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.


BACKGROUND
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.


METHODS
The study was done on primary and secondary prevention cohorts from the Régie de l'assurance maladie du Québec (Québec). 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.


RESULTS
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.


CONCLUSIONS
This study confirms that poor adherence to oral BPs leads to a significant waste of money and avoidable fractures.
Sheehy
O
O
Pharmacoeconomics and Pharmacoepidemiology, Centre hospitalier de l'Université de Montréal, Montreal, Quebec, Canada. odile.sheehy@umontreal.ca
Kindundu
C
C
Barbeau
M
M
LeLorier
J
J
D000284:Administration, Oral; D000368:Aged; D000369:Aged, 80 and over; D050071:Bone Density Conservation Agents / Q000191:economics / Q000627:therapeutic use*; D004164:Diphosphonates / Q000191:economics / Q000627:therapeutic use*; D016527:Drug Costs; D005260:Female; D050723:Fractures, Bone / Q000191:economics / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000188:drug therapy* / Q000191:economics / Q000453:epidemiology; D011792:Quebec / Q000453:epidemiology; D012189:Retrospective Studies; D018570:Risk Assessment; D016903:Drug Monitoring
D050071:Bone Density Conservation Agents; D004164:Diphosphonates