Preliminary evidence for the mechanism underlying the development of tolerance to prazosin in congestive heart failure: the alpha-agonistic properties of dobutamine unmasked by prazosin treatment.

The hemodynamic effects of acute and chronic treatment with different vasodilators were assessed in patients with chronic heart failure of New York Heart Association (NYHA) class III-IV. Each of 24 patients was randomly allocated; 6 to each of four groups: isosorbide dinitrate, dihydralazine, captopril, or prazosin. In addition, we evaluated the hemodynamic response to dobutamine by using increasing infusion rates of 2.