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Bipolar disorder treated with lamotrigine — DFSRH MCQ

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EasyMental HealthBipolar disorder treated with lamotrigineDFSRH

A 34-year-old woman with bipolar disorder has remained euthymic for 3 years while taking lamotrigine 300 mg daily. Her current dose was established after she started a continuous combined oral contraceptive containing ethinylestradiol and levonorgestrel. She takes no enzyme-inducing medication. During the past month, she has had two episodes of a gradually enlarging scintillating scotoma lasting 20 minutes, followed by unilateral headache and photophobia. She has taken her contraceptive correctly, and pregnancy is reasonably excluded. She now requests hormone-free, highly effective contraception and would accept a copper intrauterine device. There are no contraindications to insertion. Which is the most appropriate management?

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Correct answer: A — Stop the combined oral contraceptive, insert the copper intrauterine device, and coordinate prompt review of lamotrigine dosing and monitoring

Her focal visual symptoms followed by headache are characteristic of migraine with aura. Combined hormonal contraception is UKMEC 4 in migraine with aura because the method is associated with an unacceptable additional risk of ischaemic stroke; it should therefore be stopped rather than continued pending routine review. However, contraceptive switching cannot be considered independently of her mood stabiliser. Ethinylestradiol induces lamotrigine glucuronidation and can approximately double its clearance. When the combined contraceptive is stopped, lamotrigine clearance may fall substantially and serum concentrations can rise, causing dose-related toxicity such as dizziness, diplopia or ataxia. FSRH therefore advises consultation with the patient's GP, neurologist or psychiatrist when hormonal contraception is started or stopped so that monitoring and individualised dose adjustment can be arranged. A copper intrauterine device provides effective hormone-free contraception and is not affected by lamotrigine. A is inappropriate because migraine with aura precludes continued combined hormonal contraception. C overlooks the predictable rise in lamotrigine exposure after oestrogen withdrawal. D provides an effective contraceptive option but similarly fails to address the lamotrigine interaction. E recognises that a dose reduction may be required, but an automatic immediate 50% reduction risks loss of mood stability; the manufacturer recommends a gradual, clinically guided adjustment rather than an unplanned empirical change.

Reference: FSRH Guideline: Combined Hormonal Contraception (October 2023) — https://www.fsrh.org/Common/Uploaded%20files/documents/fsrh-guideline-combined-hormonal-contraception-october-2023.pdf FSRH Drug Interactions with Hormonal Contraception (May 2022) — https://www.fsrh.org/Common/Uploaded%20files/documents/drug-interactions-with-hormonal-contraception-5may2022.pdf Lamotrigine Milpharm 50 mg tablets Summary of Product Characteristics (19 May 2026) — https://www.medicines.org.uk/emc/product/4737/smpc