To demonstrate the clinical benefit of
risedronate at 2.5 mg daily in the treatment of involutional
osteoporosis, the effect of
risedronate on incidence of vertebral fracture was compared with that of
etidronate. A total of 547 patients with one to four vertebral fractures were randomized to receive either treatment with 2.5 mg/day of
risedronate or intermittent treatment (treatment of 2 weeks and off period of 10 weeks) with 200 mg/day of
etidronate for 96 weeks in a double-masked fashion. All patients received 200 mg
calcium supplement daily. Lateral and anteroposterior thoracic and lumbar spine radiographs were obtained at baseline and at 24, 48, 72, and 96 weeks. Cumulative incidence rates of patients who had at least one new or worsening vertebral fracture during the 96-week period were 12.3% for
risedronate and 14.2% for
etidronate, and it was verified that the fracture prevention effect of
risedronate was not inferior to that of
etidronate. The incidence rates of fracture during the initial 24-week period were 8.8% for
risedronate and 6.0% for
etidronate, but the cumulative incidence rate of fracture from 24 to 96 weeks was lower in the
risedronate group (3.9%) as compared to the
etidronate group (8.7%). Height loss was significantly less in the
risedronate group (-0.28 cm) than in the
etidronate group (-0.70 cm) after 96 weeks. Decreases in
bone resorption markers including urinary total
deoxypyridinoline and NTX were significantly greater in the
risedronate group than in the
etidronate group throughout the treatment period. An improvement of patient QOL was observed in both groups. No significant difference in the incidence of adverse events was observed between the two treatments. Daily oral
risedronate (2.5 mg) was shown to provide an effective
therapy for involutional
osteoporosis in Japanese patients with good tolerability.