Hemodynamic changes at rest and during exercise in long-term prazosin therapy for essential hypertension.

Fourteen men 30 to 50 years of age (mean, 42) with untreated essential hypertension, WHO stage I or II, and no other demonstrable disease were studied as outpatients. Oxygen consumption, heart rate, cardiac output, and intraarterial brachial pressure were recorded at rest in the supine and sitting positions and during exercise in the form of bicycling. The subjects were then treated with prazosin in a dosage of 3 to 7.5 mg/day. Eleven subjects responded well, and in 10 of these the hemodynamic study was repeated after one year. At the time of restudy, the systolic, diastolic, and mean arterial pressures were reduced about 11% at rest and during exercise. Pressure reduction was associated with a marked decrease in the previously increased total peripheral resistance of about 17% during rest and 22% during exercise. In all but two subjects, total peripheral resistance was reduced 10% or more at rest and during exercise. During exercise, the total peripheral resistance was reduced more than 10% in all subjects. Heart rate and cardiac output were not changed significantly but tended to be higher after one year of therapy. A comparison of the results with those obtained in patients treated with other antihypertensive agents shows that the reduction in total peripheral resistance was greatest in the group receiving prazosin.