Indications & Dose: ESSENTIAL TREMOR PO Adult Initially 62.5mg/day, increase gradually over 2–3 wk according to response, max 750mg/day | SEIZURE DISORDERS PO Adult Initially 125mg HS, increase by 125mg q3days to 500mg/day in 2 divided doses, then increase according to response by 250mg q3days, MD 0.75–1.5g/day in 2 divided doses Child 2-18 yr: Initially 125mg/day HS, increase by 125mg q3days according to response, MD 125–250mg BID (<2yr), 250–375mg BID (2–5 yr), 375–500mg BID (5–9 yr), max 750mg BID (9-18yr)

Precautions: Avoid abrupt withdrawal, hepatic/renal impairment, elderly, respiratory depression, history of drug/alcohol abuse

ADR: Serious: SJS, TEN, hepatitis, thrombocytopenia, respiratory depression, hypotension, osteomalacia, Others: nausea, vomiting, dizziness, headache, behavioural disturbances, nystagmus, drowsiness, irritability, lethargy, ataxia, arthralgia, hallucinations, impaired memory, hyperactivity

DDI: Serious Benzodiazepines causes increased sedation during initial use, Acetazolamide causes severe osteomalacia and rickets, Etoposide clearance is increased, Folic acid decreases drug efficacy, Methyl Prednisolone/Dexamethasone/Prednisolone/Prednisone/Vincristine efficacy is reduced, Isoniazid/Felbamate/Phenytoin increases drug level, Paroxetine/Fluoxetine/Venlafaxine increases drug levels and lead to neuroleptic malignant syndrome and extra pyramidal symptoms, Alcohol increases sedation, Cyclopropane/Bupropion/Quinidine level is decreased, Mirtazapine/Doxycycline level is reduced, Imatinib/Fentanyl levels are reduced, Coumarins levels are significantly reduced, Mebendazole/Albendazole plasma levels are reduced, Combined hormonal contraceptives steroid levels are reduced

Diet: With/without food

Monitor: Serum drug & phenobarbital levels, neurological status, CBC