The Effect of Effervescent and Buffered Alendronate Compared to Conventional Alendronate on Markers of Bone Turnover: A Randomized Non-inferiority Trial

Buffered and effervescent alendronate (ALN-EFF) increases gastric pH and is reported to decrease the risk of gastrointestinal side effects compared to conventional formulations of alendronate (ALN). The clinical effectiveness of ALN-EFF, however, has not been investigated. This study aims to investigate if ALN-EFF is non-inferior to ALN in suppressing bone turnover markers (BTM). We conducted a 16-week prospective, randomized, open-label study comprising 64 postmenopausal women with BMD T-score < −1 naïve to osteoporosis treatment. Participants were randomized 1:1 to ALN or ALN-EFF. We collected blood samples at 0, 4, 8, and 16 weeks. Non-inferiority margin was determined as 12% (80% of efficacy retained), and an SD of 15% on change in CTx. CTx decreased by 58.2% ± 24.1% in the ALN group and by 46.9% ± 23.3% (CI − 38.42:− 55.35) in the ALN-EFF group (p = 0.08). The non-inferiority limit was 46.6%. With ALN-EFF the CI crosses the non-inferiority limit thus the test for non-inferiority was indeterminate. PINP decreased by 45.7 ± 22.6% in the ALN group and by 35.1 ± 20.7% in the ALN-EFF group (p = 0.07). Changes over time in the BTMs were not significantly different between the groups, p > 0.10 for both CTx and PINP. There was no difference in frequency of AEs or compliance between the two groups, but rate of discontinuation was lower with ALN-EFF. In conclusion, suppression of BTMs was not significantly different between the groups but formal non-inferiority could not be established.