OBJECTIVES: Despite evidence of medication adherence benefits, many patients do not take their medications as prescribed. The objective of this study was to understand asthma medication treatment patterns among asthma patients in the US by initial asthma treatment medication. METHODS: A retrospective database analysis was conducted using Marketscan Commercial and Medicare Supplement Data. Patients were identified between 1/1/2005 through 3/31/2011 based on asthma related hospitalization, emergency room visit or at least 2 office visits at different dates within 1 year. Asthma drug utilization patterns were analyzed among patients aged 12 years or older who were initiated on an asthma medication (without asthma maintenance therapy in the past 12 months) and had at least 24 months traceable insurance coverage information since their initiation of the medication. RESULTS: Among the selected patients (n=88,567) being followed up for 24 months, approximately 30% of patients switched treatments at least once regardless of their initial asthma treatment. The three most common medications were montelukast sodium (>90% Singulair), fluticasone propionate and salmeterol (Advair) 250/50mcg and 100/50mcg.  One prevalent prescription change was to step down the steroid component.  Patients initiating asthma treatment on combination therapy (i.e. Singulair and inhaled corticosteroids) is low (between 0.3% - 1.8%) and switch patterns show that over 50% of patients switch to Singulair monotherapy.  Regardless of their initial treatment and medication switches, on average, asthma patients initiate their treatment with 2-3 months days supply; have a gap of over 6 months (~200days) and switch to another treatment. CONCLUSIONS: Our results show the high frequency of asthma medication patterns changes.  Despite the availability of prescription of asthma medications, there appears to be an unmet need and further research is necessary.