EFFECT OF HYDROCHLOROTHIAZIDE ON SERUM + URINARY CALCIUM + URINARY CITRATE

Abstract

Benzothiadiazines, potent oral diuretics, also inhibit carbonic anhydrase, although to a lesser degree than acetazolamide (Diamox). The latter has little effect on urinary Ca but causes hypocitriuria which predisposes to nephro-lithiasis. The effect of benzothiadiazines on urinary calcium/citrate balance is less well known. In this study, the fall of urinary calcium and citrate was roughly 50% and 30%, respectively, in normal and hypertensive subjects during the prolonged administration of hydrochlorothiazide, a member of the benzothiadiazine family. Hence, in contradistinction to acetazolamide, this drug produces hypocalciuria but depresses the urinary citrate less. Consequently, the benzothiadiazines would not be expected to predispose to nephrolithiasis. In addition, hydrochlorothiazide was found to produce a 10-20% fall in creatinine clearance and an initial rise of roughly 0.7 mg./100 ml. in serum Ca concentration. There are indications that the benzothiadiazines affect the overall metabolism of Ca and citrate.