Effects of dichloromethylene diphosphonate on serum and urinary calcium in primary hyperparathyroidism

Dichloromethylene diphosphonate (Cl2MDP), an inhibitor of osteoclast function, was evaluated for its ability to lower the serum and urinary calcium in 14 patients with primary hyperparathyroidism. The study was double-blind, placebo-controlled, and cross-over in design. All patients received 12 weeks of Cl2MDP (1600 mg daily) and 12 weeks of placebo in a randomized sequence. The average serum calcium was lowered by Cl2MDP from 11.5 +/- 0.1 mg/dL to 10.8 +/- 0.2 mg/dL (p less than 0.001). In the 3-month follow-up after drug administration, the average serum calcium (11.0 +/- 0.2 mg/dL) remained significantly below pretreatment levels (p less than 0.01). The reduction in serum calcium was accompanied by a significant decline in the urinary hydroxyproline excretion from 37 +/- 3 to 28 +/- 2 mg/g creatinine (p less than 0.01) and by a 40% reduction in the average urinary calcium excretion from 185 +/- 29 to 113 +/- 23 mg/g creatinine (p less than 0.01). Administration of Cl2MDP was not associated with any significant changes in parathyroid hormone levels or in urinary cyclic adenosine monophosphate excretion. No side effects were observed. We conclude that Cl2MDP lowers the serum and urinary calcium in patients with primary hyperparathyroidism.