Weekly alendronate versus risedronate for postmenopausal osteoporosis-is there a difference?

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Abstract

BACKGROUND

Alendronate and risedronate are widely used to treat postmenopausal osteoporosis. A trial (FACT) assessed the efficacy of weekly doses of these agents over a 12-month period. Although both drugs conferred clinical benefits, alendronate seemed to be a more potent antiresorptive agent than risedronate.

OBJECTIVE

To perform a 12-month extension of FACT to determine whether the effects of alendronate on BMD and bone markers are maintained.

DESIGN AND INTERVENTION

FACT was a randomized, double-blind, multicenter study. Postmenopausal women aged ≥40 years (or ≥25 years if surgically menopausal) with osteoporotic BMD scores at one or more sites were enrolled. Exclusion criteria included hypocalcemia, hypovitaminosis D, and metabolic bone disease other than osteoporosis. Participants received 70 mg oral alendronate or 35 mg oral risedronate weekly for the entire study period. Additionally, all participants consumed 1000 mg calcium and 400 IU vita min D daily from their diet or as supplements. BMD at the hip trochanter, total hip, femoral neck, and lumbar spine was measured by dual energy X-ray absorptiometry. Bone resorption was evaluated by measurement of urinary N-telopeptide of type I human collagen and serum C-telopeptide, whereas bone-specific alkaline phosphatase and serum N-terminal propeptide of type 1 procollagen were assessed as markers of bone formation.

OUTCOME MEASURES

The primary outcome measure was the mean percentage change from baseline in hip trochanter BMD. Secondary measures included the mean percentage change in BMD at other sites, the mean percentage change in markers of bone turnover, and the incidence of adverse events.

RESULTS

A total of 833 women were enrolled in the extension study. At study end, BMD increases from baseline were greater at all sites with alendronate than risedronate (P<0.001). The treatment differences at month 24 were 2.1% (hip trochanter), 1.7% (total hip), 1.9% (femoral neck), and 1.8% (lumbar spine). Differences increased with time at all four sites. Of the patients treated with alendronate, more participants gained or maintained BMD at each site than in the risedronate group. A BMD gain ≥3% was 1.4-1.7 times more likely with alendronate than risedronate. Conversely, patients treated with risedronate were 2-4 times more likely to have a BMD decrease ≥3% than those treated with alendronate. Although both treatments reduced bone resorption, alendronate was more effective than risedronate (treatment difference at 24 months was 13%). This difference was significant at 3 months and maintained at 24 months (P<0.001). A similar trend was observed for the bone formation markers (treatment difference at 24 months was 11%, P<0.001). There was no difference in the incidence or severity of adverse events, which included gastrointestinal symptoms, or in discontinuations from adverse events. The proportion of patients who reported fractures was also similar.

CONCLUSION

Weekly alendronate remained a more potent antiresorptive agent than weekly risedronate after 24 months of treatment.

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