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Schizoaffective disorder with recent carbamazepine exposure — DFSRH MCQ

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EasyPsychosisSchizoaffective disorder with recent carbamazepine exposureDFSRH

A 29-year-old woman with schizoaffective disorder, bipolar type, requests emergency contraception. Her mental state is stable, and she has capacity to make this decision. Carbamazepine, previously prescribed as a mood stabiliser, was stopped 14 days ago following psychiatric review. She had unprotected sexual intercourse 48 hours ago on day 10 of a regular 28-day cycle, with no other unprotected intercourse this cycle. Her BMI is 23 kg/m². After counselling, she declines a copper intrauterine device and requests oral emergency contraception. Which is the most appropriate regimen?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Give levonorgestrel 3 mg as a single dose

Explanation lettering: D = shown as C · E = shown as D · C = shown as E

Carbamazepine is a hepatic enzyme inducer, and FSRH guidance states that metabolism of both levonorgestrel and ulipristal acetate emergency contraception may remain increased for 28 days after an enzyme inducer is stopped. This patient discontinued carbamazepine only 14 days ago. The copper IUD is the preferred emergency contraceptive because enzyme induction does not affect it, but her capacitous refusal must be respected. The recommended oral alternative is therefore off-label double-dose levonorgestrel: 3 mg taken as a single dose. Its effectiveness in this setting is uncertain, which should be discussed. A is inappropriate because she remains within an effective emergency-contraception window; pregnancy testing at 21 days is follow-up rather than treatment. B is the standard levonorgestrel regimen but may provide inadequate exposure during residual enzyme induction. C is attractive because intercourse occurred near the anticipated fertile window, when ulipristal would ordinarily be preferred to standard-dose levonorgestrel; however, FSRH does not recommend ulipristal during or within 28 days after enzyme-inducer use. D provides appropriate vomiting advice for standard-dose levonorgestrel but still starts with an inadequate dose for this interaction. The entire 3 mg dose should be taken together.

Reference: FSRH Guideline: Emergency Contraception (March 2017, amended April 2026) — https://www.fsrh.org/Common/Uploaded%20files/documents/fsrh-guideline-emergency-contraception03dec2020-amendedjuly2023-11jul.pdf Levonelle 1500 microgram tablet — Summary of Product Characteristics (2 July 2021) — https://www.medicines.org.uk/emc/product/133/smpc