Seven Years of Treatment with Risedronate in Women with Postmenopausal Osteoporosis

The effects of 7 years of risedronate treatment were evaluated in a second 2-year extension of a 3-year vertebral fracture study in women with osteoporosis. For the first 5 years of the study, women received risedronate 5 mg/day or placebo according to the original randomization, with maintenance of blinding. All the women who entered into the 6–7 years extension study received risedronate 5 mg/day. Endpoints included vertebral and nonvertebral fracture assessments, changes in biochemical markers of bone turnover, and bone mineral density (BMD) measurements. A total of 164 women (placebo/risedronate group, 81; risedronate group, 83) entered the 6–7 years extension study and 136 (83%) completed the study. Annualized incidence of new vertebral fractures during the 6–7 years was similar between the 2 treatment groups (3.8%). The incidence of vertebral fractures did not change in the 7-year risedronate group during the 6–7 years as compared to 4–5 years, while a significant reduction was observed in the placebo group that switched to risedronate treatment during years 6–7. The incidence of nonvertebral fractures was 7.4% and 6.0% in the placebo/risedronate and risedronate groups, respectively, during years 6–7. Urinary N-telopeptide decreased from baseline by 54% and 63% at 3 months and 7 years, respectively, in the risedronate group. The increases in BMD from baseline after 5 years of risedronate treatment were maintained or increased further during years 6–7; lumbar spine BMD after 5 and 7 years of risedronate treatment increased from baseline by 8.8% and 11.5%, respectively, for this extension study population. Risedronate was well tolerated and the occurrence of upper gastrointestinal adverse events was low. After 7 years of continuous risedronate treatment there were significant increases in BMD and decreases in bone turnover to within premenopausal levels and there was no indication of any loss of anti-fracture efficacy.