Site of renal action of xipamide.

Xipamide, hydrochlorothiazide, and furosemide were given to normal volunteers on a double-blind basis. During maximal water diuresis, there was a reduction in free water clearance and an increase in osmolar clearance after administration of xipamide and hydrochlorothiazide, but not in the case of furosemide. During maximal hydropenia, both xipamide and hydrochlorothiazide increased free water reabosorption in a linear relationship to osmolar clearance, while furosemide increased osmolar clearance with little change in free water reabsorption. It was concluded, therefore, that, as with hydrochlorothiazide, the site of action of xipamide was on the distal convoluted tubule, and that of furosemide on the loop of Henle.