Adherence to weekly oral bisphosphonate therapy: cost of wasted drugs and fractures

In an observational cohort of patients treated with biphosphonates (BP), we observed that poor adherence to these drugs causes important expenditures in terms of avoidable fractures. Of particular interest are the amounts of money wasted by patients who did not take their BPs long enough to obtain a clinical benefit. A large proportion of patients initiated with oral weekly BP therapy stop their treatment within the first year. The objective of this study was to estimate the impact of the poor adherence to BPs in terms of drug wasted and avoidable fractures. The study was done on primary and secondary prevention cohorts from the R,gie de l'assurance maladie du Qu,bec (Qu,bec). The concept of the point of visual divergence was used to determine the amount of wasted drug. The risk of fracture was estimated using Cox regression models. The hazard ratios of compliant patients (+80%) versus non compliant patients were used to estimate the number of fractures saved. The cost of wasted drugs was $25.87 per patient initiated in the primary prevention cohort and $30.52 in the secondary prevention cohort. If all patients had been compliant, 110 fractures would have been avoided in the primary prevention cohort and 19 fractures in the secondary prevention cohort. The cost of these avoidable fractures per patient initiated on BP therapy was $62.95 in primary prevention cohort and $330.84 in secondary prevention cohort. This study confirms that poor adherence to oral BPs leads to a significant waste of money and avoidable fractures.