A new oral renal vasodilator, fenoldopam

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Abstract
Fenoldopam, a dopamine agonist, was evaluated in renal clearance studies during water diuresis after oral doses of 25, 50 and 100 mg. After the 100-mg dose, there was an increase in urine flow rate, paraaminohippurate clearance, free water clearance and an increase in the fractional excretion of Na, Ca and uric acid. These effects were evident within the 1st h, peaked during the 2nd h and lasted about 3 h. Doses of 50 and 25 mg induced smaller increases. There was no significant change in inulin clearance at any dose. To elucidate the mechanism of action, the studies were repeated after treatment with a dopamine-receptor antagonist (metoclopramide). Metoclopramide greatly diminished the renal effects of fenoldopam. Fenoldopam is evidently an active renal vasodilator in man and increases urine volume, free water clearance and fractional excretion of Na by stimulation of renal dopamine receptors.