Effect of prazosin on renal function in congestive heart failure

Prazosin improves hemodynamics promptly in patients with congestive heart failure (CHF), but tolerance to repeated doses may develop rapidly. To determine if the kidneys play a role in this attenuation of effect, we studied renal responses in nine CHF patients treated with prazosin (5 mg three times a day for 3 days) preceded and followed by 3 days of placebo. Prazosin decreased mean arterial blood pressure from 87.0 +/- 2.2 (mean +/- SEM) to 84.0 +/- 2.0 mm Hg (p < 0.05) with no change in heart rate (73.1 +/- 3.3 bpm on placebo and 73.6 +/- 3.5 bpm on prazosin). The change in creatinine clearance from 81.6 +/- 8.7 to 96.3 +/- 10.4 ml/min with prazosin was not statistically significant, but the slight increase in urine volume from 2.33 +/- 0.22 to 2.51 +/- 0.23 1/24 hr was (p < 0.01). There were no significant changes in serum sodium, potassium, chloride, CO2, blood urea nitrogen, osmolality or glucose, urinary excretion of sodium or potassium, or sodium balance. The data were analyzed for changes within each period but there were no significant changes from day to day. Plasma renin activity rose from 3.93 +/- 0.69 to 4.96 +/- 0.84 ng/ml/hr during prazosin (p < 0.02). Significant alterations in renal function are not likely when patients with CHF are treated with prazosin, and any attenuation of effect of prazosin after repeated doses is not likely due to mechanisms involving alterations in renal function.