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.