Anticonvulsant drugs

Abstract

For partial seizures, most commonly complex partial seizures (temporal lobe epilepsy) and for secondary tonic-clonic seizures in children and adolescents, carbamazepine is preferred to avoid the subtle dulling of mental function that may occur with the older drugs. In older patients phenytoin is usually satisfactory. When primary tonic-clonic seizures (grand mal) occur only in young people, valproate is preferred; phenytoin is used in older patients. If absence attacks or myoclonus also occur in addition to tonic-clonic seizures valproate is clearly the treatment of choice, but clonazepam is an important alternative. Phenobarbitone and primidone are second line drugs because of sedation and behaviour disorders. When absence attacks (petit mal) only occur, ethosuximide may be preferable to valproate only because of hepatotoxicity with valproate, but if there are other types of seizures valproate becomes preferable despite the hepatic risks. Myoclonus may be treated either with valproate or, if ineffective, with clonazepam. Other anticonvulsants are much less effective. For status epilepticus intravenous diazepam (0.15-0.25 mg/kg at a rate of 2.5 mg per minute) or clonazepam (adults 1 mg, children 0.5 mg over 30 seconds) are the treatments of choice. If control is not rapidly achieved it is better to change to another regimen than to continue to load with benzodiazepines. The choices are intravenous chlormethiazole or intravenous phenytoin, for paraldehyde has declined in use. Phenytoin, given as a loading intravenous infusion of 10-15 mg/kg at a rate of under 50 mg/minute (not intramuscularly), has the advantage that the transition to oral anticonvulsants is easier, whereas other anticonvulsants have to be introduced for maintenance treatment after intravenous chlormethiazole. Intravenous thiopentone administered in an intensive care unit, with facilities for ventilation and preferably for electroencephalographic monitoring also, is a last resort, and is usually effective.