Intramuscular clodronate in nonresponders to oral alendronate therapy for osteoporosis

Objective, Oral alendronate is effective in increasing bone mineral density (BMD) and in reducing fracture incidence. However, a large proportion of p atients under treatment do not show significant changes in BMD, or even bon e loss. Incorrect administration, low intestinal absorption, and poor compl iance are among factors that may account for this effect. In this subgroup of patients we evaluated whether intramuscular (im) clodronate increased th e number of responders. Methods. Using an open case-control design we studied 60 postmenopausal ost eoporotic women (mean age 58.9 years +/- 4.8 SD) after one year of therapy with oral alendronate who had an increase in BMD that was lower than the in vivo densitometry measurement error (2%). Subjects were divided into 2 gro ups: the first continued aledronate treatment (AL group); the second began weekly im injections of clodronate 100 mg (CL group). BMD measurements were performed at the right Femoral neck by the same operator, using dual energ y x-ray absorptiometry. Results. After 12 months of therapy the prevalence of responders (increase in BMD > 2%) was 40% in the AL group and 66% in the CL group (prevalence ra te ratio = 1.65; 95% CI 1.25-2.04). The treatment group was the only variab le that showed a significant correlation with being a responder (beta = 1.1 3; p = 0.03), as analyzed by multiple logistic regression to account for th e effect of confounding factors. In the CL group the difference in the mean value of BMD between time TO and time T+12. was greater than in the AL gro up, bur did nor reach statistical significance. The mean percentage variati on of BMD was significantly greater in the CL group (+3.21%) compared to th e AL group (+0.98%) (p < 0.001, t test) (f value = 8.4: p < 0.01, by multip le linear regression analysis using the same covariates). Conclusion, Treatment with weekly intramuscular injection of clodronate in nonresponders to oral alendronate showed a higher number of subjects with a significant increase in BMD, compared to continuation of therapy with alen dronate.