EFFECTS OF CHLOROTHIAZIDE AND AMIPRAMIZIDE (MK 870) ON RENAL EXCRETION OF CALCIUM PHOSPHATE AND MAGNESIUM

Following the administration of a high priming and sustaining infusion of Chlorothiazide to dogs undergoing a diuresis, there was an increase in phosphate and ultrafilterable calcium clearance in spite of a fall in filtered load, while ultrafilterable magnesium did not change. When a dose four times lower was given to hydropenic dogs, the filtered load of magnesium and ultrafilterable magnesium clearance remained constant and clearance of phosphate and ultrafilterable calcium increased. Although Amipramizide increased the clearance of ultrafilterable calcium and magnesium, the change was not significant and phosphate clearance was not affected. A good correlation between the clearance of ultrafilterable calcium and that of sodium was found in all experiments, thus confirming previous reports suggesting that both ions are related in their renal tubular transport. The apparent discrepancy of these findings with other studies in which oral and intravenous Chlorothiazide decreased urinary calcium can be explained by postulating that the effects are related to the dosage used, the previous state of hydration, the replenishment of the urinary losses, and changes in filtered load. © 1968.