Prazosin enhances the antihypertensive effects of beta-blockers during isometric and dynamic exercise

Eighteen hypertensive (WHO I-II) outpatients volunteering for an open comparative cross-over trial were treated with the non-selective beta-blocker sotalol (80 mg b.i.d.) the beta-selective atenolol (50 mg b.i.d.) alone and each in combination with prazosin (3-5 mg b.i.d.) for 4 to 8 weeks each in balanced order. The blood pressure (BP) and heart rate (HR) were measured sitting and standing as well as during relatively heavy dynamic (ergometer) and isometric (sustained handgrip) exercises. The four-week treatment with sotalol lowered the HR without much influence on the BP. Atenolol similarly lowered the HR but was somewhat more active on the BP. Both beta-blockers failed to modify the pressor responses to exercise significantly. The addition of prazosin to beta-blockers improved their efficacy. Lowered BP values were recorded during dynamic and even isometric work, partly due to lowered baseline BP levels. The side effects were generally mild, and no excessive hypotension was encountered. The results suggest that the antihypertensive combination of the vasodilator, prazosin, with moderate doses of beta-blockers may be valuable in helping patients to maintain lower blood pressures during daily physical stress.