Endocrine drugs: sulfonylurea and hyponatraemia: 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 · Endocrine drugs: sulfonylurea and hyponatraemia

Sample item

A 60-year-old diabetic man on a long-acting sulfonylurea has a serum sodium of 122 mmol/L, is euvolaemic, and has concentrated urine. Which drug is most likely responsible, by potentiating the action of antidiuretic hormone?

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

The answer and the reasoning

C. Chlorpropamide

Chlorpropamide enhances the renal action of ADH and can cause a syndrome like SIADH with hyponatraemia. It also causes a disulfiram-like flush with alcohol. It is long acting and now rarely used. Other sulfonylureas do this to a much smaller degree.

Option by option

  • A. Tolbutamide

    Tolbutamide is short acting and seldom causes hyponatraemia.

  • B. Glimepiride

    Glimepiride seldom causes hyponatraemia, and its main risk is hypoglycaemia.

  • C. Chlorpropamide (correct)

    Correct. This first-generation drug potentiates ADH and can produce dilutional hyponatraemia.

  • D. Glipizide

    Glipizide rarely causes hyponatraemia and is mainly associated with hypoglycaemia.

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, Chlorpropamide. Chlorpropamide enhances the renal action of ADH and can cause a syndrome like SIADH with hyponatraemia.

Why is "Tolbutamide" not the answer?

Tolbutamide is short acting and seldom causes hyponatraemia.

Why is "Glimepiride" not the answer?

Glimepiride seldom causes hyponatraemia, and its main risk is hypoglycaemia.

Why is "Glipizide" not the answer?

Glipizide rarely causes hyponatraemia and is mainly associated with hypoglycaemia.

What concept does this question test?

It tests Endocrine drugs: sulfonylurea and hyponatraemia in Pharmacology. It also causes a disulfiram-like flush with alcohol. It is long acting and now rarely used. Other sulfonylureas do this to a much smaller degree.

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 Endocrine drugs: sulfonylurea and hyponatraemia?

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.