A 30-year-old patient on anti-TB therapy develops tingling and numbness in hands and feet after 2 months. The responsible drug acts by competing with pyridoxine (Vitamin B6). This side effect is most common in:

• A Fast acetylators taking standard doses
• B Slow acetylators due to drug accumulation ✓
• C Patients with normal renal function
• D Patients taking rifampicin concurrently

Explanation

Isoniazid (INH) peripheral neuropathy results from its structural competition with pyridoxine (vitamin B6), inhibiting pyridoxal phosphate-dependent enzymes essential for sphingolipid synthesis and axonal function. Slow acetylators (who have lower N-acetyltransferase-2 activity) metabolize INH more slowly, resulting in higher plasma drug concentrations and greater risk of peripheral neuropathy. Pyridoxine supplementation (10-25 mg/day) prevents this complication. Other INH toxicities include hepatotoxicity, lupus-like syndrome, and pellagra (by depleting niacin).

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.