Investigation of the Therapeutic Drug Monitoring of Valproic Acid(VAP) and the Effects of Other Epileptics on the Concentration of VAP at Miyazaki Medical College Hospital.

The present study was undertaken to investigate the annual number of antiepileptic drug monitoring samples (mainly valproic acid, VAP), the rate of effective therapeutic concentration area and the effect of other epileptics on the serum concentration of VAP at Miyazaki Medical College Hospital between 1984 and 1996. The most frequently assayed drugs in antiepileptics shifted from VAP to phenytoin in 1990. The pediatric department most frequently requested the measurement of VPA in 1996. Sixty-five per cent of the VAP serum levels were within the effective therapeutic concentration area (50-100μg/ml), but the some rate for phenytoin was less than 40%. The serum concentration of VAP was reduced with the coadministration of other epileptic drugs and the degree of the reduction was different for phenytoin, phenobarbital and carbamazepine. The pediatric patients tended to show higher serum YAP concentrations than adult patients.These results suggested the serum level monitoring of VAP to be useful for drug therapy in epileptic patients.