Neurology: lamotrigine rash risk: practice question

A General Medicine 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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General Medicine · Neurology: lamotrigine rash risk

Sample item

A 28-year-old woman started lamotrigine 100 mg daily on top of sodium valproate. Ten days later she has fever, mucosal ulceration and a widespread rash with skin detachment. Which factor most increased this risk?

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

The answer and the reasoning

B. Fast titration with valproate co-therapy

Valproate inhibits lamotrigine glucuronidation and roughly doubles its half-life, and rapid dose escalation raises the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis. Lamotrigine must be started low and titrated slowly, with half doses when combined with valproate.

Option by option

  • A. Concurrent carbamazepine as an enzyme inducer

    Carbamazepine induces lamotrigine metabolism and lowers its levels.

  • B. Fast titration with valproate co-therapy (correct)

    Correct. High exposure from fast titration and valproate raises the rash risk.

  • C. Taking the drug on an empty stomach

    Food intake does not affect the risk of this reaction.

  • D. Carriage of HLA-B*15:02

    HLA-B*15:02 is linked to carbamazepine reactions in some Asian populations.

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.

More General Medicine questions

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is B, Fast titration with valproate co-therapy. Valproate inhibits lamotrigine glucuronidation and roughly doubles its half-life, and rapid dose escalation raises the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis.

Why is "Concurrent carbamazepine as an enzyme inducer" not the answer?

Carbamazepine induces lamotrigine metabolism and lowers its levels.

Why is "Taking the drug on an empty stomach" not the answer?

Food intake does not affect the risk of this reaction.

Why is "Carriage of HLA-B*15:02" not the answer?

HLA-B*15:02 is linked to carbamazepine reactions in some Asian populations.

What concept does this question test?

It tests Neurology: lamotrigine rash risk in General Medicine. Lamotrigine must be started low and titrated slowly, with half doses when combined with valproate.

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 Neurology: lamotrigine rash risk?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.