Osteoporosis medication prescribing in British Columbia and Ontario: impact of public drug coverage

Methodological guidance for the use of real-world data to measure exposure and utilization patterns of osteoporosis medications

Observational studies of osteoporosis medications can provide critical real-world evidence (RWE) that fills knowledge gaps left by clinical trials. However, careful consideration of study design is needed to yield reliable estimates of association. In particular, obtaining valid measurements of exposure to osteoporosis medications from real-world data (RWD) sources is complicated due to different medication classes, formulations, and routes of administration, each with different pharmacology. Extended half-lives of bisphosphonates and extended dosing of denosumab and zoledronic acid require particular attention. In addition, prescribing patterns and medication taking behavior often result in gaps in therapy, switching, and concomitant use of osteoporosis therapies. In this review, we present important considerations and provide specialized guidance for measuring osteoporosis drug exposures in RWD. First, we compare different sources of RWD used for osteoporosis drug studies and provide guidance on identifying osteoporosis medication use in these data sources. Next, we provide an overview of osteoporosis pharmacology and how it can influence decisions on exposure measurement within RWD. Finally, we present considerations for the measurement of osteoporosis medication exposure, adherence, switching, long-term exposures, and drug holidays using RWD. Ultimately, a thorough understanding of the differences in RWD sources and the pharmacology of osteoporosis medications is essential to obtain valid estimates of the relationship between osteoporosis medications and outcomes, such as fractures, but also to improve the critical appraisal of published studies.

Commentary: Zebrafish as a Model for Osteoporosis-An Approach to Accelerating Progress in Drug and Exercise-Based Treatment

Osteoporosis (OP) is a degenerative disease characterized by reduced bone strength and increased fracture risk. As the global population continues to age, the prevalence and economic burden of osteoporosis can be expected to rise substantially, but there remain various gaps in the field of OP care. For instance, there is a lack of anti-fracture drugs with proven long-term efficacy. Likewise, though exercise remains widely recommended in OP prevention and management, data regarding the safety and efficacy for patients after vertebral fracture remain limited. This lack of evidence may be due to the cost and inherent difficulties associated with exercise-based OP research. Thus, the current research landscape highlights the need for novel research strategies that accelerate OP drug discovery and allow for the low-cost study of exercise interventions. Here, we outline an example of one strategy, the use of zebrafish, which has emerged as a potential model for the discovery of anti-osteoporosis therapeutics and study of exercise interventions. The strengths, limitations, and potential applications of zebrafish in OP research will be outlined.

Over half of seniors who start oral bisphosphonate therapy are exposed for 3 or more years: novel rolling window approach and patterns of use

Most adherence studies only consider treatment following a first prescription. Using an extended follow-up, we found that 60% of seniors starting oral bisphosphonate therapy were exposed for ≥ 3 years (48% for ≥ 5 years). Studies are needed to examine the benefits and harms of continuing bisphosphonate therapy beyond 3 years.

INTRODUCTION

The purpose of this study was to identify and describe patterns of long-term oral bisphosphonate use among seniors using a novel methodological approach that considers extended follow-up.

METHODS

Among Ontarians aged 66 years or older, we identified subjects with a first dispensing of alendronate or risedronate between November 2000 and December 2016. We followed them until death or December 2019 to identify patients with ≥ 3 years of bisphosphonate use, defined as a proportion of days covered ≥ 80%, using 3-year rolling windows. We calculated the proportion of patients with long-term therapy (≥ 3 years of use) using Kaplan-Meier estimates. We described patterns of long-term use and compared patient characteristics between patients with and without long-term therapy.

RESULTS

We identified 260,784 eligible seniors initiating bisphosphonate therapy. Of these, 60% continued therapy ≥ 3 years (77% women), and 48% continued ≥ 5 years. Characteristics did not meaningfully differ between patients with or without long-term therapy. The median length of long-term therapy was 7.0 (IQR 5.1) years for women and 6.1 (IQR 4.3) years for men. Only 20% experienced a treatment gap before long-term therapy, yet 50% experienced a treatment gap of ≥ 120 days after a median 5.3 years of therapy. Eighty-one percent who returned to therapy following a treatment gap re-initiated an oral bisphosphonate, with 18% switching to denosumab.

