Weekly Fosamax vs. Actonel over two years
J Clin Endocrinol Metab. 2006 Apr 24; [Epub ahead of print], Bonnick S and others. PMID: 166361120 This is a very interesting comparison of weekly treatments with either Fosamax or Actonel in postmenopausal osteoporosis over a two-year period. There was a total of 1053 women in the study during the first year. 833 of these women continued into a second year of therapy with either 70 mg alendronate (Fosamax) or 35 mg risedronate (Actonel). Of the various factors compared, results showed alendronate produced greater increases from baseline in BMD (bone mineral density) at the trochanter and all other sites tested at 24 months compared to risedronate. There were significantly more alendronate than risedronate patients with BMD increases of >/=0% and >/=3% at all BMD sites and fewer alendronate patients had measured decreases of >/=3% at all BMD sites. There were also greater reductions in all biochemical markers of bone turnover with alendronate than with risedronate. As well there were no differences in occurrence or discontinuations due to upper gastrointestinal adverse events. The authors concluded: “Patients receiving OW (once weekly) alendronate 70 mg had greater gains in BMD, were more likely to maintain or gain BMD, and had greater reductions in bone turnover markers than patients receiving OW risedronate 35 mg after 24 months, with no differences in upper gastrointestinal tolerability.” Editor's comments: This article has a free online full copy available by clicking on the link when viewing the abstract. I like to read the full article if possible, and especially to read the discussion. That segment often has little jewels that you don't pick up when reading any other segment of the article or the abstract. So you might want to click on the full article and read it for yourself. Here are a few of the salient points that I spotted in the discussion:
“The BMD treatment differences appeared to diverge over time. . .” This would indicate that the longer the therapy, the more improved are the results when comparing alendronate to risedronate.
They authors point out that, “Women treated with risedronate were 1.2 to 1.3 times more likely to show a measured decrease in BMD than those treated with alendronate. This ratio became more pronounced when the proportion of women losing 3% or more were compared between the two treatment groups.” So, for some reason, there is a greater percentage of women who take risedronate that don't respond to therapy and actually continue to lose BMD. The authors note the importance of gain in BMD is due to the fact that there is decreased risk of fracture for women taking risedronate when they show an improvement in BMD compared to those women who lose BMD while on risedronate therapy. Thus, loss of BMD while on risedronate means greater risk of fracture.
Bottom line: Fosamax won out for every variable measured in this study, or, as was the case for adverse events, there was no difference between the two agents. I'm not sure the difference was great enough to want to change from risedronate to alendronate, but if you are just starting treatment, this study might sway you toward using Fosamax to get maximum gains from therapy.