OBJECTIVES: This study describes concomitant asthma medication use in patients treated with omalizumab (Xolair®), a monoclonal antibody indicated for moderate to severe persistent allergic asthma. METHODS: An analysis of health insurance claims from three large databases was conducted: MarketScan (1996-2009), Medicaid (1997-2009), and Wellpoint (2002-2010). Patients ≥12 years old newly initiated on omalizumab with 12 months of continuous insurance coverage prior to the first omalizumab dispensing (baseline period) and ≥2 asthma claims were included. Concomitant asthma medication use was summarized in eight medication classes: ICS, LABA, leukotriene modifiers, mast cell stabilizers, anticholinergics, SABA, methylxanthines, and oral corticosteroids, according to the 2007 National Asthma Education and Prevention Program guidelines for managing asthma. RESULTS: A total 6,038 patients were identified (Medicaid: 731; MarketScan: 3,521; Wellpoint: 1,786). Mean age (SD) was 38.8 (12.6), 44.6 (14.0), and 47.3 (15.6), and males represented 31%, 36%, and 39% in Medicaid, MarketScan, and Wellpoint, respectively. A high proportion of new omalizumab users have had an asthma-related ER visit (Medicaid: 34%; MarketScan: 17%; Wellpoint: 16%) or hospitalization (Medicaid: 36%; MarketScan: 14%; Wellpoint: 21%) prior to initiating omalizumab. The majority of patients (Medicaid: 96%; MarketScan: 89%; Wellpoint: 86%) received three concomitant asthma medication classes or more during the baseline period. Concomitant ICS use was observed in 95%, 89%, and 86% of Medicaid, MarketScan, and Wellpoint patients, respectively. Only 1% of omalizumab users in Medicaid and 3% in MarketScan and Wellpoint received no other asthma medication prior to initiating omalizumab. CONCLUSIONS: Based on this large observational study using health insurance claims from three databases, a minority (1-3%) of omalizumab users receive monotherapy treatment for asthma.