Comparison of intravenous and intramuscular neridronate regimens for the treatment of Paget disease of bone

Aminobisphosphonates actually represent the most common treatment for Paget disease of bone (PDB). In a previous study we demonstrated that either zoledronic acid (4 mg) or neridronate (200 mg) given as a single intravenous infusion showed a similar short-term efficacy in achieving biochemical remission in up to 90% of patient nonresponders to pamidronate. In this study we compared the long-term (36 months) effects of a same neridronate dose (200 mg) given as an intravenous (100-mg infusion for 2 consecutive days) or intramuscular (25-mg injection weekly for 2 months) regimen in 56 patients with active PDB. All patients were advised to receive calcium plus vitamin D supplementation throughout the study period. At 6 months, 92.6% and 96.5% of patients receiving intravenous and intramuscular neridronate, respectively, achieved a therapeutic response [defined as normalization of alkaline phosphatase (ALP) levels or a reduction of at least 75% in total ALP excess]. The response to treatment was significantly correlated with baseline ALP and 25-hydroxyvitamin D [25(OH)D] levels at 6 months. The decrease in ALP levels was highest in patients with higher baseline total or bone-specific ALP levels and with higher 25(OH)D levels at 6 months. Response rates were maintained at 12 months but decreased progressively at 24 and 36 months without significant differences between the two neridronate regimens. Both regimens were well tolerated. The only relevant side effect was an acute-phase response occurring in 14% of the patients. In conclusion, these results indicate that a 200-mg intramuscular neridronate course has a similar efficacy as an intravenous infusion of the same dose for the treatment of PDB and might be of particular value for patients intolerant to oral bisphosphonates and unwilling or unable to undergo intravenous infusions.