Imutrex 7.5 Tablet belongs to a group of medicines called antimetabolites. It may be used to treat severe rheumatoid arthritis if other treatments have already been tried and have not worked. It is not a first-line treatment. It works by reducing the body's immune system, this decreases swelling, reduces pain, stiffness, and improves function. Take it exactly as prescribed and for as long as it is prescribed to get the most benefit. Do not take more than you should. It may take several months to become fully effective.