Emergency contraception after recent rifampicin exposure — DFSRH MCQ

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EasyAntibioticsEmergency contraception after recent rifampicin exposureDFSRH

A 31-year-old woman requests emergency contraception 48 hours after a condom split. She has regular 28-day cycles; her last menstrual period began 12 days ago. She completed rifampicin-containing treatment 14 days ago and takes no other medication. After counselling, she declines a copper intrauterine device despite being medically eligible. Which oral emergency contraceptive regimen is most appropriate?

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

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

Rifampicin induces CYP3A4, increasing the metabolism of both levonorgestrel and ulipristal acetate. FSRH guidance treats this interaction as clinically relevant during enzyme-inducer use and for 28 days after cessation. This woman stopped rifampicin only 14 days ago, so recent enzyme induction remains the decisive discriminator. A copper IUD is preferred because its efficacy is unaffected by enzyme induction, but she has declined it. The recommended oral alternative is therefore levonorgestrel 3 mg taken as one administration, although she should be counselled that effectiveness in this setting is uncertain. A is the standard levonorgestrel regimen but may provide inadequate exposure after recent rifampicin. B gives the required total dose but uses an unsupported divided schedule; both 1.5 mg tablets should be taken together. D would otherwise be attractive because intercourse occurred near estimated ovulation, but ulipristal is not recommended within four weeks of enzyme-inducer exposure. E incorrectly extrapolates the levonorgestrel dose-doubling strategy to ulipristal; FSRH advises that double-dose ulipristal is not recommended because supporting efficacy data are absent. Oral emergency contraception should be administered promptly, with advice regarding ongoing contraception and pregnancy testing 21 days after the condom failure.

Reference: FSRH Guideline: Emergency Contraception (Amended April 2026) — https://www.fsrh.org/Common/Uploaded%20files/documents/fsrh-guideline-emergency-contraception03dec2020-amendedjuly2023-11jul.pdf Levonorgestrel 1.5 mg Tablets: Summary of Product Characteristics (September 2021) — https://www.medicines.org.uk/emc/product/7308/smpc Ulipristal 30 mg film-coated tablets: Summary of Product Characteristics (24 July 2023) — https://www.medicines.org.uk/emc/product/14200/smpc