Antimicrobials: cephalosporin 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 · Antimicrobials: cephalosporin adverse effects

Sample item

A patient on cefoperazone for biliary sepsis develops spontaneous bruising with a raised prothrombin time, and later flushing and palpitations after drinking alcohol. Which structural feature is responsible?

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

The answer and the reasoning

D. N-methylthiotetrazole side chain

Cephalosporins such as cefoperazone, cefotetan and cefamandole contain an N-methylthiotetrazole group that inhibits vitamin K epoxide reductase and aldehyde dehydrogenase, causing hypoprothrombinaemia and a disulfiram-like reaction.

Option by option

  • A. Carboxylic acid group

    A carboxyl group is not the cause.

  • B. Aminothiazole ring

    The aminothiazole ring is not the cause.

  • C. Beta-lactam ring

    The beta-lactam ring is common to all and not specific.

  • D. N-methylthiotetrazole side chain (correct)

    Correct. The NMTT side chain explains both effects.

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 D, N-methylthiotetrazole side chain. Cephalosporins such as cefoperazone, cefotetan and cefamandole contain an N-methylthiotetrazole group that inhibits vitamin K epoxide reductase and aldehyde dehydrogenase, causing hypoprothrombinaemia and a disulfiram-like reaction.

Why is "Carboxylic acid group" not the answer?

A carboxyl group is not the cause.

Why is "Aminothiazole ring" not the answer?

The aminothiazole ring is not the cause.

Why is "Beta-lactam ring" not the answer?

The beta-lactam ring is common to all and not specific.

What concept does this question test?

It tests Antimicrobials: cephalosporin adverse effects in Pharmacology. The correct option holds because: Correct. The NMTT side chain explains both effects.

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 Antimicrobials: cephalosporin 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.