Dormuth CR, Fisher A, Hudson M, et al. - There was no clear evidence that patients who received concomitant conventional synthetic DMARDs (csCMARD) therapy were less likely to discontinue, switch or increase their dose of bDMARD in this large study of rheumatoid arthritis (RA) patients using biologic disease-modifying antirheumatic drugs (bDMARD) in Canada and the United States.

• In this study, 20,221 new users of bDMARDs were included: adalimumab (7,609), etanercept (9,809), abatacept (1024), infliximab (1,779).

• It was shown that concomitant use of csDMARD therapy was not significantly correlated with reduced discontinuation of bDMARD treatment (hazard ratio 0.90, 95% intrinsic confidence interval 0.79 to 1.02) or reduced switching of bDMARDs (hazard ratio 0.95, 95% intrinsic confidence interval 0.80 to 1.11), but was correlated with a small increase in bDMARD dose in comparison with the mean dose over the first three months of treatment (mean percentage change in dose +0.56% mg/day, 95% intrinsic confidence interval +0.14% to +0.97%).