The pharmacokinetics and effects of prazosin have been studied after intravenous and oral dosing (1 mg) to 6 normal male volunteers. The mean terminal () half-life was 2.9 h after intravenous and oral routes. Oral bioavailability was 56.9%. The effects of prazosin on blood pressure were more pronounced after intravenous than oral administration, and the hypotensive effect greater on erect blood pressure. There was a significant correlation (P<0.02) between="" the="" fall="" in="" blood="" pressure="" and="" the="" plasma="" drug="" concentration="" after="" intravenous="">