Contraception: enzyme-inducing drugs: practice question

A OBG 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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OBG · Contraception: enzyme-inducing drugs

Sample item

A 26-year-old with epilepsy on carbamazepine wants highly effective contraception. Which method is least affected by her drug?

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

The answer and the reasoning

D. Levonorgestrel intrauterine system or copper IUCD

Carbamazepine, phenytoin, phenobarbitone, topiramate and rifampicin induce hepatic enzymes and lower contraceptive steroid levels, so combined pills, progestogen-only pills and implants may fail. Intrauterine devices and DMPA are not affected by enzyme induction. Folic acid and contraception planning are part of preconception care in epilepsy.

Option by option

  • A. Etonogestrel implant

    Implant efficacy is reduced by enzyme inducers.

  • B. Progestogen-only pill

    The progestogen-only pill is also less effective.

  • C. Combined oral contraceptive pill

    Enzyme induction reduces COC efficacy.

  • D. Levonorgestrel intrauterine system or copper IUCD (correct)

    Correct. Intrauterine methods act locally and are unaffected.

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 OBG question

What is the answer to this OBG question?

The best answer is D, Levonorgestrel intrauterine system or copper IUCD. Carbamazepine, phenytoin, phenobarbitone, topiramate and rifampicin induce hepatic enzymes and lower contraceptive steroid levels, so combined pills, progestogen-only pills and implants may fail.

Why is "Etonogestrel implant" not the answer?

Implant efficacy is reduced by enzyme inducers.

Why is "Progestogen-only pill" not the answer?

The progestogen-only pill is also less effective.

Why is "Combined oral contraceptive pill" not the answer?

Enzyme induction reduces COC efficacy.

What concept does this question test?

It tests Contraception: enzyme-inducing drugs in OBG. Intrauterine devices and DMPA are not affected by enzyme induction. Folic acid and contraception planning are part of preconception care in epilepsy.

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 Contraception: enzyme-inducing drugs?

Learn management algorithms as steps: PPH, eclampsia, ectopic pregnancy. Then use the flashcards and the other OBG 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.