ECTS Abstracts (2015) 1 P361

Uptake and characteristics of zoledronic acid and denosumab patients and physicians in ontario, canada: impact of drug formulary access

Andrea Burden1,2, Mina Tadrous1, Andrew Calzavara3, Yannick Nielen2,4, Frank de Vries2,4 & Suzanne Cadarette1,3


1Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada; 2Department of Clinical Pharmacy and Toxicology, Maastricht University, Maastricht, The Netherlands; 3Institute for Clinical Evaluative Sciences, Toronto, Canada; 4Care and Public Health Research Institute, Maastricht, The Netherlands.


Background: We sought to describe the use of zoledronic acid and denosumab by physicians and patients over time, and examine the impact of a 2012 provincial formulary modification that removed prescribing restrictions for zoledronic acid.

Methods: We identified users of zoledronic acid and denosumab using Ontario pharmacy claims data. The number of new patients and physicians were plotted and examined over time. Interrupted time-series analysis examined the impact of a formulary modification to zoledronic acid. Descriptive characteristics of patients and prescribers were summarised pre- and post-formulary change for zoledronic acid and overall for denosumab.

Results: We identified 1,463 zoledronic acid users treated by 627 physicians and 16,736 denosumab users treated by 2,904 physicians. In the first two months on the market, we identified a rapid uptake of denosumab (>450 new physicians and >1,200 new patients) in contrast to zoledronic acid (<10 new physicians and <10 new patients). Zoledronic acid use increased significantly in the two months post-formulary change with >80 new physicians and >200 new patients. Prior to the formulary change, more zoledronic acid users had a history of osteoporosis therapy (41% vs. 26%) or bone density testing (30% vs. 10%). Compared with zoledronic users initiating after the formulary change, more denosumab users had prior osteoporosis therapy (55% vs. 26%), yet fewer had a gastrointestinal diagnosis (6% vs. 11%).

Conclusion: We identified a rapid uptake of denosumab in only 15 months of observation. A provincial formulary modification removing administrative burden on physicians prescribing zoledronic acid resulted in an increase in utilisation and impacted patient characteristics.

Disclosure: The authors declared no competing interests.

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