What is the best cough treatment for a patient with a history of substance use disorder and a dry cough, given previous recommendations for dextromethorphan?

Dextromethorphan Should NOT Be Used in Patients with Substance Use Disorder

For patients with a history of substance use disorder and dry cough, dextromethorphan is contraindicated due to its significant abuse and addiction potential, and alternative non-addictive therapies should be used instead.

Why Dextromethorphan Is Problematic in This Population

Abuse and Addiction Liability

• Dextromethorphan has well-documented abuse potential, particularly when consumed at doses exceeding therapeutic levels (>1500 mg/day), inducing PCP-like psychotic symptoms including delusions, hallucinations, and paranoia 1
• The drug produces a reproducible substance dependence syndrome with physical withdrawal symptoms, despite being commonly perceived as non-addictive 2, 3
• Dextromethorphan acts through serotonergic and sigma-1 opioid receptors, with its active metabolite dextrorphan functioning as an NMDA receptor antagonist, creating dissociative effects that users actively seek 3
• Case reports document severe dextromethorphan use disorder requiring treatment with antipsychotics and mood stabilizers, with patients experiencing intense cravings that prevented abstinence 1, 4

Clinical Implications for Substance Use Disorder Patients

• Patients with substance use disorder are at heightened risk for cross-addiction and should avoid medications with abuse potential 3
• Dextromethorphan is not detected on standard urine drug screens, making monitoring of abuse difficult in this vulnerable population 1
• The drug is readily available over-the-counter in over 140 preparations, creating easy access for potential misuse 1, 5

Recommended Alternatives for Dry Cough in This Population

First-Line Non-Pharmacological Approach

• Honey and lemon mixture is the safest initial treatment, with evidence of patient-reported benefit and zero abuse potential 6
• Voluntary cough suppression through central modulation may be sufficient to reduce cough frequency without any medication 6

Pharmacological Alternatives Without Abuse Potential

• Menthol inhalation provides acute cough reflex suppression when inhaled, with effects that are short-lived but effective, and can be prescribed as menthol crystals or proprietary capsules 6
• Ipratropium bromide inhaled is effective for cough suppression in upper respiratory infections without addiction risk 6
• Glycerol-based cough syrups show evidence of cough reduction and have a favorable safety profile with no abuse potential 7, 8

For Severe Nocturnal Cough Only

• First-generation sedating antihistamines (such as chlorpheniramine or diphenhydramine) can suppress cough through sedative properties, particularly useful for nocturnal cough 8, 6
• While these have some abuse potential, it is significantly lower than dextromethorphan and they are less commonly sought by individuals with substance use disorder 6

Critical Pitfall to Avoid

The most important error would be prescribing dextromethorphan to a patient with substance use disorder based on its reputation as a "safe" over-the-counter medication. The evidence clearly demonstrates that dextromethorphan has significant addiction liability with documented cases of dependence, withdrawal, and substance-induced psychosis 1, 2, 3, 4. This directly contradicts its use in any patient with a history of substance use disorder.

Treatment Algorithm for This Patient

1. Start with honey and lemon mixture as the simplest, safest, and often effective first-line approach 6
2. Add menthol inhalation for acute symptom relief if needed, recognizing the effect is short-lived 6
3. Consider ipratropium bromide inhaled if cough persists and is significantly impacting quality of life 6
4. Reserve sedating antihistamines specifically for nocturnal cough that disrupts sleep 8, 6
5. Never use dextromethorphan, codeine, or other opioid-based antitussives in this population due to addiction risk 8, 6, 1, 3