Etidronate disodium in postmenopausal osteoporosis.

Calcium-balance, calcium-kinetic, and physiologic observations were made in 10 osteoporotic patients treated for 6 to 12 mo with disodium etidronate (EHDP) in oral doses of 20 mg/kg/day. Absorption of EHDP averaged 10%, and effective retained dose was approximately 1.6 mg/kg/day. Patient acceptance was excellent, and there were no detectable clinical or biochemical untoward effects of treatment. Serum phosphorus was elevated on average of 1.1 mg/100 ml, and serum calcium, 0.4 mg/100 ml. EHDP reduced bone resorption by about 50% and depressed bone mineralization by almost as much. Both the total miscible calcium pool and its component compartments were smaller on EHDP, presumably because of a combination of interference with bone mineral reactivity and the decrease in mineralization rate. Urine calcium was increased by a small, but highly significant, amount, and gastrointestinal calcium absorption was also significantly increased. Calcium balance shifted slightly but significantly in the positive direction. The magnitude of these changes correlated with the urinary level of EHDP.