CONCLUSIONS

Among seniors initiating oral bisphosphonates, we found that 60% receive at least 3 years of therapy when using an extended follow-up. Studies are needed to examine the benefits and harms of continuing bisphosphonate therapy beyond 3 years.

Use of an electronic medical record dashboard to identify gaps in osteoporosis care

Using an electronic medical record (EMR)-based dashboard, this study explored osteoporosis care gaps in primary care. Eighty-four physicians shared their practice activities related to bone mineral density testing, 10-year fracture risk calculation and treatment for those at high risk. Significant gaps in fracture risk calculation and osteoporosis management were identified.

PURPOSE

To identify care gaps in osteoporosis management focusing on Canadian clinical practice guidelines (CPG) related to bone mineral density (BMD) testing, 10-year fracture risk calculation and treatment for those at high risk.

METHODS

The ADVANTAGE OP EMR tool consists of an interactive algorithm to facilitate assessment and management of fracture risk using CPG. The FRAX® and Canadian Association of Radiologists and Osteoporosis Canada (CAROC) tools were embedded to facilitate 10-year fracture risk calculation. Physicians managed patients as clinically indicated but with EMR reminders of guideline recommendations; participants shared practice level data on management activities after 18-month use of the tool.

RESULTS

Eighty-four physicians (54%) of 154 who agreed to participate in this study shared their aggregate practice activities. Across all practices, there were 171,310 adult patients, 40 years of age and older, of whom 17,214 (10%) were at elevated risk for fracture. Sixty-two percent of patients potentially at elevated risk for fractures did not have BMD testing completed; most common reasons for this were intention to order BMD later (48%), physician belief that BMD was not required (15%) and patient refusal (20%). For patients with BMD completed, fracture risk was calculated in 29%; 19% were at high risk, of whom 37% were not treated with osteoporosis medications as recommended by CPG.

CONCLUSION

Despite access to CPG and fracture risk calculators through the ADVANTAGE OP EMR tool, significant gaps remain in fracture risk calculation and osteoporosis management. Additional strategies are needed to address this clinical inertia among family physicians.

Time trends in oral bisphosphonate initiation in Ontario, Canada over 20 years reflect drug policy and healthcare delivery changes

Characteristics of patients starting oral bisphosphonate therapy changed over time, reflecting trends in osteoporosis management (e.g., new drugs to market), and general healthcare delivery (e.g., benzodiazepine use declined, statin use increased). When designing studies that examine osteoporosis drug effects, potential time-related biases must be considered.

INTRODUCTION

To describe the type of oral bisphosphonate initiated and characteristics of patients starting oral bisphosphonate therapy over time.

METHODS

We identified community-dwelling older adults (ages ≥ 66 years) initiating oral bisphosphonate therapy from April 1996 to March 2016 (1996 to 2015 fiscal years) using healthcare administrative data in Ontario. Patients with conditions other than osteoporosis that may impact bisphosphonate prescribing were excluded. The bisphosphonate initiated and patient characteristics were summarized by fiscal year and stratified by sex.

RESULTS

We identified 560,817 eligible patients (81% women). Most patients initiated cyclical etidronate from 1996 until 2005, and then weekly regimens became dominant. In 2008, risedronate became the main oral bisphosphonate (46% risedronate, 43% alendronate, 11% etidronate); with its use increasing after availability of monthly and delayed-release risedronate formulations. In 2015, 71% of patients started risedronate, 28% started alendronate, and less than 2% started etidronate. Characteristics of patients changed over time, reflecting changes in osteoporosis management and general healthcare delivery. Over time, a larger proportion of men (9% to 28%) and patients with diabetes (women 10% to 17%, men 14% to 22%) initiated therapy; benzodiazepine (women 22% to 13%, men 20% to 10%) and estrogen-based hormone replacement therapy (12% to 15% of women 1996-2002 to 3% since 2008) decreased, while statin use increased (women 15% to 39%, men 14% to 52%).

