Lamotrigine (Psychiatric Use)

How it works

Lamotrigine inhibits voltage-gated sodium channels and stabilises neuronal membranes, modulating release of excitatory neurotransmitters, which is thought to underpin its mood-stabilising effect.

Prescribing in practice

• Serious skin reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis can occur, so the dose must be titrated slowly from a low starting dose and any rash, especially with systemic or mucosal involvement, prompts urgent review and usually withdrawal.
• Rapid escalation and interactions markedly affect risk: valproate raises lamotrigine levels (slower titration needed) while enzyme inducers and some hormonal contraceptives lower them, requiring dose adjustment.
• Counsel on hypersensitivity syndrome and the need to seek help for fever, swelling or blistering, and re-titrate from low dose if treatment has been interrupted.

Monitoring

Monitor for skin reactions and hypersensitivity, mood response and the impact of interacting drugs and any treatment interruption on dosing.

Counselling the patient

• Report any rash, blistering, mouth ulcers or fever urgently, particularly in the first weeks.
• Take exactly as titrated and never increase the dose faster than instructed.
• Tell your clinician about contraceptive changes, as these can alter the dose needed.

Evidence & guidelines

NICE bipolar disorder guidance supports lamotrigine for preventing bipolar depression, and product information emphasises slow titration to reduce serious rash risk.