Pharmacology of valproic acid in children with severe epilepsy: clearance and hepatotoxicity.

Valproic acid concentrations correlate with dose in children when sampling times are consistent. Both interpatient variability and average clearance of valproic acid are inversely related to age. Young children usually need higher doses to achieve the same blood levels as other patients, but the levels that result from a dose are less predictable from one child to the next. Whereas valproic acid therapy had little effect on the serum glutamic oxaloacetic transaminase (SGOT), 12% of patients had abnormal SGOTs during an average of 14 months' therapy. The abnormal SGOTs from patients without serious hepatic dysfunction overlap many of the abnormal values in cases of fatal hepatic failure associated with valproic acid.