CONCLUSIONS

The characteristics of patients starting oral bisphosphonate therapy have changed over time. Consideration must be given to these time trends when designing studies that examine osteoporosis drug effects.

Denosumab and breast cancer risk in postmenopausal women: a population-based cohort study

BACKGROUND

Denosumab inhibits the receptor activator of nuclear factor κB (RANK) pathway and is used to treat osteoporosis. Emerging evidence suggests RANK-blockade may play a role in mammary tumourigenesis. Thus, we undertook a population-based study of denosumab use and breast cancer risk in a large cohort of postmenopausal women.

METHODS

We included women 67+ years with prior bisphosphonate use who filled a first prescription for denosumab. They were matched on age, date, cumulative prior use of and time since last use of a bisphosphonate to women with no history of denosumab. Cox proportional hazards was used to estimate the hazard ratio (HR) of breast cancer with denosumab use.

RESULTS

A total of 100,368 women were included in the analysis with 1271 incident breast cancer events. Denosumab use was associated with a 13% decreased breast cancer risk (HR = 0.87; 95% CI 0.76-1.00). There was no relationship between increasing number of denosumab doses and breast cancer risk (P-trend = 0.15).

CONCLUSION

These findings suggest a potential protective effect of ever denosumab use on breast cancer risk in a cohort of older women previously treated with bisphosphonates.

Effectiveness of Oral Bisphosphonates in Reducing Fracture Risk Among Oral Glucocorticoid Users: Three Matched Cohort Analyses

The benefit of oral bisphosphonates in reducing fracture risk in glucocorticoid-induced osteoporosis is controversial. We aimed to estimate the effectiveness of oral bisphosphonates in reducing fracture risk in a cohort of new chronic oral glucocorticoid users. We created three matched cohorts using health care administrative data from Ontario, Canada. We included residents aged 66 years and older initiating chronic oral glucocorticoids (≥450 mg prednisone equivalent and ≥2 glucocorticoid prescriptions within a 6-month window) between January 1998 and September 2014. Exposed patients were those who initiated an oral bisphosphonate (alendronate, etidronate, or risedronate) within the first 6 months of starting chronic oral glucocorticoid therapy. Exposed cohorts (3945 alendronate, 5825 risedronate, and 8464 etidronate) were each matched 1:1 to unexposed patients on glucocorticoid exposure, fracture risk factors, and propensity score. We examined incident hip (primary outcome), vertebral, forearm, and humerus fractures using Cox proportional hazard models. Alendronate (hazard ratio [HR] = 0.46, 95% confidence interval [CI] 0.25-0.80) and risedronate (HR = 0.58, 95% CI 0.36-0.90) were associated with reduced hip fracture risk. Alendronate (HR =  0.52, 95% CI 0.39-0.68), etidronate (HR = 0.59, 95% CI 0.48-0.73) and risedronate (HR = 0.47 95% CI 0.36-0.60) were associated with reduced vertebral fracture risk. No risk reduction in forearm or humerus fractures was apparent for any bisphosphonate. Among older chronic glucocorticoid initiators, all oral bisphosphonates reduced vertebral fracture risk, yet only alendronate and risedronate reduced hip fracture risk. Results were similar between men and women. We provided compelling evidence that early initiation of oral bisphosphonates during chronic oral glucocorticoid therapy is beneficial to prevent osteoporotic fractures. © 2017 American Society for Bone and Mineral Research.

Persistence with denosumab and zoledronic acid among older women: a population-based cohort study

Persistence to denosumab or zoledronic acid was increased compared to oral bisphosphonates.

INTRODUCTION

Denosumab and zoledronic acid are alternative therapies to oral bisphosphonates. Few studies have assessed persistence of those agents.

