Treatment of primary hypercalciuria: Bisphosphonates
Bisphosphonates are widely used to prevent osteoporosis and, among these, alendronate and risedronate, exhibit a favourable efficacy/safety profile over long-term use. Theoretically, if increased bone resorption partly explained id- iopathic hypercalciuria, it follows that drugs capable of reducing the rate of bone turnover should also have some effect on calcium excretion. Alendronate, 20 mg daily, had been shown to prevent hypercalciuria and the calcium-stone forming propensity induced by prolonged bed-rest. Independently of immobilization, genetic hypercalciuric rats reduced both calcium excretion and urine saturation with calcium salts upon al- endronate administration. The effects of bisphosphonates on calcium excretion was studied in the phosphate depletion induced hypercalciuria, which is referred to as being caused by increased efflux of calcium from bone. Phosphate depleted rats developed hypophosphatemia, hypercalcemia and hypercalci- uria, but failed to respond to pamidronate, despite an improved bone histology. cheap generic drugs online
Recently we have reported similar results in patients with fasting hypercalciuria who had been given alendronate 10 mg/daily and re-studied after a three-month course. There was a significant decrease in both fasting and 24-hour calcium excretion and, consequently, a 43% reduction in urine saturation with calcium oxalate. These changes were obtained in the face of normal levels of plasma calcium and only minor and transient increases in serum PTH, and maintained over a two-year follow-up (Figure 3). From these results bisphosphonates appear as promising new tools in the management of hypercalciuria, namely in the fasting hypercalciuria or in patients with biochemical (and clinical) evidence of increased bone resorption.
Figure 3- Long-term effects ofAlendronate, 10 mg daily, on bone resorption (lower panel) and calcium excretion (upper panel) in hy- percalciuric patients. (* p<0.05; ** p<0.01 vs basal values).