OBJECTIVES: This study evaluated the impact of omalizumab on emergency-department (ED) visits, hospitalizations and corticosteroid use among uncontrolled asthma patients using high-dose inhaled corticosteroids (ICS) prior to initiating omalizumab. METHODS: Health insurance claims from the MarketScan database (2002Q1-2009Q1) were analyzed. Patients with ≥12 months of continuous insurance coverage prior to and after the first omalizumab dispensing, ≥8 weeks of high-dose ICS use, ≥8 weeks of long-acting beta2-agonist (LABA) use, and uncontrolled asthma at baseline were included. A retrospective analysis was conducted to quantify the impact of omalizumab on resource use by comparing ED visits, hospitalizations, and corticosteroid use one year before and after omalizumab initiation. A one-year period was chosen to cover any potential seasonality impacts. RESULTS: A total of 644 patients (mean age: 49.9; female: 59.2%) formed the study population. Omalizumab was associated with a 48.6% reduction in the proportion of patients with ≥1 asthma-related ED visits (pre vs. post-omalizumab period: 21.4% vs. 11.0%, P<0.001) and 40.8% reduction in asthma-related hospitalizations (25.0% vs. 14.8%, respectively, P<0.001). Compared to the pre-omalizumab period, the use of ICS decreased significantly after omalizumab initiation (7.8 vs. 6.5 dispensings, P<0.001; 41.9% of patients had a reduction in ICS use). A similar reduction in oral corticosteroid use was observed (5.0 vs. 3.6 dispensings, P<.001; 53.3% of patients had a reduction in oral corticosteroid use). CONCLUSIONS: The results of the current study showed that omalizumab treatment initiation was associated with statistically significant reductions in ED visits, hospitalizations and corticosteroid use.