METHODS

Incident users of denosumab and zoledronic acid were identified using healthcare databases of public drug insurance plan of Quebec province, Canada. Patients initiating therapy between October 1, 2008, and June 30, 2013, and aged 50 years and over were eligible. A persistence rate was assessed over a 2-year period. We assess the proportion of patients receiving the second, third, and fourth injections within a specific delay of predicted time of renewal of both agents. The predictors of non-persistence were analyzed using a Cox regression model only among women.

RESULTS

Among 12,689 incident users, 97.2 % were women. Kaplan-Meier analysis showed a slow decline of persistence after initiating zoledronic acid compared to denosumab therapy, dropping to 81.6 and 63.3 % after 1 and 2 years of follow-up using the permissive gaps of 56 days, in contrast to zoledronic acid, where persistence rate still stays at 74.8 % after 2 years of follow-up using the permissive gap of 112 days. The likelihood of non-persistence was significantly higher among new users of denosumab and zoledronic acid among older patients and year of initiation; but depression and diabetes are only predictors of non-persistence among the zoledronic group. Concomitant use of calcium and vitamin D supplements was at low level which may compromise the clinical efficacy.

CONCLUSION

The persistence rate to denosumab and zoledronic acid was higher to the published data of oral bisphosphonates. The second intention of treatment seems to target more severe patients which may more likely to be compliant.

Glucocorticoid-induced osteoporosis management among seniors, by year, sex, and indication, 1996-2012

We identified that glucocorticoid-induced osteoporosis management (bone mineral density testing or osteoporosis treatment) among seniors improved among men (2 to 23 %) and women (10 to 48 %) between 1996 and 2007, and then remained relatively stable through to 2012. Differences were also noted by indication (from a low of 21 % for respiratory conditions to a high of 41 % for rheumatic conditions).

PURPOSE

The aim of our study was to describe the proportion of chronic oral glucocorticoid (GC) users that receive osteoporosis management (bone mineral density test or osteoporosis treatment) by sex and over time.

METHODS

We identified community-dwelling older adults initiating chronic oral GC therapy in Ontario using pharmacy data from 1996 to 2012. Chronic GC use was defined as greater than or equal to two oral GC prescriptions dispensed and ≥450 mg prednisone equivalent over a 6-month period. Osteoporosis management within 6 months of starting chronic GC therapy was examined by sex, year, indication for therapy, and osteoporosis management history. Results were summarized using descriptive statistics.

RESULTS

We identified 72,099 men and 95,975 women starting chronic oral GC therapy (mean age = 74.9 years, SD = 6.5). Approximately two thirds of patients (65 %) received ≥900 mg within the 6-month chronic use window. GC-induced osteoporosis management increased from 2 to 23 % (men) and 10 to 48 % (women) between 1996 and 2007, and then remained relatively stable through to 2012. A higher proportion of patients with prior osteoporosis management were managed within 6 months (56 % men, 67 % women) of chronic GC use, compared to patients without prior management (12 % men, 23 % women). Patients with rheumatic disease were managed most commonly (41 %), and patients with respiratory conditions were managed least commonly (21 %).

CONCLUSIONS

GC-induced osteoporosis management improved significantly over time for both sexes yet remains low. Significant care gaps by sex and between clinical areas represent a missed opportunity for fracture prevention among patients requiring chronic GC therapy.

Performance of the disease risk score in a cohort study with policy-induced selection bias

AIM

To examine the performance of the disease risk score (DRS) in a cohort study with evidence of policy-induced selection bias.

METHODS

We examined two cohorts of new users of bisphosphonates. Estimates for 1-year hip fracture rates between agents using DRS, exposure propensity scores and traditional multivariable analysis were compared.

RESULTS

The results for the cohort with no evidence of policy-induced selection bias showed little variation across analyses (-4.1-2.0%). Analysis of the cohort with evidence of policy-induced selection bias showed greater variation (-13.5-8.1%), with the greatest difference seen with DRS analyses.

