Plasma renin activity and plasma concentrations of norepinephrine and cyclic nucleotides in heart failure after prazosin.

A single oral dose of 1.0 to 2.0 mg prazosin was given to 14 patients with congestive heart failure to assess its effect. Prazosin increased cardiac index (+27.5%) and decreased pulmonary arterial diastolic pressure (-29.1%), systemic vascular resistance (-27.7%), mean blood pressure (-11.8%), and double products (-12.9%). Plasma renin activity (¿.8%) and plasma concentrations of norepinephrine (+67.5%) and cyclic adenosine monophosphate (AMP) (+10.6%) rose. There was a negative correlation between plasma cyclic AMP concentration and the increase of plasma cyclic AMP concentration after prazosin (Y = -0.53X + 18.7). There were no changes in heart rate and plasma cyclic guanosine monophosphate concentration. The effects were maximum at 3 hr and lasted 5 hr. The results indicate that oral prazosin has a beneficial hemodynamic effect in patients with congestive heart failure, and that the pathologic effects of prazosin, "alpha-blocker." induces a rise in plasma renin activity as well as in plasma concentrations of norepinephrine and cyclic AMP.