Anticonvulsant doses and side effects
| ANTICONVULSANT | STARTING DOSE | USUAL EFFECTIVE DOSE | SIDE EFFECTS |
|---|---|---|---|
| Phenytoin | NA | 200–500 mg/d in single or divided doses | Drug-drug interactions including dexamethasone, CNS (ataxia), liver, GI, dermatologic, hirsutism, anemia, osteoporosis |
| Carbamazepine | 200 mg/d; increase by 200 mg/wk | 300–1600 mg/d in 3–4 divided doses or 2 divided doses if long-acting | Drug-drug interactions, SIADH, CNS (sedation, vertigo, ataxia, diplopia), myelotoxicity |
| Valproic acid | 15 mg/kg daily; 250–500 mg/d, increased weekly by 250 mg/wk | 1000–3000 mg/d, up to 60 mg/kg daily (check serum levels) in 3 divided doses or 2 divided doses if long-acting; decrease dose if hepatic failure occurs | Drug-drug interactions, CNS (ataxia, tremors, sedation), weight gain, hair loss, GI, thrombocytopenia, liver toxicity |
| Oxcarbazepine | 300–600 mg/d | 900–2400 mg/d; decrease dose if renal failure occurs | Hyponatremia, dizziness, somnolence, nausea, ataxia, diplopia |
| Phenobarbital | NA | 60–250 mg/d, maximum 600 mg/d (1–5 mg/kg in adults) in single or divided doses; decrease dose if renal or hepatic failure occur | Drug-drug interactions, CNS depressor, respiratory depression, somnolence, rash |
| Gabapentin | NA | 300–3600 mg/d as monotherapy; up to 1800 mg/d as adjuvant therapy, in 3–4 divided doses; decrease dose if renal failure occurs | Interaction with antacids; decrease in memory and concentration; somnolence, ataxia, dizziness, edema, weight gain |
| Lamotrigine | 50 mg/d for 2 wk, then increase by 25–50 mg/wk | 100–500 mg/d in 2 divided doses; decrease dose if renal or hepatic failure occur | Rash, especially if dose escalation is rapid |
| Topiramate | 25 mg/d; increase by 25–50 mg/wk | 75–400 mg/d in 2 divided doses; decrease dose if renal failure occurs | Drug-drug interactions, somnolence, confusion, weight loss, metabolic acidosis, angle-closure glaucoma |
| Levetiracetam | 750–1000 mg/d | 1000–3000 mg/d in 2 divided doses; decrease dose if renal failure occurs | Anxiety, aggressivity, somnolence, asthenia, dizziness |
| Clobazam | 10 mg/d | 10–30 mg/d, maximum 60–80 mg/d in 2 divided doses | Same as for benzodiazepines; rash |
| Clonazepam | NA | 1–6 mg/d in 2–3 divided doses | Same as for benzodiazepines; paradoxical excitation |
CNS—central nervous system, GI—gastrointestinal, NA—not applicable, SIADH—syndrome of inappropriate antidiuretic hormone secretion.
Data from Beaulieu and Nadeau,3 and Caraceni et al.5