PGP and rheumatoid arthritis: In contrast, Suzuki et al. [65] using the calcineurin inhibitor tacrolimus [66,67] (that works also as inhibitor of P-gp function) in 113 RA patients refractory to MTX or other DMARDs showed that 22 patients achieved good clinical responses correlated with a reduction of P-gp expression/function on peripheral lymphocytes.