CONCLUSION

Our findings suggest that caution may be warranted when using DRS methods in cohort studies with policy-induced selection bias, further research is needed.

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

The addition of Limited Use criteria (less restrictive access) for zoledronic acid resulted in an immediate and significant increase in uptake and resulted in differences in patient/physician characteristics. In comparison, the uptake of denosumab (only listed with Limited Use) was rapid. Thus, formulary access restrictions have significant implications for prescribing.

INTRODUCTION

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 the administrative burden on physicians when prescribing zoledronic acid.

METHODS

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

RESULTS

We identified 1463 zoledronic acid patients treated by 627 physicians and 16,736 denosumab patients treated by 2904 physicians. In the first 2 months on the market, we identified a rapid uptake of denosumab (>450 physicians and >1200 patients) in contrast to zoledronic acid (<10 physicians and <10 patients). Zoledronic acid use increased significantly in the 2-month post-formulary change, yet no change in denosumab was observed. Prior to the formulary modification, more zoledronic acid patients had a history of osteoporosis therapy (41 vs. 26%) or bone density testing (30 vs. 10%). Compared to zoledronic patients (post-formulary modification), more denosumab patients 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 to zoledronic acid resulted in an increase in utilization and impacted patient characteristics.

Osteoporosis management and fractures in the Métis of Ontario, Canada

Half of Métis citizens, compared to less than 10 % of the general population of Ontario, reside in northern regions, with little access to bone mineral density (BMD) testing. Métis citizens had lower sex-specific and age-standardized rates of BMD testing, yet similar rates of fracture (both sexes) and pharmacotherapy (women only).

PURPOSE

To examine osteoporosis management and common osteoporosis-related fractures among Métis citizens compared to the general population of older adults residing in Ontario.

METHODS

We linked healthcare (medical and pharmacy) utilization and administrative (demographic) databases with the Métis Nation of Ontario citizenship registry to estimate osteoporosis management (bone mineral density [BMD] testing, pharmacotherapy) and fractures (hip, humerus, radius/ulna) among adults aged ≥50 years, from April 1, 2006 to March 31, 2011. Pharmacotherapy data were limited to residents aged ≥65 years. Sex-specific and age-standardized rates were compared between the Métis and the general population. Multivariable logistic regression was used to compare rates of BMD testing after controlling for differences in age and region of residence between the Métis and the general population.

RESULTS

We studied 4219 Métis citizens (55 % men), and 140 (3 %) experienced a fracture. Half of Métis citizens, compared to less than 10 % of the general population of Ontario, resided in northern regions. We identified significantly lower sex-specific and age-standardized rates of BMD testing among Métis compared to the general population, yet found little difference in fracture rates (both sexes) or pharmacotherapy (women only). Differences in BMD testing disappeared after adjusting for region of residence among women yet remained significant among men.

CONCLUSIONS

Despite finding significantly lower rates of osteoporosis management among men, Métis men and women were found to have similar age-standardized fracture rates to the general population.

Patterns of use for brand-name versus generic oral bisphosphonate drugs in Ontario over a 13-year period: a descriptive study

BACKGROUND

Bisphosphonates are the first-line therapy for the treatment of osteoporosis. In the province of Ontario, the Ontario Drug Benefit Program funds medications for patients aged 65 years and older. The Ontario Drug Benefit Program has a generic substitution policy that requires lower-cost generic drugs to be dispensed when they are available. However, there is controversy surrounding the efficacy and tolerability of generic bisphosphonates. The objective of this study was to describe patterns in the use of brand-name versus generic formulations when dispensing oral bisphosphonate over a 13-year period.

METHODS

We identified all osteoporotic preparations for alendronate and risedronate that were dispensed through the Ontario Drug Benefit Program from 2001 to 2014. We stratified our sample into community-dwelling residents and residents in long-term care facilities. The number of prescriptions dispensed per month were plotted to illustrate trends over time.

