Phenyltriazine·Neurology - Anticonvulsants

lamOTRIGine

Prevention of depressive episodes in Bipolar I and II, focal and generalized epilepsy

PBSMOOD STABLamictal, Lamidus25 mg tabletS4+1

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At a glance

Max Dose

200-400 mg

Half-life

33 h

Caution: SJS/TEN Rash

RISK

Caution: Titration

SLOW

Cautions

Avoid / Cautions

History of Lamotrigine-induced rash. Pregnancy Category D (Historically), but modern registry data proves it is one of the SAFEST mood stabilisers in pregnancy. However, estrogen (OCP/pregnancy) rapidly clears lamotrigine, requiring the dose to be doubled or tripled to prevent seizures/relapse.

Where it stands

Rapid Summary

Overview

Broad-spectrum anticonvulsant. The absolute gold-standard mood stabiliser for Bipolar Depression. Exceptionally well tolerated long-term, but carries a terrifying risk of fatal skin detachment if started too fast.

Clinical Focus

The patient must understand that ANY rash in the first 8 weeks requires immediate cessation of the drug and ED review.

Bottom Line

Lamotrigine is a well-tolerated anticonvulsant and mood stabiliser (bipolar depression), but requires extremely slow titration to avoid life-threatening Stevens-Johnson Syndrome.

Formulation & Access

Brand Names

Lamictal, Lamidus

Oral Routes

Dispersible/Chewable tablets (25 mg, 50 mg, 100 mg, 200 mg).

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Prevention of depressive episodes in Bipolar I and II, focal and generalized epilepsy.

Clinical Place

Useless for acute mania (takes 2 months to work). The best drug available for keeping bipolar patients out of suicidal depression.

Quick reference

Class & Role

Phenyltriazine — Broad-spectrum anticonvulsant.

Route / Formulation

Dispersible/Chewable tablets (25 mg, 50 mg, 100 mg, 200 mg). (Lamictal, Lamidus)

Usual Dose & Max

Weeks 1-2: 25 mg OD. Weeks 3-4: 50 mg OD. Week 5: 100 mg OD. Target 200 mg/day. Max 200-400 mg/day (Titration MUST take 6-8 weeks).

Key Indication Doses

Bipolar Depression / Epilepsy (Standard): Weeks 1-2: 25 mg OD. Weeks 3-4: 50 mg OD. Week 5: 100 mg OD. Target 200 mg/day. With Valproate (Inhibitor): Halve the speed. 25 mg on ALTERNATE days for 2 weeks, then 25 mg daily. With Carbamazepine (Inducer): Double the speed. 50 mg daily for 2 weeks, then 100 mg daily.

Best Uses

Lamotrigine is a well-tolerated anticonvulsant and mood stabiliser (bipolar depression), but requires extremely slow titration to avoid life-threatening Stevens-Johnson Syndrome.

Key Risks

Dermatological: Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN). Risk is ~1 in 1000. Risk skyrockets if starting dose is too high, titration is too fast, or if combined with Valproate. Neurological: Dizziness, headache, ataxia, diplopia (mostly dose-related). Metabolic: Weight neutral, zero sedation, zero cognitive blunting (unlike Lithium/Valproate).

Key Interactions

Valproate heavily inhibits glucuronidation, doubling Lamotrigine levels and guaranteeing SJS. Must use the specialized 'Blue' titration pack. Carbamazepine/Phenytoin induce clearance, halving Lamotrigine levels. Must use the 'Green' pack. The combined oral contraceptive pill (COCP) halves lamotrigine blood levels. If the woman stops the pill for the placebo week, lamotrigine levels spike, causing acute neurotoxicity (ataxia/double vision).

Monitoring

Warn patient: 'If you get any rash, sore mouth, or inflamed eyes in the first two months, stop the pills and go to hospital.'. No specific routine laboratory tests required (TDM is rarely useful outside of pregnancy).

Clinical Pearl

If a patient forgets to take their Lamotrigine for 5 days in a row, they have lost their tolerance. You CANNOT restart them on 200mg. You must start from the very beginning (25mg) and spend 6 weeks titrating up again, or they will get SJS.

Access

Lamictal, Lamidus25 mg tablet

Brand: Lamictal, Lamidus
Formulation: Dispersible/Chewable tablets (25 mg, 50 mg, 100 mg, 200 mg).

From this page

No calculator, monitoring schedule or factsheet is linked to this medicine page yet.

Cautions

Avoid / Cautions