Inhibition of crystal resorption occurs at lower doses than are required to inhibit crystal growth. Both effects increase as the dose increases. Didronel is not metabolized. Animal studies have yielded bone clearance estimates up to 165 days. In humans, the residence time on bone may vary due to such factors as specific metabolic condition and bone type.
Unabsorbed drug is excreted intact in the feces.
Preclinical studies indicate etidronate disodium does not cross the blood-brain barrier. Didronel therapy does not adversely affect serum levels of parathyroid hormone or calcium. Bone fractures are common in patients with Paget s disease. This has been demonstrated histoloically, scintigraphically, biochemically, and through calcium kinetic and balance studies. Reduced bone turnover is often accompanied by symptomatic improvement, including reduced bone pain.