Toxicology: tricyclic antidepressants: 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 · Toxicology: tricyclic antidepressants

Sample item

A 22-year-old woman who took amitriptyline tablets has a Glasgow Coma Scale score of 9, blood pressure 80/50 mmHg, dilated pupils and a QRS of 140 ms. Which treatment is first-line for the cardiac toxicity?

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

The answer and the reasoning

C. Intravenous sodium bicarbonate

Tricyclics block cardiac fast sodium channels, widening the QRS and causing hypotension and ventricular arrhythmias, as well as anticholinergic and alpha-blocking effects. Sodium bicarbonate raises serum sodium and pH, which reverses sodium channel blockade and narrows the QRS. Class III and class IA antiarrhythmics worsen conduction.

Option by option

  • A. Physostigmine

    Physostigmine can cause seizures and asystole in tricyclic overdose.

  • B. Intravenous amiodarone

    Amiodarone prolongs conduction and can worsen arrhythmia in this setting.

  • C. Intravenous sodium bicarbonate (correct)

    Bicarbonate reverses sodium channel blockade and narrows the QRS.

  • D. Flumazenil

    Flumazenil lowers seizure threshold and does not treat sodium channel toxicity.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Intravenous sodium bicarbonate. Tricyclics block cardiac fast sodium channels, widening the QRS and causing hypotension and ventricular arrhythmias, as well as anticholinergic and alpha-blocking effects.

Why is "Physostigmine" not the answer?

Physostigmine can cause seizures and asystole in tricyclic overdose.

Why is "Intravenous amiodarone" not the answer?

Amiodarone prolongs conduction and can worsen arrhythmia in this setting.

Why is "Flumazenil" not the answer?

Flumazenil lowers seizure threshold and does not treat sodium channel toxicity.

What concept does this question test?

It tests Toxicology: tricyclic antidepressants in Pharmacology. Sodium bicarbonate raises serum sodium and pH, which reverses sodium channel blockade and narrows the QRS. Class III and class IA antiarrhythmics worsen conduction.

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: tricyclic antidepressants?

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.