Effects of Dichloromethylene Diphosphonate on Serum and Urinary Calcium in Primary Hyperparathyroidism

Abstract

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 < 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 < 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 < 0.01) and by a 40% reduction in the average urinary calcium excretion from 185 ± 29 to 113± 23 mg/g creatinine (p < 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.