Contraindications to Robitussin (Dextromethorphan)
The primary absolute contraindication to dextromethorphan is concurrent use with monoamine oxidase inhibitors (MAOIs), which can precipitate a dangerous serotonergic reaction. 1, 2
Absolute Contraindications
MAOI use: Dextromethorphan is strictly contraindicated when taken concurrently with monoamine oxidase inhibitors or within 14 days of discontinuing MAOI therapy, as this combination can cause severe serotonergic reactions including hyperthermia, rigidity, autonomic instability, and altered mental status. 1, 2
Sulfite allergy: Formulations containing sodium metabisulfite (such as extended-release dextromethorphan polistirex) are contraindicated in patients with known sulfite hypersensitivity, as this can trigger allergic-type reactions ranging from mild symptoms to severe anaphylaxis. 3
Relative Contraindications and Major Precautions
While not absolute contraindications, the following warrant extreme caution or avoidance:
Pregnancy and breastfeeding: Although not explicitly stated as an absolute contraindication in the evidence for dextromethorphan specifically, the general principle from weight management medications suggests caution in reproductive contexts. 1
Chronic cough with excessive secretions: Dextromethorphan suppresses the cough reflex, which could be problematic in conditions requiring productive cough for airway clearance. 4
Severe hepatic impairment: Given dextromethorphan's hepatic metabolism and documented pharmacokinetic polymorphism, severe liver disease may lead to drug accumulation, though short-term use appears relatively safe. 2
Clinical Pitfalls to Avoid
Drug interactions beyond MAOIs: Be vigilant for other serotonergic medications (SSRIs, SNRIs, tricyclic antidepressants) that could theoretically increase serotonin syndrome risk when combined with dextromethorphan, though this is less severe than with MAOIs. 2
Abuse potential: Dextromethorphan has documented abuse liability at supratherapeutic doses due to its NMDA receptor antagonism, producing dissociative effects similar to ketamine or phencyclidine. 2, 5 Screen for history of substance abuse before prescribing.
Overdose considerations: While generally safe even in overdose compared to opioid antitussives, high doses can cause neurological, cardiovascular, and gastrointestinal disturbances. 2