RESULTS

We found a rapid switch from brand-name to generic bisphosphonate equivalents immediately after the generic became available on the Ontario Drug Benefit formulary, with generics accounting for > 88% of dispensed drug within 2 months. We also observed a reduction in the number of generic drugs dispensed each time a new brand-name alternative (e.g., monthly risedronate, weekly alendronate plus vitamin D) was introduced to the formulary. The dispensing trends were similar in the community and long-term care settings.

INTERPRETATION

The Ontario Drug Benefit Program generic substitution policy resulted in rapid uptake of generic oral bisphosphonates among seniors in Ontario. However, there was a switch away from generic medications to new brand-name alternatives whenever they were introduced to the formulary. Therefore, some patients continued to use brand-name bisphosphonate despite the availability of generic options.

Study design considerations for a large simple trial of bisphosphonates

PURPOSE OF REVIEW

To evaluate design considerations for an osteoporosis large simple trial (LST).

RECENT FINDINGS

There is a growing need for more comparative effectiveness studies in osteoporosis. However, the design of such studies is challenged by issues surrounding study design, choosing comparator therapies, participant and outcome selection, data acquisition and data analysis.

SUMMARY

LSTs are real-world studies that can have high levels of generalizability, if designed properly. We propose novel approaches to LSTs focusing on some of the challenges associated with comparative effectiveness research in osteoporosis. In this review, we discuss these considerations in the context of bisphosphonate active comparator initiation and discontinuation trials, while presenting advantages and disadvantages of the various design aspects for such studies.

A 12-year ecological study of hip fracture rates among older Taiwanese adults

Hip fracture rates in Taiwan are among the highest in the world. The aim of this study was to describe the trends of hip fracture hospitalizations among Taiwanese elderly (aged ≥ 65 years) and the trends of antiosteoporosis medication expenditure from 1999 to 2010. We conducted an ecological study using inpatient health care-utilization data from the Department of Health, and medication expenditure data from the IMS Health, Taiwan. The International Classification of Disease, Clinical Modification, 9th version, code 820 was used to identify hip fracture hospitalizations. Medications included alendronate, calcitonin, ibandronate, raloxifene, strontium ranelate, teriparatide, and zoledronic acid. Year 2010 was assigned as the reference point for age-standardized rates, currency exchange (to the US dollar), and discount rates. Over the 12-year study period, age-standardized hip fracture hospitalizations decreased by 2.7 % annually (p for trend < 0.001) for Taiwanese elders. The decline was more obvious among those aged ≥75 years (6.1 %). However, the number of hip fracture hospitalizations increased from 14,342 to 18,023. Total hospitalization costs increased by US$0.6 ± 0.2 million annually (p for trend = 0.002); however, the per capita costs decreased by US$23.0 ± 8.0 (p for trend = 0.017). The total medication expenditure increased 7.2-fold, from US$8.1 million to US$58.9 million, accounting for an increase in the overall pharmaceutical market by fivefold, from 3.4 to 15.9 ‰ (both p for trend < 0.001). From 1999 to 2010, there was a decline in hip fracture rates among elderly Taiwanese adults with a concomitant increase in antiosteoporosis medication expenditure.

Comparison of orally administered bisphosphonate drugs in reducing the risk of hip fracture in older adults: a population-based cohort study

BACKGROUND

Orally administered bisphosphonate drugs (i.e., alendronate, etidronate, risedronate) can reduce the risk of vertebral fracture. However, only alendronate and risedronate have proven efficacy in reducing the risk of hip fracture. We sought to examine the comparative effectiveness of orally administered bisphosphonate drugs in reducing hip fractures among older adults.

