Deferasirox Adherence and Persistence Among Texas Medicaid Patients Taking Dispersible Tablets and Film-Coated Tablets

Background: Chronic iron overload is a significant complication associated with long-term blood transfusions required to treat patients with sickle cell disease, thalassemia, myelodysplastic syndromes, and other blood disorders. Without iron chelation therapy (ICT), which binds to and removes excess plasma iron, patients would experience iron accumulation in the body, leading to liver, heart, or other organ failure. Despite the seriousness of these complications, low adherence to ICT has been reported. Deferasirox (DFX) is a once-daily oral ICT with documented better adherence compared to parenteral deferoxamine. Before March 2015, DFX was available only as a dispersible tablet (DT) that must be mixed with liquid; however, in March 2015 the FDA approved a film-coated tablet (FCT) version of DFX. Improved adherence with DFX-FCT has been reported, but studies conducted in Medicaid populations are limited. This study investigated medication adherence and persistence between Texas Medicaid patients taking DFX-FCT and DFX-DT, and among patients who switched from DFX-DT to DFX-FCT.

Objectives: (1) To compare medication adherence and persistence between Texas Medicaid patients taking DFX-DT and DFX-FCT; and (2) to evaluate adherence and persistence in patients who switched from DFX-DT to DFX-FCT.

Methods: A retrospective analysis was conducted using 2014-2016 Texas Medicaid prescription claims data. For patients taking either DFX-DT or DFX-FCT, the index date was the date of the first DFX-DT or DFX-FCT claim between 4/1/2015 and 12/31/2015, and patients were followed for 12 months. For patients who switched from DFX-DT to DFX-FCT, the switch date was the date of the first DFX-FCT claim between 4/1/2015 and 12/31/2015. The study period was 12 months before and 12 months after the switch date. Included patients were 2-63 years of age at index/switch, and were continuously enrolled in Texas Medicaid.

Adherence was measured using the medication possession ratio (MPR) and proportion of days covered (PDC). Persistence was defined as continued access to medication without a gap of >60 days. Mann-Whitney U/Wilcoxon Signed Rank and Chi-square/McNemar tests were used for continuous and categorical variables, respectively.

Results: A total of 57 and 165 Texas Medicaid patients who met the study criteria were taking DFX-DT and DFX-FCT, respectively. MPR was not significantly different between patient groups; however, PDC was significantly greater for DFX-FCT patients (median = 0.66; mean +/- SD = 0.61 +/- 0.25) compared to DFX-DT patients (median = 0.49; mean +/- SD = 0.49 +/- 0.25; p=0.003). Nearly 30% of DFX-FCT patients were adherent (PDC >= 0.8), while 15.8% of DFX-DT patients were adherent (p=0.039). DFX-FCT patients had greater persistence over DFX-DT patients (p=0.021). Accordingly, a significantly greater proportion of DFX-FCT patients were persistent with their ICT compared to DFX-DT patients (47.3% vs. 28.1%; p=0.011).

For 121 eligible patients who switched from DFX-DT to DFX-FCT, MPR was not significantly different between pre- and post-switch periods. However, median (mean +/- SD) PDC increased from 0.58 (0.55 +/- 0.24) when patients were taking DFX-DT to 0.66 (0.66 +/- 0.23) when they switched to DFX-FCT (p<0.001), and persistence significantly increased from 227.6 days to 263.3 days (p=0.008). When patients were taking DFX-DT during the pre-switch period, 24.0% and 35.5% were considered adherent and persistent, respectively; these proportions increased to 34.7% and 54.5%, respectively, when patients switched to DFX-FCT.

Conclusions: In the Texas Medicaid population taking DFX, medication adherence and persistence is better with DFX-FCT compared to DFX-DT. To optimize patient health outcomes and use of resources, health care providers and decision-makers should be aware of adherence and persistence rates associated with ICT, and actively monitor and encourage ICT adherence among patients.