Metronidazole Drug Interactions — NDEB AFK MCQ
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Correct answer: D — Check for concurrent alcohol use and warfarin therapy
Metronidazole has a disulfiram-like reaction with alcohol (inhibits aldehyde dehydrogenase, causing nausea, vomiting, flushing, tachycardia). Patients must avoid all alcohol during and for 48 hours after treatment. Metronidazole also potentiates warfarin's anticoagulant effect by inhibiting its hepatic metabolism (CYP enzymes), increasing INR and bleeding risk. These two interactions must be specifically checked before prescribing. Patients on lithium should also be monitored as metronidazole can increase lithium levels.
Reference: Katzung – Basic and Clinical Pharmacology, 15th ed., 2021