Autonomic nervous system: sulfasalazine adverse effects: 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 · Autonomic nervous system: sulfasalazine adverse effects

Sample item

A young man with ulcerative colitis on sulfasalazine presents with infertility and a macrocytic anaemia. Semen analysis shows a low sperm count. Which statement best explains these findings?

AThe 5-aminosalicylic acid moiety causes testicular atrophyBSulfasalazine induces vitamin B12 malabsorption by blocking intrinsic factorCThe sulfapyridine moiety causes reversible oligospermia and impairs folate absorptionDDirect inhibition of testosterone synthesis by the drug

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

The answer and the reasoning

C. The sulfapyridine moiety causes reversible oligospermia and impairs folate absorption

Sulfasalazine is split by colonic bacteria into 5-aminosalicylic acid, the active anti-inflammatory part, and sulfapyridine, which causes most adverse effects. These include reversible oligospermia, folate deficiency, haemolysis in G6PD deficiency and hypersensitivity. Switching to mesalazine restores sperm counts.

Option by option

A. The 5-aminosalicylic acid moiety causes testicular atrophy
The 5-ASA part is well tolerated and does not cause oligospermia, which is why mesalazine alone is a substitute.
B. Sulfasalazine induces vitamin B12 malabsorption by blocking intrinsic factor
Sulfasalazine interferes with folate, and not with intrinsic factor or vitamin B12 absorption.
C. The sulfapyridine moiety causes reversible oligospermia and impairs folate absorption (correct)
Correct. The sulfapyridine moiety is responsible for oligospermia and folate deficiency.
D. Direct inhibition of testosterone synthesis by the drug
The effect on sperm count is reversible and is not due to an effect on testosterone synthesis.

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.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, The sulfapyridine moiety causes reversible oligospermia and impairs folate absorption. Sulfasalazine is split by colonic bacteria into 5-aminosalicylic acid, the active anti-inflammatory part, and sulfapyridine, which causes most adverse effects.

Why is "The 5-aminosalicylic acid moiety causes testicular atrophy" not the answer?

The 5-ASA part is well tolerated and does not cause oligospermia, which is why mesalazine alone is a substitute.

Why is "Sulfasalazine induces vitamin B12 malabsorption by blocking intrinsic…" not the answer?

Sulfasalazine interferes with folate, and not with intrinsic factor or vitamin B12 absorption.

Why is "Direct inhibition of testosterone synthesis by the drug" not the answer?

The effect on sperm count is reversible and is not due to an effect on testosterone synthesis.

What concept does this question test?

It tests Autonomic nervous system: sulfasalazine adverse effects in Pharmacology. These include reversible oligospermia, folate deficiency, haemolysis in G6PD deficiency and hypersensitivity. Switching to mesalazine restores sperm counts.

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 Autonomic nervous system: sulfasalazine adverse effects?

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.