Antiepileptic — Focal Seizures / Trigeminal Neuralgia / Bipolar Disorder Pregnancy: Avoid — significant teratogen (neural tube defects, craniofacial anomalies, cognitive effects); folic acid 5 mg/day pre-conception; vitamin K 10 mg/day last month; register with UK Epilepsy and Pregnancy Register

Carbamazepine (Paediatric)

Brand names: Tegretol, Tegretol Retard, Carbagen SR

Adult dose

Dose: Epilepsy: 100–200 mg once or twice daily initially; increase slowly to 400–800 mg twice daily; Trigeminal neuralgia: 100 mg twice daily initially

Route: Oral

Frequency: Twice daily (modified-release preferred)

Max: 1.6–2 g/day

Adult reference — see paediatric dose section

Paediatric dose

Dose: Initial: 5 mg/kg/day; increase by 2.5–5 mg/kg every 1–2 weeks mg/kg

Route: Oral (liquid 100 mg/5 mL, suppositories, or tablets — modified-release preferred for compliance)

Frequency: Twice daily (modified-release) or 3 times daily (immediate-release)

Max: Under 5 years: 200–400 mg/day; 5–10 years: 400–600 mg/day; over 10 years: 0.8–1 g/day

BNFc: liquid (100 mg/5 mL) useful in young children. Modified-release tablets reduce peak-trough variability and improve tolerability. Autoinduction of CYP3A4 occurs over first 3–4 weeks — plasma levels fall after starting; recheck levels and adjust dose. AVOID in absence seizures or myoclonic epilepsy — may worsen these seizure types. HLA-B*1502 screening before starting (Asian patients) — SJS/TEN risk.

Dose adjustments

Renal

No dose adjustment required; active metabolite (carbamazepine-10,11-epoxide) may accumulate — monitor levels

Hepatic

Use with caution — hepatically metabolised; reduce dose in significant hepatic impairment; monitor LFTs

Paediatric weight-based calculator

Patient weight (kg)

Clinical pearls

HLA-B*1502 pharmacogenomic screening: MHRA recommends testing all patients of Han Chinese, Thai, and other Asian ancestry before starting — HLA-B*1502 strongly associated with carbamazepine-induced SJS/TEN (relative risk 80×); do not start if positive unless benefit clearly outweighs risk
Autoinduction: carbamazepine induces its own metabolism over first 3–4 weeks — serum levels fall; titrate slowly and recheck levels at 4–6 weeks; final therapeutic level 4–12 mg/L
Hyponatraemia (SIADH): common, particularly in elderly but occurs in children too — check sodium at baseline and 3-monthly; can precipitate seizures paradoxically (hyponatraemia lowers seizure threshold)
OCP failure: carbamazepine accelerates oestrogen and progesterone metabolism — women on combined OCP need higher-dose pill (≥50 mcg oestrogen) or alternative contraception (IUCD, Depo-Provera)

Contraindications

Absence or myoclonic epilepsy
Bone marrow depression
Concurrent MAOIs or within 2 weeks
AV block
HLA-B*1502 carriers (Asian ancestry) — high SJS/TEN risk

Side effects

Drowsiness, dizziness, ataxia (especially at initiation)
Diplopia (dose-related)
Hyponatraemia (SIADH)
Aplastic anaemia (rare — monitor FBC)
Hepatotoxicity (rare)
SJS/TEN (HLA-B*1502 — Asian populations)
Rash (10%)
Teratogenicity

Interactions

Strong CYP3A4 inducer — reduces levels of many drugs: oral contraceptives (OCP failure), valproate, lamotrigine, phenytoin, warfarin, ciclosporin, antipsychotics
Macrolides (erythromycin, clarithromycin) — increase carbamazepine to toxic levels (CYP3A4 inhibition)
Valproate — increases toxic epoxide metabolite levels
Lamotrigine — carbamazepine increases lamotrigine clearance (halve lamotrigine dose)

Monitoring

Carbamazepine serum levels (target 4–12 mg/L — check trough)
Sodium (SIADH)
FBC (aplastic anaemia — check before and 6-monthly)
LFTs
HLA-B*1502 (Asian patients before initiation)
Height and weight (growth)

Reference: BNF for Children; MHRA HLA-B*1502 Safety Update 2008; NICE NG217 (Epilepsy); BNFc; Cochrane Review AEDs in Pregnancy. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways