Both the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) guidelines propose the use of methotrexate (MTX) for rheumatoid arthritis (RA) treatment when there is no contraindication. Methotrexate comes under the class of drugs called antimetabolites which acts by slowing or stopping the growth of cancer cells and repressing the immune system.

MTX is a bedrock of RA therapy, although absorption saturation undermines its oral bioavailability (BA). The need for guidance on successful dose-conversion methods arise due to the differences in the relative BA of oral versus subcutaneous (SC) MTX.  The study mentioned here was performed to distinguish MTX PK profiles as a consequence of MTX administration via three distinct treatment administrations: oral, SC MTX administered via an auto-injector (MTXAI) into the abdomen (MTXAIab) and into the thigh (MTXAIth). A dose-conversion method based on the BA of MTX from oral and SC administration was initiated in this paper.

The SC administration supplemented higher exposure of MTX than the same dose given orally. The dose-proportional exposure was seen with SC MTX unlike the exposure restrictions of oral MTX.