OBJECTIVES: Tumor necrosis factor blocker (TNFb) therapy is an expensive alternative for rheumatoid arthritis (RA) sufferers when other treatments have failed. The purpose of this analysis was to compare two products, adalimumab and etanercept, in terms of adherence, persistency, and appropriateness of use. METHODS: Retrospective claims data between October 2005-September 2008 were extracted from an organization with ~30,000 individuals. Inclusion criteria were primary diagnosis of RA, new start of TNFb therapy defined as none in preceding sixmonths, and continuous enrollment at least 6 months pre- and 12 months post-TNFb initiation. A refill grace period was defined as ½ days supply for prescriptions =<30 days or 1/3 days supply for prescriptions >30days. RESULTS: A total of 334 individuals met criteria, and of those 57 received study medication; 12 were excluded for receiving both medications during the 12-month period, leaving 43 individuals for analysis (adalimumab n=24; etanercept n=19). No statistical differences (p>0.05) were found in adherence or persistency by drug, age, or gender. Mean medication possession ratio (MPR) over 12 months was 0.61 (st dev=0.35) and mean annual days supply was 228 (st dev=136). After the first month, 30% exceeded the refill grace period, and by month 6, this increased to 80%. Thirty-nine (91%) received other prescription RA medication in the 6 months prior to initiating TNFb therapy. CONCLUSIONS: While preliminary, the results from this analysis indicate that gaps in adalimumab and etanercept therapy occur early in care, thereby impacting adherence and persistence rates. While individuals in this analysis received approximately seven total months of therapy over a year, gaps between refills may impact effectiveness. Efforts to improve adherence and persistence of RA therapy are needed to maximize patient outcomes. Most patients had received alternative therapy before initiating TNFb treatment, and none received concomitant TNFb therapy, which aligns with current guidelines.