Serum concentrations of phenytoin and phenobarbital which were administered as the tablet or the powder in epileptic patients were determined by the fluorescence polarization immunoassay method. The serum concentrations of phenytoin administered as the tablet (Hydantol®) were higher than those as the powder (Aleviatin ® fine granules). To investigate the differences in serum levels following administration of each preparation, compliance, dissolution characteristics of the preparations and losses of the powder after operating the dividing and packing machines were investigated. Since phenytoin dissolved from the Hydantol ® tablet more slowly than from the Aleviatin ® fine granules, the differences in dissolution rates of both preparations do not seem to be the cause of higher serum concentrations in patients taking the Hydantol ® tablet.
The amount of the powder after operating three types of dividing and packing machines was decreased about 2-8% of the original amount of the powder by adhesion to various dividing sites of the machine. Accordingly, the lower serum concentrations of phenytoin after the administration of the powder may be due to losses of the powder by the adhesion to dividing and packing machine and due to non-compliance.
Although there was no significant difference in the serum concentrations of phenobarbital between the tablet (Phenobal ®) and the powder (JP X phenobarbital powder), large variations in the serum concentrations were observed following administration of the powder. In view of the result of questionnaire and bitterness of the drug, a possibility of non-compliance of the powder was considered. Thus, it may be suggested that these factors should be concerned invariations of the serum concentrations.
