Antiepileptic / Trigeminal neuralgia Pregnancy: Carbamazepine crosses the placenta and is associated with an increased risk of major congenital malformations (a meta-analysis showed 4.93% of children exposed to monotherapy in the first trimester, vs a background rate of ~2-3%), including neural tube defects (spina bifida), craniofacial defects (cleft lip/palate), cardiovascular malformations and hypospadias. Neurodevelopmental disorders have also been reported. Specialist advice, monotherapy where possible, and specialised antenatal surveillance are recommended; sudden discontinuation of AED therapy should be avoided.

Carbamazepine

Brand names: Tegretol, Carbagen

Used in: Seizures & Epilepsy

Carbamazepine is an antiepileptic used for focal seizures, for trigeminal neuralgia, and as a mood stabiliser.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Epilepsy: initially 100-200 mg once to twice daily

Route: oral

Frequency: in two or three divided doses

Max: up to 2000 mg/day (patients requiring doses exceeding 1200 mg should be switched to alternative oral formulations such as immediate release and prolonged release tablets)

A gradually increasing dosage scheme is advised, adjusted to the individual patient. Start low (100-200 mg once to twice daily) then increase slowly until best response obtained, often 800-1200 mg daily. Because the oral suspension gives higher peak levels than tablets, start with low doses of the liquid and increase slowly. Usually given in two or three divided doses. Treatment aims for total plasma-carbamazepine concentrations of about 4-12 micrograms/mL (17-50 micromoles/litre). Trigeminal neuralgia: initial 200-400 mg daily, raised slowly until pain-free (normally 200 mg 3-4 times daily), max 1200 mg/day. Prophylaxis of manic depressive psychosis (unresponsive to lithium): initial 400 mg daily in divided doses, increasing to a max of 1200 mg; usual range 400-600 mg daily. Elderly: dose selected with caution due to drug interactions.

Paediatric dose

Dose: 10 mg/kg

Route: oral

Frequency: daily in several divided doses

Max: From >=4 weeks up to 6 years: 35 mg/kg/day; 6 to 15 years: 1000 mg/day; 15 years: 1200 mg/day

Children (4 weeks of age or above) and adolescents: usual dosage 10-20 mg/kg bodyweight daily in several divided doses, using a gradually increasing dosage scheme adjusted to the individual patient. Approximate age bands quoted: 100-200 mg daily (from >=4 weeks up to 1 year), 200-400 mg daily (1-5 years), 400-600 mg daily (5-10 years), 600-1000 mg daily (10-15 years), 800-1200 mg daily (15 years, same as adult dose). Oral suspension contraindicated in children under 4 weeks of age. Verify paediatric dosing against a children's formulary.

Dose adjustments

Renal

No data are available on the pharmacokinetics of carbamazepine in patients with impaired hepatic or renal function.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION (SEE TABLE BELOW) Carbamazepine suspension in combination with liquid chlorpromazine or thioridazine results in precipitate formation, and, in the case of chlorpromazine, there has been a report of patient passing an orange rubbery precipitate in the stool following coadministration of the two drugs (see PRECAUTIONS, Drug Interactions). Because the extent to which this occurs with other liquid medications is not known, Carbamazepine suspension should not be administered simultaneously with other liquid medications or diluents. Monitoring of blood levels has increased the efficacy and safety of anticonvulsants (see PRECAUTIONS, Laboratory Tests). Dosage should be …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-02-18. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Known hypersensitivity to carbamazepine or structurally related drugs (e.g. tricyclic antidepressants) or any other component of the formulation
Atrioventricular block
History of bone marrow depression
History of hepatic porphyrias (e.g. acute intermittent porphyria, variegate porphyria, porphyria cutanea tarda)
Combination with monoamine oxidase inhibitors (MAOIs)
Oral suspension: children less than 4 weeks of age (excipient propylene glycol)

Side effects

Dizziness, headache, ataxia, drowsiness, fatigue, diplopia (CNS - very common/common, especially at start or if initial dose too high)
Nausea, vomiting (gastrointestinal disturbances)
Allergic skin reactions
Leucopenia (very common); thrombocytopenia, eosinophilia (common)
Oedema, fluid retention, weight increase, hyponatraemia (ADH-like effect); agranulocytosis, aplastic anaemia (very rare)

Interactions

Monoamine oxidase inhibitors (MAOIs) - contraindicated
CYP3A4 inhibitors (e.g. cimetidine, diltiazem, macrolides such as erythromycin/clarithromycin, fluoxetine, danazol, ciprofloxacin, aprepitant) can increase plasma carbamazepine levels
When co-prescribed with drugs that increase or decrease carbamazepine levels, close monitoring of levels and dosage adjustment may be required
Screen patients of Han Chinese and Thai origin for HLA-B*1502 where possible before initiation (risk of severe carbamazepine-associated Stevens-Johnson syndrome)

Clinical monograph

How it works

It stabilises neuronal membranes by blocking voltage-gated sodium channels.

Prescribing in practice

It is a strong enzyme inducer with many interactions, and it lowers the effectiveness of numerous drugs including hormonal contraceptives.
Serious rashes (Stevens-Johnson syndrome) occur, with higher risk in people carrying HLA-B*1502 (test in relevant ancestries); hyponatraemia and blood dyscrasias also occur.
It is teratogenic — specialist advice is needed around pregnancy; titrate slowly and avoid abrupt withdrawal.

Monitoring

Monitor for rash and check FBC, sodium and liver function; carbamazepine levels can guide dosing; review interacting drugs.

Counselling the patient

Report any rash, sore throat, fever, bruising or yellowing of the skin/eyes.
It can make other medicines (including the contraceptive pill) less effective — get advice.
Do not stop it suddenly.

Evidence & guidelines

An option for focal epilepsy and first-line for trigeminal neuralgia (NICE CG137/CG173), with important interaction, rash and pregnancy cautions.

Reference: NICE CG137; MHRA Drug Safety Update (HLA-B*1502); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways