Efficacy and acceptability of risedronate 5 mg daily compared with 35 mg once weekly for the treatment of postmenopausal osteoporosis.

OBJECTIVE: Risedronate is a bisphosphonate used in the treatment of osteoporosis. It has a strong effect in inhibiting osteoclast activity. The primary objective of this study was to evaluate the effectiveness and adverse events of two different forms of risedronate (5 mg and 35 mg) using a rapid biochemical marker for comparison of C-terminal telopeptide (CTx) type I collagen cross-links. METHODS: The study was designed at Bakirkoy Dr. Sadi Konuk Education & Research Hospital, between January and June 2004. A total of 123 postmenopausal osteoporotic women were randomly assigned in blocks of three to one of the following groups: control, risedronate 5 mg/day and risedronate 35 mg once a week. RESULTS: Of the 123 women enrolled, 103 (83.7%) completed the study. Adverse events were experienced by 53.6% in the control group, 56% in the risedronate 5 mg/day group and 53.6% in the group receiving risedronate 35 mg once per week. The most common adverse events were gastrointestinal (21.9% of subjects in group 1, 29.2% of subjects in group 2, 24.3% of subjects in group 3). The women in groups receiving risedronate either 5 mg/day and 35 mg once per week had similarly decreased levels of CTx but the control group was not as effective. CONCLUSION: The results support the hypothesis that risedronate 35 mg given once per week has the same therapeutic efficacy and safety as a daily 5 mg regimen. Taking the medicine once a week is likely to be easier and more satisfactory than the daily regimen. However, patients taking a once-a-week regimen may forget to take it due to the 7-day break without medicine.