Dose-response in the treatment of hypercalcemia of malignancy by a single infusion of the bisphosphonate AHPrBP.

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Abstract
Fifty-two patients with malignant hypercalcemia were treated with a single dose of 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP, previously APD), a potent inhibitor of osteoclast-mediated bone resorption. In order to establish a dose-response in humans, patients were divided into four groups receiving 30 mg, 45 mg, 60 mg, or 90 mg, respectively, as a 24-hour infusion. Initial plasma calcium was similar in all groups, except in the group receiving 90 mg, of which some patients had higher initial values. All patients responded to AHPrBP with a rapid decrease of plasma calcium concentration from 3.47 .+-. 0.10 mmol/L at day 0 to 2.43 .+-. 0.06 at day 6 (P < .001). Plasma calcium became normal within four to six days in 43 patients. Eight of the nine patients whose calcium did not become normal were in the low-dose (30 and 45 mg of AHPrBP) groups. Slight and asymptomatic hypocalcemia occurred in only two of the 26 patients in the low-dose groups, but in six of the 26 patients in the high-dose groups. A follow-up study in 40 patients that hypercalcemia recurred within 1 month in five of ten patients in the group receiving 30 mg, in three of ten patients in the group receiving 45 mg, and in one of 20 patients in the groups receiving 60 and 90 mg, whereas mortality was almost identical in all four groups. In all groups, plasma phosphate, plasma creatinine, urinary calcium, and hydroxyproline excretion decreased significantly. In conclusion, when administered as a single-day infusion in the treatment of tumor hypercalcemia, AHPrBP leads to a dose-dependent decrease in plasma calcium. To prevent transient hypocalcemia and early relapse, the optimal dose should be adapted to the degree of severity of hypercalcemia.