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Variation in the days supply field for osteoporosis medications in Ontario

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Abstract

Summary

We examined pharmacy claims for osteoporosis medications dispensed in the community (78 %) and long-term care (LTC) to determine if days supply values matched expected dosing intervals. Results identify potential reporting errors that can have implications for drug exposure misclassification, particularly in LTC where only 59 % of reported values matched expected values.

Introduction

The days supply field is commonly used to examine patterns of drug utilization and classify drug exposure, yet its accuracy has received little attention. We sought to describe the days supply reported for osteoporosis drugs and examine if values matched expected therapeutic dosing intervals.

Methods

We examined days supply values for osteoporosis medications submitted to the Ontario Drug Benefits program for seniors, 1997–2011. Days supply values were evaluated by dosing regimen and setting (community or long-term care [LTC]) and compared to pre-defined expected values. We defined expected days supply by the therapeutic dosing interval: daily in 7- or 30-day intervals, or as 100 days; weekly in 7- or 30-day intervals; monthly and daily nasal spray in 28- or 30-day intervals; and cyclical etidronate as a 90-day supply.

Results

We identified 17,615,404 osteoporosis prescriptions, with 78 % dispensed in the community. Most daily oral prescriptions were dispensed by an expected therapeutic dosing interval (97 %). Annual IV zoledronic acid was most commonly dispensed as a 1-day supply (62 %). Distinct differences in agreement were observed for other regimens, with the expected days supply more commonly reported in community versus LTC: cyclical etidronate (86 % vs. 40 %), weekly (91 % vs. 60 %), monthly (94 % vs. 35 %), and nasal spray (84 % vs. 40 %).

Conclusions

Results suggest that inaccuracies in the days supply field exist, particularly among prescriptions dispensed in LTC. Inaccurate reporting may have significant implications for osteoporosis drug exposure misclassification.

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Acknowledgments

This research was supported by research grants to Dr. Cadarette from the Canadian Institutes of Health Research (CIHR, DSA-10353) and the Ontario Ministry of Research and Innovation (OMRI, Early Researcher Award ER09-06-043). Dr. Cadarette is supported by a CIHR New Investigator Award in Aging and Osteoporosis (MSH-95364), Andrea Burden is supported by Ontario Graduate Scholarships for doctoral research, and Mina Tadrous is supported by a CIHR Doctoral Award—Frederick Banting and Charles Best Canada Graduate Scholarship (GSD-11342). Authors acknowledge Brogan Inc. for providing access to drug identification numbers used to identify eligible drugs and Usama El-Bbayoumi, PharmD, for insightful discussions about LTC pharmacy. The Institute for Clinical Evaluative Sciences (ICES) is a non-profit research corporation funded by the Ontario Ministry of Health and Long-Term Care. As a Prescribed Entity under Ontario's privacy law (Section 45 of the Personal Health Information Protection Act and Regulation 329/04, Section 18), ICES is legally permitted to receive and use personal health information for health services research. To have this privilege, ICES maintains policies, practices, and procedures that are approved and regularly audited by the Information and Privacy Commissioner of Ontario (www.ipc.on.ca). The opinions, results, and conclusions are those of the authors and are independent from the funding sources. No endorsement by CIHR, ICES, OMRI, or the Ontario Ministry Health and Long-Term Care is intended or should be inferred.

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Authors and Affiliations

  1. Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada

    Andrea M. Burden, Mina Tadrous & Suzanne M. Cadarette

  2. Institute for Clinical Evaluative Sciences, Toronto, ON, Canada

    Anjie Huang & Suzanne M. Cadarette

  3. Leslie L. Dan Pharmacy Building, University of Toronto, 144 College Street, Toronto, ON, M5S 3M2, Canada

    Suzanne M. Cadarette

Authors
  1. Andrea M. Burden
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  2. Anjie Huang
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  3. Mina Tadrous
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  4. Suzanne M. Cadarette
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Corresponding author

Correspondence to Suzanne M. Cadarette.

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Burden, A.M., Huang, A., Tadrous, M. et al. Variation in the days supply field for osteoporosis medications in Ontario. Arch Osteoporos 8, 128 (2013). https://doi.org/10.1007/s11657-013-0128-1

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