Mood stabilisers: carbamazepine hyponatraemia: practice question

A Psychiatry 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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Psychiatry · Mood stabilisers: carbamazepine hyponatraemia

Sample item

A bipolar patient on carbamazepine becomes lethargic with confusion, and serum sodium is 119 mEq per litre. The mechanism is

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

The answer and the reasoning

C. Syndrome of inappropriate ADH secretion

Carbamazepine and oxcarbazepine can cause SIADH with hyponatraemia, especially in elderly patients. Symptoms include confusion, lethargy and seizures. Management is fluid restriction, drug withdrawal or dose reduction, and correction of sodium at a controlled rate.

Option by option

  • A. Primary polydipsia from lithium

    Lithium is not part of this scenario.

  • B. Diabetes insipidus

    Diabetes insipidus causes hypernatraemia from dilute urine, as in lithium use.

  • C. Syndrome of inappropriate ADH secretion (correct)

    Correct. Carbamazepine causes SIADH.

  • D. Adrenal insufficiency from drug

    Adrenal insufficiency is not the usual mechanism.

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 Psychiatry question

What is the answer to this Psychiatry question?

The best answer is C, Syndrome of inappropriate ADH secretion. Carbamazepine and oxcarbazepine can cause SIADH with hyponatraemia, especially in elderly patients.

Why is "Primary polydipsia from lithium" not the answer?

Lithium is not part of this scenario.

Why is "Diabetes insipidus" not the answer?

Diabetes insipidus causes hypernatraemia from dilute urine, as in lithium use.

Why is "Adrenal insufficiency from drug" not the answer?

Adrenal insufficiency is not the usual mechanism.

What concept does this question test?

It tests Mood stabilisers: carbamazepine hyponatraemia in Psychiatry. Symptoms include confusion, lethargy and seizures. Management is fluid restriction, drug withdrawal or dose reduction, and correction of sodium at a controlled rate.

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 Mood stabilisers: carbamazepine hyponatraemia?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry 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.