Medication utilization, adherence and use of relief agents among Texas medicaid patients with persistent asthma

Asthma is a prevalent chronic disease with high health care utilization and excessive costs. Adherence to asthma long-term controller medications is one of the key drivers to improve asthma management. The purpose of this study was to investigate how patient characteristics and medication regimens, including adherence, impact asthma-related outcomes, which was represented by the use of quick-relief medications: oral corticosteroids (OCSs) and short-acting [beta]2-agonists (SABAs). Texas Medicaid prescription claims from July 1, 2008 to August 31, 2010 were retrospectively analyzed. Patients aged 5-63 years with a primary diagnosis of asthma (ICD-9 code 493) and four or more prescription claims for any asthma medication in one year (persistent asthma) were included. The primary outcomes were adherence to asthma long-term controller medications estimated by Proportion of Days Covered (PDC) and asthma control defined by the number of OCS and SABA claims. A total of 32,172 patients were included in the study. The majority of the patients were on monotherapy (58.9%), with leukotriene receptor antagonists (LTRAs) being most commonly prescribed (65.6%). Among patients on combination therapy (41.1%), fixed dose combinations of inhaled corticosteroids (ICSs) plus long-acting β-agonists (LABAs) were most commonly prescribed (51.9%). Mean (±SD) adherence to controller therapy was 32.2% (±19.7). Patients on LTRAs were 7.7% more adherent compared to patients on ICS therapy, and patients on fixed dose combination therapy were 4.5% more adherent compared to patients on concurrent therapy, while controlling for covariates (age, gender, race, number of non-study medications) (p<0.0001). The likelihood of having 6 or more claims for SABA in one year was significantly higher for adherent (PDC≥50%) patients (p<0.0001). However, the likelihood of OCS use was significantly higher for nonadherent (PDC<50%) patients compared to those who were adherent (p<0.0001). In conclusion, adherence to long-term controller medications was low among patients with asthma. Healthcare providers should emphasize adherence to controller therapy among patients with asthma. Being adherent is critical in prevention of asthma exacerbations requiring OCS use. As frequent SABA use signals poor asthma control, healthcare providers and patients (both adherent and nonadherent) should be educated/re-educated about SABA inhaler use.