健常人におけるLabetalolの薬物動態と薬理作用

抄録

Labetalol, a newly developed α, β-blocking agent, was orally administered to 5male healthy volunteers and its pharmacokinetics and pharmacodynamics wereinvestigated.
Serum and urine concentration of labetalol was determined by fluorometry. The time course of the serum concentration was able to be fitted to the two compartment open model. The time to the maximum serum concentration was 1-1.5 hours, and the maximum serum concentration was 21.8 ng/ml after 50 mg dose, 59.7ng/ml after 100 mg dose, and 163.3 ng/ml after 200 mg dose. The elimination half-life was 8.62-17.65 hours. The fraction of drug excreted in unchanged form into 0-24 hours' urine was about 2%.
Both systolic and diastolic blood pressures were significantly decreased by single oral dose of 50 mg, 100 mg and 200 mg in the supine, sitting and standing positions. The reduction of the blood pressure was bigger in standing position than in the supine and sitting positions. Exercise-induced elevation of systolic blood pressure and tachycardia were attenuated by the administration of labetalol. The percent reduction of exercise-induced tachycardia was significantly correlated with the logarithm of the serum concentration of labetalol.
In some subjects, scalp tingling, tiredness of the lower legs during exercise, drowsiness, nausea and postural dizziness were complained above the dose of 100mg in this study.