Prorenoate Potassium is a water-soluble synthetic aldosterone antagonist patented by Merck and Co., Inc. as an antihypertensive agent. In preclinical studies a significant natriuretic response was obtained at dosages of 1 mg/kg and approximately 1.8 mg/kg in the dog and rat, respectively. Prorenoate is relatively inactive at the renal level in adrenalectomized rats without mineralocorticoid replacement. Prorenoate possesses no more than 2% of the natriuretic activity of hydrochlorothiazide in the intact animal. Clearance studies in dogs indicate a direct renal tubular site of interaction between prorenoate and aldosterone independent of changes in renal hemodynamics. The natriuretic response occurred within 100 minutes after a single oral dose and was sustained for at least 7 hours. In clinical trials Prorenoate reversing the renal effects of the synthetic mineralocorticoid fludrocortisone in healthy individuals. Prorenoate was significantly more potent in retaining K+ than in increasing Na+ excretion.