METHODS

We identified new users of orally administered bisphosphonate drugs in British Columbia and Ontario between 2001 and 2008. We used province- and sex-specific propensity score-matching strategies to maximize comparability between exposure groups. We used Cox proportional hazards models to compare time-to-hip fracture within 1 year of treatment between exposures by sex in each province. Our secondary analyses considered hip fracture rates within 2 and 3 years' follow-up. We used alendronate as the reference for all comparisons and pooled provincial estimates using random effects variance-weighted meta-analysis.

RESULTS

We identified 321 755 patients who were eligible for inclusion in the study. We found little difference in fracture rates between men (pooled hazard ratio [HR] 0.94, 95% confidence interval [CI] 0.74-1.14) or women (pooled HR 1.15, 95% CI 0.73-1.56) taking risedronate and those taking alendronate. We similarly identified little difference in fracture rates between women taking etidronate and those taking alendronate (pooled HR 1.00, 95% CI 0.82-1.18). However, we identified lower rates of hip fracture among men taking etidronate relative to alendronate (pooled HR 0.77, 95% CI 0.60-0.94). Results extended to 2 and 3 years' follow-up were similar. However, with 3 years' follow-up, rates of hip fracture were lower among women in British Columbia who had taken alendronate.

INTERPRETATION

We identified little overall difference between alendronate and risedronate in reducing the risk of hip fracture in men or women. Our finding that etidronate is associated with lower fracture risk among men is likely due to selection bias. The long-term comparative effects of orally administered bisphosphonate drugs warrant further study.

Variation in the days supply field for osteoporosis medications in Ontario

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.

Evaluating the introduction of a computerized prior-authorization system on the completeness of drug exposure data

PURPOSE

Administrative databases that only capture records for benefit-approved prescriptions may underestimate exposure because they do not capture non-benefit prescriptions. Using a natural experiment, we illustrate the impact of automating a prior-authorization policy on the completeness of drug exposure.

METHODS

Using Saskatchewan (Canada) databases, weekly counts of benefit-approved and total prescription records in 2006 for new users of antidiabetic agents were examined across four categories: thiazolidinediones (TZDs), metformin, glyburide, and insulin. On July 1, 2006, Saskatchewan's public drug plan implemented an automated, online-adjudicated, prior-authorization process for TZDs; previously, prior approval was paper based. No such policy changes occurred for other drugs. We estimated the effect of this policy change on drug exposure using interrupted time-series analyses.

RESULTS

We examined 223 552 prescription records: 19% were for TZDs, 48% for metformin, 20% for glyburide, and 13% for insulin. Prior to automation, there were, on average, 571 benefit-approved TZD records per week; however, the number of benefit-approved TZD records increased immediately after the automated process was introduced by 240 prescriptions per week (95% CI 200-280, p < 0.001). The average proportion of TZD benefit-approved records was 73% before and increased to 93% immediately following policy change (20% absolute change, 95% CI 18.7-20.4%). No changes were observed for metformin, glyburide, or insulin (p > 0.1 for all).

CONCLUSIONS

Automating prior authorization for TZDs immediately increased the proportion of captured TZD records, suggesting in our study that one-fifth of TZD exposure was previously misclassified. If replicable, this indicates that even subtle changes in reimbursement policy may affect the validity of drug exposure data.

Adherence with medications used to treat osteoporosis: behavioral insights

Non-persistence (never starting or stopping medication prematurely) and non-compliance (taking medication inappropriately) with fracture prevention medication among those at high risk of fracture remain significant barriers to optimal reduction of osteoporotic fractures. Current research suggest that for patients to persist and comply with prescriptions for fracture prevention medication, they need to believe that they are at significant risk of fracture, that the prescribed medication can safely reduce their risk of fracture without exposing them to long-term harm, that equally effective non-medicinal therapies are not available, and that they can successfully execute medication use in the context of their daily task demands. Further research is needed to understand; a) the mental models of osteoporosis, fractures, and medications used to treat osteoporosis that patients employ when making decisions as to whether or not to take fracture prevention medication; and b) how patients arbitrage information from various sources (health care providers, family, friends, and other sources) to formulate their beliefs about osteoporosis and medications used to treat it.