Single-dose pharmacokinetics of labetalol in healthy young men

Single doses of labetalol (200 mg i.v. over 5 min, 200 and 400 mg orally) were given to five healthy men on three different occasions. Plasma levels were followed for up to 25 h and blood pressure for 5 h. The elimination half-life was 1.6 to 8.5 h for the first 8 h. The oral bioavailability ranged from 4 to 23%. All doses induced a significant fall in systolic blood pressure at 2 h, the peak effect occurring at 30--120 (mean 63-72) min. After intravenous administration the peak supine blood-pressure fall was significant for both systolic and diastolic blood pressure and occurred 16 min after administration.