OBJECTIVES: Many commercial health care plans and state Medicaid programs commonly provide coverage for bariatric surgery for patients with BMI ≥40 or BMI 35–39.9 with ≥1 obesity-related comorbidity. Coverage for anti-obesity medications, on the other hand, is less common, though some patients may benefit from anti-obesity medications and avoid bariatric surgery. This study modeled the pharmacy and medical cost implications of treating patients with lorcaserin, an FDA-approved anti-obesity medication, prior to bariatric surgery, in the California Medicaid (MediCal) population. METHODS:  The model assumed that severely obese patients (BMI ≥40) whose weight was reduced to <35 following lorcaserin treatment would avoid bariatric surgery. Model inputs included the size of the adult (age 21-64) MediCal population (6.67 million), national rate of bariatric surgery (.001%), and average cost of bariatric surgery in California ($21K). Lorcaserin treatment and outcome variables were based on results from three Phase III clinical trials (BLOSSOM, BLOOM, BLOOM-DM) evaluating the efficacy and safety of lorcaserin for weight loss. Medication specific inputs included proportion of patients responding to lorcaserin treatment (achieving ≥5% weight loss from baseline at week 12), expected weight loss, and medication acquisition costs ($145/month). The model generated cost estimates over a 2-year timeline from the payer perspective. RESULTS:  The number of patients predicted to undergo bariatric surgery was 6,140. Of these, 2,609 (42.5%) would respond to lorcaserin treatment with 459 (17.6%) obtaining a BMI<35 at one year. Medication costs for those using lorcaserin totaled $6.23 million. Bariatric surgery costs totaled $119.29 million. Predicted cost savings for patients who would avoid bariatric surgery were estimated at $2.82 million. CONCLUSIONS: For MediCal, using lorcaserin to treat obesity prior to bariatric surgery may lead to significant cost saving over a 2-year horizon. Real-world, long-term evidence is needed, however, to further evaluate of the role of lorcaserin for weight management in patients considering bariatric surgery.