薬理と治療

Abstract

Background Phenytoin（PHT）, an anti－epileptic drug, displays non－linear pharmacokinetics at therapeutic blood concentration, and premeditated PHT dosage based on the weight of each patient should be administered to obtain therapeutic blood concentrations. Objective The purpose of this study was to analyze a correlation between the consciousness level of a neurosurgical patients and an adequate dosage of PHT. Methods A PHT dosage of 5 or 7 mg／kg／day was administered by dividing into twice a day （7：00 and 19：00）for one week in 20 neurosurgical patients. Each PHT dose was dissolved in 50 mL of saline and administered over 30 minutes. The PHT blood concentration was evaluated on days 4 and 8 day after initiating PHT therapy at 7：00 just before PHT administration. Results The PHT blood concentration at day 7 was 2.5±0.9 μg／mL in four patients given 5 mg／kg／day dosage, and was 11.6±2.2 μg／mL in 16 patients given 7 mg／kg／day dosage. Among the latter 16 higher dose patients, the PHT blood concentration on day 7 was 15.8± 2.5 μg／mL in patients with a score of 3 or lower on Japan coma scale（JCS）, whereas it was 8.6±1.6 μg／mL in patients with a score of 10 or higher. Conclusions A PHT dosage of 7 mg／kg／day might be sufficient to acquire a therapeutic PHT blood concentration within one week；however, a higher dosage may be required when the patient has a JCS score of 10 or higher.