Isoniazid is metabolized by N-acetyltransferase 2 (NAT2). A patient on isoniazid is a fast acetylator. Compared to a slow acetylator, what is this patient at increased risk of developing?

• A Peripheral neuropathy
• B Hemolytic anemia
• C Systemic lupus erythematosus
• D Hepatotoxicity ✓

Explanation

Fast acetylators convert isoniazid to acetylisoniazid rapidly, which is then hydrolyzed to acetylhydrazine. Acetylhydrazine is oxidized by CYP2E1 to a reactive hepatotoxic metabolite. Slow acetylators accumulate more parent drug, leading to peripheral neuropathy due to pyridoxine depletion.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.