The effect of bendroflumethiazide on the intestinal absorption of calcium in normocalcaemic renal stone formers and in hyperparathyroidism.

Abstract. While the hypocalciuric action of thiazides is well established, their action on the intestinal absorption of calcium has remained a matter of dispute. In the present investigation this action has been studied in man by the measurement of forearm radioactivity in an Armac large volume liquid scintillation counter following separate oral and i.v. administration of 47Ca. Determined in this way duplicate measurements of calcium absorption in the same individual yield a standard deviation of 3.2%. Oral administration of bendroflumethiazide, 10 mg/day, led to a significant increase in fractional calcium absorption in a group comprising patients with hypercalcaemic hyperparathyroidism (n = 7), normocalcaemic renal stone disease (n = 8) and postsurgical hypoparathyroidism (n = 1). The mode of action of thiazides on the intestinal calcium absorption is discussed. Probably thiazides promote in a specific way the transport of calcium through the intestinal as well as through the tubular epithelial cells.