Comparison of different intravenous bisphosphonate regimens for Paget's disease of bone

Introduction: Intravenous bisphosphonates represent a common therapy for Paget's disease of bone (PDB). However, there have been few head to head randomized trials comparing intravenous bisphosphonates. Materials and Methods: We performed a 1.5-mo, randomized study comparing different intravenous bisphosphonates in 90 subjects with active PDB. At baseline, patients were randomly assigned to receive pamidronate (30 mg, IV, for 2 consecutive days every 3 mo; n = 60) or zoledronate (4 mg, IV; n = 30). After 6 mo, nonresponders to pamidronate were crossed over to zoledronate or neridronate (100 mg, IV, for 2 consecutive days). The primary efficacy endpoint was therapeutic response at 6 mo, defined as normalization of alkaline phosphatase (ALP) or a reduction of at least 75% in total ALP excess. Results: At 6 mo, 97% of patients receiving zoledronate had a therapeutic response compared with 45% of patients receiving pamidronate. Normalization of ALP was achieved in 93% of patients in the zoledronate group and in 35% of patients in the pamidronate group. ALP normalization was maintained in 79% and 65% of zoledronate-treated patients after 12 and 15 mo, respectively; loss of therapeutic response was observed in 2 of 30 (6%) at 12 and 15 mo. At 6 mo, 27 patients showing therapeutic response to pamidronate continued the treatment, whereas nonresponders were crossed-over to neridronate (n = 15) or zoledronate (n = 18). Among these subjects, 14 of 15 (93%) in the neridronate group and 17 of 18 (94%) in the zoledronate group achieved a therapeutic response. Similar normalization rates were observed between neridronate- (80%) and zoledronate- (83%) treated subjects. Normalization and therapeutic response were maintained at 9 mo from treatment (corresponding to 15 mo from the baseline visit) in either neridronate or zoledronate groups. Conclusions: Single neridronate and zoledronate infusion showed a similar efficacy in achieving biochemical remission in up to 90% of patients nonresponders to pamidronate. Therapeutic response to zoledronate seems to be maintained in most patients at 15 mo.