Indications: all forms of epilepsy except absence seizures; status epilepticus; prophylaxis of seizures in neurosurgery.

Cautions: avoid abrupt withdrawal; avoid in porphyria; hepatic impairment; pregnancy; breast-feeding: hepatic failure; sudden withdrawal and change to other drugs should be made cautiously.

Side Effects: nausea, vomiting, constipation, insomnia, transient nervousness, tremor, paraesthesia, dizziness, headache, anorexia; gingival hypertrophy and tenderness; rash (discontinue; if mild re-introduce cautiously but discontinue immediately if recurrence), acne, hirsutism, coarse facies; rarely hepatoxicity, peripheral neuropathy, dyskinesia, lymphadenopathy, osteomalacia, blood disorders (including megaloblastic anaemia (may be treated with folic acid), leucopenia, thrombocytopenia, and aplastic anaemia), polyarteritis nodosa, lupus erythematosus, Stevens-Johnson syndrome, and toxic epidermal necrolysis; with excessive dosage nystagmus, diplopia, slurred speech, ataxia, confusion, and hyperglycaemia.

Dose: by mouth, daily as a single dose or 2 divided doses, with water, 150-300 mg increased gradually to 600 mg according to the patient's needs (with plasma- phenytoin concentration monitoring).

Usual dose, 200-500 mg daily.

Child, 5-8 mg/kg daily in 1 or 2 doses; max. 300 mg daily.

By slow IV injection or infusion, status epilepticus, 13-15 mg/kg at a rate not exceeding 50 mg per minute, as a loading dose; Maintenance doses of about 100 mg should be given thereafter at intervals of every 6 hours.

Note: Plasma concentration for optimum response 10–20 mg/litre (40–80 micromol/litre)

Take preferably with or after food.