THE EFFECTS OF MEFRUSIDE IN THE WATER DIURETIC AND HYDROPENIC DOG: A COMPARISON WITH CHLOROTHIAZIDE

¹ Cardiovascular Research Laboratories, Department of Internal Medicine, University of Iowa, Iowa City, Iowa

Mefruside, a new diuretic compound of the 4-chloro-3-sulfonamide-bensenesulfonamide series was studied after large i.v. doses in water diuretic and hydropenic dogs. Its diuretic effects were compared to chlorothiazide. Mefruside produced a natniuresis and chloruresis under both conditions of study. Chlorothiazide produced a greater excretion of sodium and chloride which was accompanied by an increase in urine volume. Potassium excretion increased after chlorothiazide in both the hydropenic and water diuretic studies, whereas significant increases were noted after mefruside only during water diuresis, probably related to the weaker natriuretic effect of mefruside. Inulin dearance fell during the water diuretic experiments after both agents. Both drugs produced an increase in urinary pH and bicarbonate excretion with decreases in urinary ammonium excretion and urinary titratable acidity. Mefruside did not alter solute free water reabsorption but did decrease free water clearance relative to urine flow indicating blockade of sodium reabsorption in the functional cortical diluting segment of the ascending limb of the loop of Henle and distal nephron. These findings suggest that mefruside has a mechanism of action similar to the thiaside diuretics without any unique features. Mefruside is less effective acutely than is chlorothiazide.