Response to therapy with once-weekly alendronate 70 mg compared to once-weekly risedronate 35 mg in the treatment of postmenopausal osteoporosis.

OBJECTIVE: The FACT study (Fosamax Actonel Comparison Trial) was a 1-year-head-to-head trial comparing the efficacy and tolerability of once weekly (DW) alendronate 70 mg and OW risedronate 35 mg for the treatment of postmenopausal osteoporosis. The present analysis was performed to determine the percentage of patients who had changes during the study in BMD and biochemical markers (BCMs) of bone turnover above or below specific cut-off points. A subgroup analysis of upper gastrointestinal (UGI) tolerability was also performed.

RESEARCH DESIGN AND METHODS: 1053 postmenopausal women with low BMD were randomized to alendronate 70 mg OW (N = 520) or risedronate 35 mg OW (N = 533). The percentage of patients who had measured BMD gains > or = 3%, and > or = 5% after 12 months at the hip trochanter, total hip, femoral neck, and lumbar spine (LS) was analyzed. The percentage of patients who experienced any bone loss, and those with measured losses of 3% or more at these sites after 12 months, was determined. The percentage of patients achieving reductions in urinary N-telopeptide of type 1 human collagen (NTX) > or = 40%, and serum C-telopeptide of type 1 collagen (CTx) > or = 60%, bone-specific phosphatase (BSAP) > or = 30%, and N terminal propeptide of type 1 procollagen (P1NP) > or = 50% at 3 months and 12 months was also determined. Tolerability, based on adverse experience reporting, was evaluated in a subgroup of patients with history of UGI disorders at baseline.

RESULTS: A greater percentage of alendronate- than risedronate-treated patients had measured BMD gains (> or = 0%) (p < 0.05) at all sites at 12 months. Significantly more (p < 0.01) alendronate- than risedronate-treated patients had measured gains in BMD > or = 3% and > or = 5% at the hip trochanter, total hip, and LS spine. Significantly more (p < 0.05) risedronate- than alendronate-treated patients had an apparent loss of BMD (> 0% and > or = 3% loss) at the same sites. After 3 months, significantly (p < 0.001) more alendronate- than risedronate- treated patients achieved predefined reductions in all BCMs. Similar tolerability was demonstrated in both treatment groups, regardless of whether or not patients had a history of UGI disorders at baseline.

CONCLUSIONS: Significantly more alendronate- than risedronate-treated patients achieved predefined increases in BMD at 12 months and reductions in BCMs at 3 months. Significantly more risedronate- than alendronate-treated patients were classified as apparent 'non-responders' (i.e. experienced any bone loss) after 12 months of therapy. The tolerability profiles of the two medications were similar.