Clinical evaluation of urapidil, a new antihypertensive drug: preliminary findings in Japan.

The pharmacokinetics, hypotensive effects, and safety of urapidil were investigated in 22 patients with essential hypertension at four coordinated centers in Japan. The drug was administered in sustained-release capsules given twice daily. The peak plasma concentration of the drug (measured in six patients) was observed four to six hours after administration, and 60% to 70% of the peak concentration was detectable at eight hours. These findings suggest that blood pressure might be controlled by twice-daily administration of urapidil. In 14 outpatients, who received 40 to 80 mg/day of urapidil, systolic and mean blood pressure decreased significantly (P less than 0.05) by week 4, and systolic, diastolic, and mean blood pressure decreased significantly (P less than 0.001) by week 6. In four inpatients, treated with 60 to 120 mg/day of the drug for two weeks, there were significant decreases (P less than 0.05) in systolic, diastolic, and mean blood pressure at day 6 and significant decreases (P less than 0.01) in diastolic and mean blood pressure at day 13. Although side effects were noted in five (23%) of the 22 patients, they were transient and slight in three; in two patients, the side effects disappeared after use of the medication was discontinued. Because the study was carried out in a small number of patients who received different dosages of urapidil over a short period of time, the optimal dosage was not established.