Thyroid drugs: antithyroid toxicity: 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 · Thyroid drugs: antithyroid toxicity

Sample item

A woman on carbimazole for five weeks for Graves disease develops fever and sore throat. What should be done first?

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

The answer and the reasoning

A. Stop carbimazole and urgently obtain a total and differential leucocyte count

Agranulocytosis is a rare, idiosyncratic and serious adverse effect of thionamides that typically occurs in the first 3 months. Patients are advised to report fever or sore throat at once, the drug must be stopped, and a white count with neutrophil count obtained. Cross-sensitivity between carbimazole and propylthiouracil means switching is not recommended.

Option by option

  • A. Stop carbimazole and urgently obtain a total and differential leucocyte count (correct)

    Correct. Stop the offending drug and confirm neutropenia with a blood count.

  • B. Add oral prednisolone and continue the drug

    Steroids do not reverse drug-induced agranulocytosis and the drug must be stopped.

  • C. Switch to propylthiouracil immediately

    There is cross-reactivity between thionamides, so propylthiouracil is not a safe substitute.

  • D. Continue carbimazole and give oral antibiotics

    Continuing the drug during possible agranulocytosis risks fatal sepsis.

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 A, Stop carbimazole and urgently obtain a total and differential leucocyte count. Agranulocytosis is a rare, idiosyncratic and serious adverse effect of thionamides that typically occurs in the first 3 months.

Why is "Add oral prednisolone and continue the drug" not the answer?

Steroids do not reverse drug-induced agranulocytosis and the drug must be stopped.

Why is "Switch to propylthiouracil immediately" not the answer?

There is cross-reactivity between thionamides, so propylthiouracil is not a safe substitute.

Why is "Continue carbimazole and give oral antibiotics" not the answer?

Continuing the drug during possible agranulocytosis risks fatal sepsis.

What concept does this question test?

It tests Thyroid drugs: antithyroid toxicity in Pharmacology. Patients are advised to report fever or sore throat at once, the drug must be stopped, and a white count with neutrophil count obtained. Cross-sensitivity between carbimazole and propylthiouracil means switching is not recommended.

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 Thyroid drugs: antithyroid toxicity?

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.