Question

Treatment with INH (isoniazid) leads to deficiency of which vitamin?

• A. Thiamine
• B. Niacin
• C. Pyridoxine
• D. Pantothenic acid

Hint:

INH mimics vitamin B6 and triggers a neuropathy unless that vitamin is replaced.

Answer 1

The Correct Option is C

Isoniazid is a structural analogue of vitamin B6, and that resemblance is the whole story. By competing with pyridoxine, INH both promotes its renal loss and blocks the kinase that activates it to pyridoxal phosphate, leaving the body short of usable B6. The most visible result is a dose-related peripheral neuropathy, prevented by giving supplemental pyridoxine alongside the drug. None of the other vitamins offered, thiamine, niacin or pantothenic acid, share this analogue relationship with isoniazid, so they are unaffected. The vitamin made deficient is therefore pyridoxine. \[\boxed{\text{Pyridoxine}}\]