Antitubercular drugs: isoniazid neuropathy: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Antitubercular drugs: isoniazid neuropathy

Sample item

A 45-year-old malnourished alcoholic man on a standard antitubercular regimen without pyridoxine develops burning paraesthesia in both feet in the second month. What is the best management?

AAdd thiamine alone and stop isoniazidBAdd pyridoxine and continue isoniazidCAdd vitamin B12 and stop the whole regimenDStop isoniazid permanently and replace it with streptomycin

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Add pyridoxine and continue isoniazid

Isoniazid forms a hydrazone with pyridoxal and increases pyridoxine excretion, which causes peripheral neuropathy, especially in slow acetylators, alcoholics, malnourished patients and diabetics. Pyridoxine supplementation prevents and treats it, so the effective drug can be continued. Stopping the whole regimen risks treatment failure.

Option by option

A. Add thiamine alone and stop isoniazid
Thiamine does not address the isoniazid-related deficiency, and stopping the drug is unnecessary.
B. Add pyridoxine and continue isoniazid (correct)
Correct. Replacing pyridoxine reverses the neuropathy while retaining a core drug.
C. Add vitamin B12 and stop the whole regimen
Stopping the entire regimen is unwarranted, and B12 is not the relevant vitamin.
D. Stop isoniazid permanently and replace it with streptomycin
Isoniazid is a key bactericidal drug and need not be stopped for a manageable neuropathy.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Add pyridoxine and continue isoniazid. Isoniazid forms a hydrazone with pyridoxal and increases pyridoxine excretion, which causes peripheral neuropathy, especially in slow acetylators, alcoholics, malnourished patients and diabetics.

Why is "Add thiamine alone and stop isoniazid" not the answer?

Thiamine does not address the isoniazid-related deficiency, and stopping the drug is unnecessary.

Why is "Add vitamin B12 and stop the whole regimen" not the answer?

Stopping the entire regimen is unwarranted, and B12 is not the relevant vitamin.

Why is "Stop isoniazid permanently and replace it with streptomycin" not the answer?

Isoniazid is a key bactericidal drug and need not be stopped for a manageable neuropathy.

What concept does this question test?

It tests Antitubercular drugs: isoniazid neuropathy in Pharmacology. Pyridoxine supplementation prevents and treats it, so the effective drug can be continued. Stopping the whole regimen risks treatment failure.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Antitubercular drugs: isoniazid neuropathy?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.