Adherence to prescribed treatment for asthma: evidence from pharmacy benefits data.

BACKGROUND: Failure to use asthma controller medications as prescribed is associated with more asthma-related adverse events. Medication utilization may vary with ease of drug administration, efficacy, and tolerability as well as other factors. We hypothesized that in usual-care clinical practice settings, there would be greater adherence to oral controller than to inhaled controller asthma medications.

METHODS: We compared adherence to newly initiated asthma controller therapy among patients initiating monotherapy with leukotriene receptor antagonists (LTRAs), inhaled corticosteroids (ICS), or inhaled long-acting beta-agonists (ILBA) from March 1998 to July 1999. We measured adherence as the sum of drug supply days between first and last fill dates divided by length of drug therapy. Analyses were stratified by the number of short-acting beta-agonists (SBA) prescriptions per year to control for disease severity.

RESULTS: Pharmacy claims data from 48,751 subjects (6 to 55 years) were analyzed (mean age 30.4 years; 56% female). Mean adherence to new start monotherapy on LTRA was 67.7%, to ICS was 33.8%, and to ILBA was 40.0%. Adherence to all three controller agents increased with increasing SBA use. The percent of patients persistent to asthma controller monotherapy at both 6 and 9 months was significantly greater among those on LTRA monotherapy than on either ICS or ILBA.

CONCLUSIONS: In clinical practice settings, patients initiating LTRA monotherapy have about twice the adherence as patients initiating ICS or ILBA monotherapy. Because adherence to treatment is a critical component of treatment response, it is important to consider this factor in the prescription of oral vs. inhaled asthma medications.