Carbamazepine

Dibenzazepine·Neurology - Anticonvulsants

Focal (partial) seizures, generalized tonic-clonic seizures, trigeminal neuralgia, bipolar disorder

PBSMOOD STABTegretol, Tegretol CR, Teril200 mg tabletS4+1

Target Range

17–42 umol/L

Half-life

15 h (Auto-inducer)

CYP Inducer

POTENT

SJS/TEN

HLA-B*1502

Rapid Summary

Overview

Broad-spectrum anticonvulsant. A notoriously difficult drug to manage due to auto-induction (it speeds up its own liver metabolism over time) and catastrophic drug interactions.

Maximum Dose

Max 2000 mg/day (Titrated via TDM).

Clinical Focus

One of the most potent CYP450 inducers in human medicine. It will completely obliterate the blood levels of Oral Contraceptives, DOACs, and Antipsychotics.

Bottom Line

Carbamazepine is an anticonvulsant and mood stabiliser for focal seizures and trigeminal neuralgia, but is a potent CYP inducer with extensive drug interactions and requires HLA-B*15:02 testing in at-risk populations.

Formulation & Access

Brand Names

Tegretol, Tegretol CR, Teril

Oral Routes

Tablets IR (100, 200 mg). CR Tablets (200, 400 mg). Oral liquid.

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Focal (partial) seizures, generalized tonic-clonic seizures, trigeminal neuralgia, bipolar disorder.

Clinical Place

Gold standard for Trigeminal Neuralgia. Increasingly avoided for epilepsy due to newer, safer drugs (Levetiracetam) lacking enzyme interactions.

Quick reference

Class & Role

Dibenzazepine — Broad-spectrum anticonvulsant.

Route / Formulation

Tablets IR (100, 200 mg). CR Tablets (200, 400 mg). Oral liquid. (Tegretol, Tegretol CR, Teril)

Usual Dose & Max

Start PO 100-200 mg BD. Titrate slowly to target 400-1000 mg BD (Requires Controlled Release formulation for BD dosing). Max 2000 mg/day (Titrated via TDM).

Key Indication Doses

Epilepsy: Start PO 100-200 mg BD. Titrate slowly to target 400-1000 mg BD (Requires Controlled Release formulation for BD dosing). Trigeminal Neuralgia: PO 100 mg BD. Titrate to response (Often provides miraculous pain relief). Bipolar Mania: PO 200-400 mg/day in divided doses.

Best Uses

Avoid / Cautions

Prior bone marrow depression, concurrent MAOIs, AV heart block. Pregnancy Category D (Spina bifida, craniofacial defects).

Key Risks

Dermatological: Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN). Massive risk in patients of Asian descent carrying the HLA-B*1502 allele. Haematological: Agranulocytosis, aplastic anemia (Rare but fatal). Metabolic: Hyponatremia (SIADH), though less common than with Oxcarbazepine. Neurological: Dizziness, ataxia, diplopia (double vision).

Key Interactions

Massively induces CYP3A4, CYP1A2, and CYP2C9. Destroys efficacy of DOACs (Apixaban/Rivaroxaban), Warfarin, Oral Contraceptives, Clozapine, Quetiapine, and Macrolides. A nightmare for polypharmacy. Valproate pushes Carbamazepine off proteins and inhibits its breakdown, causing a massive spike in the toxic active metabolite (carbamazepine-10,11-epoxide).

Monitoring

TDM (Target: 17-42 umol/L). Must check FBC (for marrow suppression), U&E (sodium), and LFTs at baseline and periodically. Stop the drug instantly and go to ED if ANY skin rash, mouth ulcers, or severe sore throat develops.

Clinical Pearl

You prescribe a patient 200mg BD. In week 2, their seizures stop and their blood levels are perfect. In week 4, the seizures return. The drug has forced the liver to build more enzymes, digesting the drug twice as fast. You MUST re-check levels at 4 weeks and increase the dose.

Access

Tegretol, Tegretol CR, Teril200 mg tablet

Brand: Tegretol, Tegretol CR, Teril
Formulation: Tablets IR (100, 200 mg)