Psychopharmacology: lamotrigine and oestrogen contraceptives: practice question

A Psychiatry 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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Psychiatry · Psychopharmacology: lamotrigine and oestrogen contraceptives

Sample item

A woman with bipolar disorder is stable on lamotrigine. After starting a combined oral contraceptive pill she has a breakthrough depressive relapse. What is the likely pharmacokinetic explanation?

AEthinyloestradiol induces glucuronidation and lowers lamotrigine levelsBThe pill inhibits glucuronidation and raises lamotrigine levelsCThe pill blocks gastric absorption of lamotrigineDThe pill displaces lamotrigine from plasma proteins

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

The answer and the reasoning

A. Ethinyloestradiol induces glucuronidation and lowers lamotrigine levels

Lamotrigine is cleared by glucuronidation, which oestrogen-containing contraceptives induce, so plasma levels can fall by about half. The dose may need to be increased, and decreased again when the pill is stopped.

Option by option

A. Ethinyloestradiol induces glucuronidation and lowers lamotrigine levels (correct)
Correct. Enzyme induction by the oestrogen lowers lamotrigine and may allow relapse.
B. The pill inhibits glucuronidation and raises lamotrigine levels
Inhibition would raise levels and bring toxicity, not relapse.
C. The pill blocks gastric absorption of lamotrigine
The pill has no effect on gastric absorption of lamotrigine.
D. The pill displaces lamotrigine from plasma proteins
Protein displacement is not the known interaction of the pill with lamotrigine.

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 Psychiatry question

What is the answer to this Psychiatry question?

The best answer is A, Ethinyloestradiol induces glucuronidation and lowers lamotrigine levels. Lamotrigine is cleared by glucuronidation, which oestrogen-containing contraceptives induce, so plasma levels can fall by about half.

Why is "The pill inhibits glucuronidation and raises lamotrigine levels" not the answer?

Inhibition would raise levels and bring toxicity, not relapse.

Why is "The pill blocks gastric absorption of lamotrigine" not the answer?

The pill has no effect on gastric absorption of lamotrigine.

Why is "The pill displaces lamotrigine from plasma proteins" not the answer?

Protein displacement is not the known interaction of the pill with lamotrigine.

What concept does this question test?

It tests Psychopharmacology: lamotrigine and oestrogen contraceptives in Psychiatry. The dose may need to be increased, and decreased again when the pill is stopped.

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 Psychopharmacology: lamotrigine and oestrogen contraceptives?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry 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.