Indications: partial and secondary generalised tonic- clonic seizures, some primary generalised seizures; trigeminal neuralgia; prophylaxis of bipolar disorder unresponsive to lithium.

Cautions: hepatic impairment or renal impairment; cardiac disease, skin reactions, history of haematological reactions to other drugs; may exacerbate absence and myoclonic seizures; susceptibility to angle-closure glaucoma; pregnancy, breast-feeding; avoid abrupt withdrawal.

Contra-indications: AV conduction abnormalities (unless paced); history of bone marrow depression, porphyria.

Side Effects: nausea and vomiting, dizziness, drowsiness, headache, ataxia, confusion and agitation (elderly), visual disturbances (especially diplopia); constipation or diarrhoea, anorexia; mild transient generalised erythematous rash may occur in a large number of patients (withdraw if worsens or is accompanied by other symptoms); leucopenia and other blood disorders (including thrombocytopenia, agranulocytosis and aplastic anaemia); other side effects include cholestatic jaundice, hepatitis and acute renal failure, Stevens-Johnson syndrome, toxic epidermal necrolysis, alopecia, thromboembolism, arthralgia, fever, proteinuria, lymph node enlargement, cardiac conduction disturbances (sometimes arrhythmias), dyskinesias, paraesthesia, depression, impotence (and impaired fertility), gynaecomastia, galactorrhoea, aggression, activation of psychosis; very rarely angle-closure glaucoma; photosensitivity, pulmonary hypersensitivity (with dyspnea and pneumonitis), hyponatraemia, oedema, and disturbances of bone metabolism (with osteomalacia).

Note: Different preparations may vary in bioavailability; to avoid reduced effect or excessive side effects, it may be prudent to avoid changing the formulation.

Dose: By mouth, epilepsy, initially, 100–200 mg 1–2 times daily, increased slowly to usual dose of 0.4–1.2 g daily in divided doses; in some cases 1.6–2 g daily may be needed; ELDERLY reduce initial dose;

CHILD daily in divided doses, up to 1 year 100–200 mg,

1–5 years 200–400 mg, 5–10 years 400–600 mg, 10–15 years 0.4–1 g.

Trigeminal neuralgia, initially 100 mg 1–2 times daily (but some patients may require higher initial dose), increased gradually according to response; usual dose 200 mg 3–4 times daily, up to 1.6 g daily in some patients.

Prophylaxis of bipolar disorder unresponsive to lithium, initially 400 mg daily in divided doses increased until symptoms controlled; usual range 400–600 mg daily; max. 1.6 g daily.

Note: Plasma concentration for optimum response 4–12 mg/litre (20–50 micromol/litre).