OBJECTIVES: Evaluate factors and reasons associated with switching from initial biologic disease-modifying anti-rheumatic drugs (bDMARDs) in Kaiser Permanente Southern California (KPSC) RA patients; to evaluate RA related healthcare resource utilization (HCRU) and cost associated with bDMARD switching.   METHODS: A retrospective database study from time period 01/01/2007 to 12/31/2012 was used to identify KPSC patient’s ≥ 18 years of age and with a diagnosis of RA (ICD-9 714.xx). The index date was defined as the first bDMARD prescription with no prior history of bDMARD use 12 months pre-index date. Patients were followed up for 12 months post-index and were categorized into a switch group and a non-switch group during follow up. A multivariate regression analysis was conducted to evaluate factors associated with bDMARD switching. Chart notes were reviewed 30 days prior and 30 days post bDMARD switch to identify reasons for switching. RA related HCRU and costs were calculated for 12 months pre/post-index for both groups. RESULTS: CONCLUSIONS: This is a unique study that used robust data from an integrated healthcare system to evaluate reasons associated with bDMARD switching in this RA population. Reasons associated with bDMARD switching included medication adverse events, and lack/loss of efficacy; bDMARD switchers had significantly higher RA related costs.