Toxicology: isoniazid overdose: practice question

A Forensic Medicine 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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Forensic Medicine · Toxicology: isoniazid overdose

Sample item

A young woman who swallowed a large number of antituberculosis tablets in a suicide attempt is brought with repeated generalised seizures that do not respond to diazepam, and metabolic acidosis. Which antidote is specific?

APhysostigmineBNaloxoneCFlumazenilDPyridoxine

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

The answer and the reasoning

D. Pyridoxine

Isoniazid overdose depletes pyridoxine and reduces brain GABA, causing refractory seizures and acidosis. Intravenous pyridoxine, in a dose matching the ingested isoniazid, is the specific antidote, with benzodiazepines as adjuncts. Naloxone, flumazenil and physostigmine do not act on this mechanism.

Option by option

A. Physostigmine
Physostigmine reverses anticholinergic toxicity and may itself cause seizures.
B. Naloxone
Naloxone reverses opioid effects only.
C. Flumazenil
Flumazenil reverses benzodiazepines and does not treat isoniazid seizures.
D. Pyridoxine (correct)
Correct. Pyridoxine restores GABA synthesis and stops isoniazid-induced seizures.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is D, Pyridoxine. Isoniazid overdose depletes pyridoxine and reduces brain GABA, causing refractory seizures and acidosis.

Why is "Physostigmine" not the answer?

Physostigmine reverses anticholinergic toxicity and may itself cause seizures.

Why is "Naloxone" not the answer?

Naloxone reverses opioid effects only.

Why is "Flumazenil" not the answer?

Flumazenil reverses benzodiazepines and does not treat isoniazid seizures.

What concept does this question test?

It tests Toxicology: isoniazid overdose in Forensic Medicine. Intravenous pyridoxine, in a dose matching the ingested isoniazid, is the specific antidote, with benzodiazepines as adjuncts. Naloxone, flumazenil and physostigmine do not act on this mechanism.

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 Toxicology: isoniazid overdose?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.