Linezolid is a reversible MAO inhibitor. Dextromethorphan is a weak serotonin reuptake inhibitor and sigma-1 agonist. The combination produces synaptic serotonin accumulation and serotonin syndrome.
Symptoms
Within hours of co-administration: agitation, confusion, tachycardia, hypertension, hyperthermia, tremor, myoclonus, hyperreflexia. Severe cases – seizures, coma, rhabdomyolysis.
Management
Avoid dextromethorphan for the linezolid course (typically 7–14 days). Alternative antitussives: guaifenesin or honey for nocturnal cough. If dextromethorphan was already taken, stop linezolid; serotonin syndrome resolves within 24 hours.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.