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Anticonvulsant (Sodium Channel Blocker)

Lamotrigine

Brand names: Lamictal

Lamotrigine is an antiepileptic used for focal and generalised seizures and as a mood stabiliser in bipolar disorder.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Dosing is based on concomitant medications, indication, and patient age. ( 2.1 , 2.2 , 2.3 , 2.4 ) To avoid an increased risk of rash, the recommended initial dose and subsequent dose escalations should not be exceeded. Lamotrigine Orally Disintegrating Tablets Patient Titration Kits are available for the first 5 weeks of treatment. ( 2.1 , 16 ) Do not restart lamotrigine orally disintegrating tablets in patients who discontinued due to rash unless the potential benefits clearly outweigh the risks. ( 2.1 , 5.1 ) Adjustments to maintenance doses will be necessary in most patients starting or stopping estrogen-containing products, including oral contraceptives. ( 2.1 , 5.9 ) Discontinuation: …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-04-22. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It stabilises neuronal membranes mainly by blocking voltage-gated sodium channels, reducing excitatory neurotransmitter release.

Prescribing in practice

  • Serious rashes (including Stevens-Johnson syndrome) can occur, especially with rapid escalation or when combined with valproate — titrate slowly and stop for any significant rash.
  • Valproate markedly raises lamotrigine levels (use a lower lamotrigine dose); enzyme inducers lower them.
  • Do not stop abruptly; levels may fall in pregnancy and need review.

Monitoring

Watch for rash during titration; review seizure/mood control; consider levels around pregnancy.

Counselling the patient

  • Increase the dose slowly, exactly as instructed.
  • Report any rash immediately, particularly in the first weeks.
  • Do not stop suddenly.

Evidence & guidelines

A first-line option for focal epilepsy and some generalised seizures, and a maintenance treatment in bipolar depression, with a key rash/titration caution.

Reference: NICE NG217; Lamictal SPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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