Abstract

Bisphosphonates (formerly diphosphonates), analogues of endogenous pyrophosphates, are potent inhibitors of osteoclastic bone resorption. While the exact mechanism of action remains poorly understood, etidronate, the only bisphosphonate currently available in the United States for the treatment of hypercalcemia, decreases the elevated serum calcium levels and alleviates the symptoms associated with hypercalcemia of malignancy. Both open and controlled clinical studies have demonstrated that this agent, administered at a dose of 7.5 mg/kg/d in 2-hour intravenous infusions over 3 to 7 days, promotes normocalcemia. In a randomized study, etidronate was shown to be superior to maximally approved doses of calcitonin. Moreover, when administered to patients without overt renal failure (serum creatinine less than 2.5 mg/dL), the drug is remarkably free of significant acute toxicity and side effects. Therefore, an important therapeutic aspect of this agent is that it permits concurrent antibiotic and chemotherapy administration. Judicious use of appropriate and specific pharmacologic intervention strategies in the patient with cancer-related hypercalcemia is expected to enhance quality of life, improve systemic cancer therapy tolerance, and reduce the morbidity of this serious neoplastic complication.