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Lamotrigine – Slow Titration to Prevent SJS — SCE Neurology MCQ

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ModerateEpilepsy & Seizure DisordersLamotrigine – Slow Titration to Prevent SJSSCE Neurology

A 45-year-old man with epilepsy presents with a severe skin reaction 2 weeks after starting lamotrigine. He was started on 100 mg daily (the standard starting dose without valproate co-prescription is 25 mg daily for the first 2 weeks). His neurologist realises the dose was escalated too quickly. Why does rapid lamotrigine titration increase the risk of severe cutaneous adverse reactions?

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Correct answer: D — Rapid lamotrigine titration overwhelms the immune tolerance mechanisms — slow introduction allows the immune system to develop tolerance to the drug, whereas rapid introduction increases the risk of hypersensitivity reactions including SJS/TEN

The risk of SJS/TEN with lamotrigine is directly related to the speed of dose titration. Starting at 25 mg daily (or 25 mg on alternate days if on valproate) and increasing slowly over 6–8 weeks allows gradual immune tolerance. Starting at higher doses or escalating too quickly significantly increases the risk of severe hypersensitivity. This is why strict titration schedules are mandated in the BNF and SmPC. The co-prescription of valproate (which doubles lamotrigine levels) further increases the risk if the lamotrigine dose is not halved. A: Titration speed is a major risk factor. C: The mechanism is immunological, not pharmacokinetic skin accumulation. D: Dose/titration speed matters significantly. E: The titration rate is the critical factor.

Reference: BNF – Lamotrigine Titration Schedule; NICE NG217; Lamotrigine SmPC