses 3
Limitations and Considerations
- Evidence for DM efficacy is mixed, with some studies showing no significant difference compared to placebo in cough frequency or severity 1
- DM should not be used for productive cough where clearance of secretions is beneficial 1
- Central acting antitussives like DM should be considered only when other measures fail for postinfectious cough 1
- DM is not recommended for routine use in acute bronchitis due to inconsistent results 1
Safety Concerns
- DM is subject to abuse when consumed at inappropriately high doses (over 1500 mg/day), which can induce psychosis characterized by delusions, hallucinations, and paranoia 3
- Recreational misuse of DM (known as "robotripping") can result in a manic toxidrome including psychomotor agitation, hostility, grandiose behavior, and hallucinations 4
- Severe DM poisoning can cause serotonin syndrome requiring intensive medical intervention 5
Comparison with Other Antitussives
- DM has a better safety profile than codeine or pholcodine, with fewer adverse effects 1, 6
- In a direct comparison study, both DM and codeine (20mg doses) were similarly effective in reducing cough frequency, but DM was superior in reducing cough intensity 6
- Benzonatate offers an alternative to DM with a different adverse effect profile and may be preferred when opioids are contraindicated 7
Recommendations for Clinical Practice
- For acute viral cough, simple measures like honey and lemon may be as effective as pharmacological treatments 1
- When pharmacological treatment is needed, DM at appropriate doses (30-60mg) can be considered for short-term use 1
- For children, honey may be more effective than DM for cough relief 8
- Always assess cough characteristics and duration before considering DM therapy, and rule out serious underlying causes requiring specific treatment 7
- In patients with postinfectious cough, consider other treatments first (such as inhaled ipratropium) before using central acting antitussives like DM 1
Cautions
- DM should be avoided in patients at risk for substance abuse due to its potential for misuse 3, 4
- Extended-release formulations should be used as directed and not at higher doses than recommended 2
- Some DM preparations contain additional ingredients like sodium metabisulfite that may cause allergic reactions in susceptible individuals 2