Toxicology: barbiturate 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: barbiturate overdose

Sample item

A woman with phenobarbitone overdose is deeply comatose with hypothermia and blisters over pressure points. Besides airway support, which measure enhances elimination of this long-acting barbiturate?

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

The answer and the reasoning

C. Urinary alkalinisation with intravenous sodium bicarbonate

Phenobarbitone is a weak acid, so alkalinising the urine traps the ionised drug in the tubule and increases its renal excretion. Haemodialysis or charcoal haemoperfusion is used in severe cases. Skin bullae over pressure points are a recognised barbiturate sign.

Option by option

  • A. Forced diuresis with furosemide alone

    Diuresis without alkalinisation does not trap the drug and risks fluid overload.

  • B. Urinary acidification with ammonium chloride

    Acidifying the urine would reduce excretion of a weak acid.

  • C. Urinary alkalinisation with intravenous sodium bicarbonate (correct)

    Correct. Alkaline urine increases ionisation and excretion of a weak acid.

  • D. Flumazenil infusion

    Flumazenil reverses benzodiazepines and has no action on barbiturates.

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.

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Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is C, Urinary alkalinisation with intravenous sodium bicarbonate. Phenobarbitone is a weak acid, so alkalinising the urine traps the ionised drug in the tubule and increases its renal excretion.

Why is "Forced diuresis with furosemide alone" not the answer?

Diuresis without alkalinisation does not trap the drug and risks fluid overload.

Why is "Urinary acidification with ammonium chloride" not the answer?

Acidifying the urine would reduce excretion of a weak acid.

Why is "Flumazenil infusion" not the answer?

Flumazenil reverses benzodiazepines and has no action on barbiturates.

What concept does this question test?

It tests Toxicology: barbiturate overdose in Forensic Medicine. Haemodialysis or charcoal haemoperfusion is used in severe cases. Skin bullae over pressure points are a recognised barbiturate sign.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: barbiturate 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.