Oral versus intravenous AHPrBP (APD) in the treatment of hypercalcemia of malignancy.

Twenty patients with malignant hypercalcemia were treated with aminohydroxypropylidene bisphosphonate (AHPrBP, previously APD) a potent inhibitor of osteoclast-mediated bone resorption. To assess the efficacy of oral vs intravenous therapy, the patients were divided into two groups: group A received AHPrBP intravenously (30 mg/day), and group B received the drug orally (1200 mg/day) for 6 days. In both groups all the patients responded to AHPrBP with a rapid decrease in plasma calcium concentration after a mean time lag of 1 day. Within 9 days plasma calcium concentration fell from 3.42 +/- 0.13 (mean +/- SEM) to 2.26 +/- 0.13 mmol/l in group A and from 3.28 +/- 0.12 to 2.24 +/- 0.09 mmol/l in group B. There was no significant difference in plasma Ca level between both groups on days 4, 6, and 9, and plasma Ca was within the normal range in all patients on day 9. On both treatment regimens urinary calcium excretion fell dramatically and similarly. Plasma phosphate concentration decreased significantly on AHPrBP in both groups of patients, reaching values slightly below the normal range from day 4 to day 9. TmP/GFR decreased progressively on AHPrBP. However, this decrement was significant at day 6 only. Plasma parathyroid hormone concentration rose significantly in both groups from day 4 to day 9. We conclude that at the doses used in the present study treatment of tumor-induced hypercalcemia with AHPrBP is equally effective whether given orally or intravenously.