A woman receiving oral metronidazole for trichomoniasis attends a party and drinks wine, developing flushing, throbbing headache, nausea and palpitations within minutes. The basis of this reaction is:

• A Metronidazole inhibits aldehyde dehydrogenase, causing acetaldehyde accumulation ✓
• B Metronidazole induces gastric mucosal histamine release
• C Metronidazole forms a toxic adduct with ethanol itself
• D Metronidazole potentiates ethanol absorption through gastric ATB transporters

Explanation

Metronidazole produces a classic disulfiram-like reaction with alcohol. It inhibits aldehyde dehydrogenase, so ingested ethanol accumulates as acetaldehyde, causing vasodilatation, headache, nausea, sweating and hypotension. Patients must abstain from alcohol during therapy and for at least a day afterward. This shared property with disulfiram underlies the warning label on all nitroimidazoles. The other options describe nonexistent mechanisms.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.