Leflunomide Teratogenicity — SCE Rheumatology MCQ
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Correct answer: B — Stop leflunomide and start a colestyramine washout immediately
Explanation lettering: C = shown as B · B = shown as C · E = shown as D · D = shown as E
Leflunomide must be stopped and an accelerated drug-elimination (washout) procedure started immediately. Its active metabolite A771726 (teriflunomide) undergoes enterohepatic recirculation and can persist at teratogenic plasma levels for up to two years, so simply stopping and awaiting natural elimination (A) is inadequate once conception has occurred. The UK SmPC specifies colestyramine 8 g three times daily for 11 days (activated charcoal 50 g four times daily is an alternative), with two plasma A771726 levels <0.02 mg/L measured at least 14 days apart to confirm adequate elimination. Sulfasalazine (B) is pregnancy-compatible and may later be used for disease control, but it does not remove the persisting metabolite and is not the immediate priority. Continuing leflunomide (D) is contraindicated in pregnancy. Inadvertent exposure does not itself mandate termination (E); the patient should receive urgent washout, counselling and specialist obstetric/fetal-medicine review.
Reference: Electronic Medicines Compendium. Leflunomide 10mg film-coated tablets — Summary of Product Characteristics, sections 4.4/4.6 (pregnancy and accelerated elimination/washout procedure). https://www.medicines.org.uk/emc/product/5395/smpc