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The American Journal of Managed Care Special Issue: Pharmacy Benefits
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Direct Oral Anticoagulant Prescription Trends, Switching Patterns, and Adherence in Texas Medicaid
Shui Ling Wong, MS; Landon Z. Marshall, PharmD; and Kenneth A. Lawson, PhD
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Direct Oral Anticoagulant Prescription Trends, Switching Patterns, and Adherence in Texas Medicaid

Shui Ling Wong, MS; Landon Z. Marshall, PharmD; and Kenneth A. Lawson, PhD
Direct oral anticoagulants (DOACs) are associated with increased prescription costs. Actual practice data show a high switch rate and poor adherence among DOAC initiators that need to be addressed.

Objectives: To compare prescription trends, costs, switch patterns, and mean adherence among oral anticoagulants in the Texas Medicaid population.

Study Design: Secondary analysis of Medicaid prescription claims data.

Methods: All oral anticoagulant prescriptions for patients aged 18 to 63 years with 1 or more prescription claims for an oral anticoagulant from July 1, 2010, to December 31, 2015, were included in utilization and expenditure trend analyses. Switch patterns and adherence, measured by the proportion of days covered (PDC), were analyzed over 1 year for patients newly initiated on oral anticoagulant therapy.

Results: Over the 5.5-year study period, direct oral anticoagulant (DOAC) use increased steadily and the proportion of oral anticoagulant prescription expenditures accounted for by DOACs increased substantially. By December 2015, DOACs accounted for one-third of anticoagulant prescription claims and more than 90% of total oral anticoagulant prescription expenditures. The mean cost per prescription was 30 times higher for DOACs than warfarin. A higher proportion of patients with a DOAC as an index drug switched drugs. The overall mean ± SD PDC was 0.71 ± 0.21, with no significant differences among patients on dabigatran, rivaroxaban, and apixaban. Using a PDC cutoff point of 0.80 to indicate adherence (vs nonadherence), 42% of patients were categorized as adherent.

Conclusions: Texas Medicaid prescription data show a gradual increase in DOAC use with a rapid increase in prescription expenditures. Further exploration of the causes of higher switch rates among DOAC initiators compared with warfarin initiators and nonadherence to DOACs is needed to understand the challenges related to DOAC adoption in practice and to improve patient outcomes.

Am J Manag Care. 2018;24(Spec Issue No. 8):SP309-SP314
Takeaway Points

Direct oral anticoagulants (DOACs) are changing the practice of anticoagulation and are associated with increased prescription costs. This study examined the prescription trends, switching patterns, and adherence to DOACs in the Texas Medicaid population.
  • DOACs imposed a high cost burden on Medicaid. Specifically, in 2015, more than 90% of Texas Medicaid oral anticoagulant prescription spending was for DOACs.
  • Among new users, patients initiated on a DOAC had higher switch rates than warfarin initiators.
  • Poor adherence among patients taking DOACs should be further investigated to optimize the efficiency of DOACs.
Anticoagulants prevent the clotting process by inhibiting thrombin formation and, ultimately, fibrin formation. This reduces blood clots that may lead to venous thromboembolism, stroke, and death.1-3 Warfarin, a coumarin derivative, is the most commonly used oral anticoagulant.1,2 However, the use of warfarin has long been associated with challenges, including the need for close monitoring and frequent dosage adjustments due to the narrow therapeutic index and other factors that influence response to the medication.1,2 This conventional approach to anticoagulation is changing with the availability of direct oral anticoagulants (DOACs).4

DOACs have been approved by the FDA in recent years—dabigatran, October 2010; rivaroxaban, July 2011; apixaban, December 2012; edoxaban, January 2015; betrixaban, June 2017—with indications for risk reduction for stroke and embolism in nonvalvular atrial fibrillation (AF).5 DOACs have also been approved for prophylaxis and treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE).6-8 This new generation of anticoagulants does not require frequent laboratory monitoring or dosage adjustments. Additionally, DOACs have fewer drug interactions, food interactions, and adverse effects compared with warfarin.3,9 The promising efficacy and safety profiles of the DOACs demonstrated in clinical trials have been reflected in guideline updates, and the use of DOACs is anticipated to increase.10 Nevertheless, there are limited data on the actual adoption of, and adherence to, these agents in clinical practice, particularly regarding utilization patterns of the different agents.11,12

Previous studies that examined the use of DOACs compared with warfarin found an increase in DOAC use and a decrease in warfarin use.11,13-15 One study reported that the costs of DOACs in terms of patient out-of-pocket and insurance spending were 5 and 15 times higher compared with warfarin, respectively.11 The same study also reported that DOACs accounted for more than 90% of one private insurer’s spending on anticoagulants. On the other hand, Medicaid patients have been described as having a greater comorbidity burden and higher stroke risk, but contrastingly lower odds of receiving oral anticoagulants, compared with patients not insured by Medicaid.16

An 8-month adherence study in patients with AF conducted in 2011 found that almost 70% of Medicaid patients were adherent to dabigatran (average medication possession ratio [MPR], 0.87). However, about one-fifth of the patients switched to warfarin after initiating treatment with dabigatran.12 There are limited data about DOAC adherence, yet having actual practice evidence is important in understanding patient adherence and, subsequently, patient outcomes. Finally, no current literature has described the use of all 4 DOACs in the Medicaid population. Therefore, this study aims to contribute to the growing literature on utilization of, expenditures on, and adherence to DOACs, with a focus on the Texas Medicaid population.


To compare trends in prescription utilization, expenditures, switching patterns, and adherence among oral anticoagulants in the Texas Medicaid population.


This was a secondary analysis of prescription claims data from Texas Medicaid from July 1, 2010, to December 31, 2015. Texas Medicaid provides coverage for more than 4 million beneficiaries.17 This joint federal–state program provides low-income Texans with access to healthcare. These prescription claims data include unique patient identifiers (not actual patient identification numbers), drug name/strength, dispense date, paid amount, National Drug Code, quantity dispensed, days supplied, and patient gender and age. The first part of the study examined utilization and prescription expenditure trends of oral anticoagulants. All Medicaid prescription claims data for patients aged 18 to 63 years with at least 1 prescription claim for an oral anticoagulant (ie, dabigatran, rivaroxaban, apixaban, edoxaban, warfarin) during the study period were included in these analyses.

The second part of the study analyzed switching patterns and adherence for patients who were newly initiated on oral anticoagulant therapy between January 1, 2011, and December 31, 2014 (index period). The index date was defined as the earliest anticoagulant prescription drug claim during the index period, and patients were followed for 1 year (365 days) after the index date. Continuous Medicaid enrollment was required during the 6-month period prior to and the 12-month period following the index date, defined as the pre- and postindex periods, respectively. Only patients defined as new initiators of anticoagulant therapy were included (ie, no anticoagulant claim in the preindex timeframe). Figure 1 illustrates the study timeline.

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