Question:
Treatment with INH (isoniazid) leads to deficiency of which vitamin?
Treatment with INH (isoniazid) leads to deficiency of which vitamin?
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INH mimics vitamin B6 and triggers a neuropathy unless that vitamin is replaced.
Updated On: Jun 24, 2026
- Thiamine
- Niacin
- Pyridoxine
- Pantothenic acid
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Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Step 1: Recall isoniazid pharmacology. INH is structurally related to pyridoxine (vitamin B6) and interferes with its metabolism.
Step 2: INH increases urinary excretion of pyridoxine and inhibits the enzyme pyridoxine phosphokinase, reducing active pyridoxal phosphate. This produces a functional B6 deficiency.
Step 3: Clinical consequence. The resulting deficiency causes peripheral neuropathy, which is why pyridoxine is co-administered with INH, especially in malnourished patients, diabetics, alcoholics and pregnant women.
Step 4: The other vitamins listed (thiamine, niacin, pantothenic acid) are not depleted by INH. Hence the answer is pyridoxine, option C.
Step 2: INH increases urinary excretion of pyridoxine and inhibits the enzyme pyridoxine phosphokinase, reducing active pyridoxal phosphate. This produces a functional B6 deficiency.
Step 3: Clinical consequence. The resulting deficiency causes peripheral neuropathy, which is why pyridoxine is co-administered with INH, especially in malnourished patients, diabetics, alcoholics and pregnant women.
Step 4: The other vitamins listed (thiamine, niacin, pantothenic acid) are not depleted by INH. Hence the answer is pyridoxine, option C.
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