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Emergency contraception following recent hepatic enzyme-inducer use — DFSRH MCQ

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EasyFSRHEmergency contraception following recent hepatic enzyme-inducer useDFSRH

A 29-year-old woman requests emergency contraception 40 hours after a condom split. This occurred on day 11 of a regular 28-day cycle, with no other unprotected sexual intercourse during the cycle. She completed a 6-month course of rifampicin 14 days ago. Her BMI is 23 kg/m², and she is not using hormonal contraception. A copper intrauterine device is clinically suitable and has been offered, but she declines insertion after counselling. Which oral emergency contraception regimen is most appropriate?

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

Reveal the answer and explanation

Correct answer: A — Levonorgestrel 3 mg orally as a single dose now

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

Rifampicin induces hepatic drug-metabolising enzymes, and this interaction remains clinically relevant for 28 days after stopping treatment. Consequently, exposure to both levonorgestrel and ulipristal acetate may be reduced. The timing of intercourse near estimated ovulation would ordinarily favour ulipristal over levonorgestrel, but recent enzyme induction overrides that preference. The copper IUD is unaffected and should be offered first; because it has been declined, FSRH recommends considering off-label levonorgestrel 3 mg taken together, with counselling that its effectiveness in this setting is uncertain. Ulipristal 30 mg (B) is normally favoured for intercourse in the five days before estimated ovulation, but it is not recommended during or within 28 days after enzyme-inducer use. Standard-dose levonorgestrel 1.5 mg (C) does not compensate for increased metabolism. Doubling ulipristal to 60 mg (D) is not recommended because effectiveness and safety have not been established for this strategy. Dividing levonorgestrel 3 mg over 12 hours (E) is not the recommended dose-escalation regimen: the two 1.5 mg tablets should be taken together. She should also receive advice regarding further pregnancy risk, ongoing contraception and pregnancy testing 21 days after the episode.

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 (28 July 2021) — https://www.medicines.org.uk/emc/product/133/smpc