Comparative renal effects of intravenous administration of fenoldopam mesylate and sodium nitroprusside in patients with severe hypertension.

We studied the renal effects of intravenous administration of fenoldopam mesylate, a dopamine-1 agonist, vs sodium nitroprusside following acute reduction of blood pressure (BP) in 11 patients with severe hypertension (supine BP, 168/124 to 252/135 mm Hg). Following randomization (open-label), timed urinary and plasma samples for clearance of urea and creatinine and excretion of sodium, potassium, and calcium were obtained as well as plasma renin activity for a two-hour collection prior to infusion, during a two-hour period of BP control (supine diastolic BP, 95 to 110 mm Hg), and following two hours off the drugs. Mean arterial pressure was lowered similarly with the two drugs (-22% on fenoldopam vs -20% on nitroprusside; P = NS), and neither plasma renin activity nor plasma aldosterone concentration were changed by either drug. However, patients receiving fenoldopam had significant increases in urinary flow and excretion of sodium, potassium, and calcium, whereas patients receiving nitroprusside had no changes in these parameters. Patients receiving fenoldopam had a net fluid balance of -334 mL from the end of baseline to the end of the treatment period, while the nitroprusside group had a positive balance of 382 mL. Thus, these findings show that acute BP reduction with fenoldopam is associated with both a diuresis and natriuresis in severely hypertensive patients while lowering BP with nitroprusside does not predictably alter renal function and causes a moderate expansion in volume.