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

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Abstract
A single oral dose of 1.0-2.0 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 (+25.8%) and plasma concentrations of norepinephrine [NE] (+67.5%) and cAMP (+10.6%) rose. There was a negative correlation between plasma cAMP concentration and the increase of plasma cAMP concentration after prazosin (Y = -0.53X + 18.7). There were no changes in heart rate and plasma cGMP concentration. The effects were maximum at 3 h and lasted 5 h. Oral prazosin has a beneficial hemodynamic effect in patients with congestive heart failure, and the pathologic effects of prazosin, .alpha.-blocker, induces a rise in plasma renin activity and in plasma concentrations of NE and cAMP.