Clinical Efficacy on Fracture Risk and Safety of 0.5 mg or 1 mg/month Intravenous Ibandronate Versus 2.5 mg/day Oral Risedronate in Patients with Primary Osteoporosis

This randomized, double-blind study assessed the antifracture efficacy and safety of intermittent intravenous (IV) ibandronate versus oral daily risedronate in Japanese patients with primary osteoporosis. Ambulatory patients aged ≥60 years were randomized to receive 0.5 or 1 mg/month IV ibandronate plus oral daily placebo or 2.5 mg/day oral risedronate, the licensed dose in Japan, plus IV placebo. The primary end point was noninferiority of ibandronate versus risedronate for first new or worsening vertebral fracture over 3 years. A total of 1,265 patients were randomized. A total of 1,134 patients formed the per-protocol set. Both ibandronate doses were noninferior to risedronate: 0.5 mg, hazard ratio (HR) 1.09 [95 % confidence interval (CI) 0.77–1.54]; 1 mg, HR 0.88 (95 % CI 0.61–1.27). The rate of first new vertebral fracture over 3 years was 16.8 % (95 % CI 12.8–20.8) for 0.5 mg ibandronate, 11.6 % (95 % CI 8.2–15.0) for 1 mg ibandronate, and 13.2 % (95 % CI 9.6–16.9) for risedronate. Significant increases in bone mineral density relative to baseline were observed with all treatments after 6 months, with substantial reductions in bone turnover markers after 3 months. Greatest efficacy was obtained with 1 mg ibandronate. Analyses in women only showed similar results to the overall population. No new safety concerns were identified. This study demonstrated the noninferiority of IV ibandronate to the licensed Japanese dose of oral risedronate and suggested that 1 mg/month is an effective dose in Japanese patients with primary osteoporosis.