Methotrexate polyglutamation in relation to infliximab pharmacokinetics in rheumatoid arthritis

Objective The combination of methotrexate (MTX) with infliximab can modify infliximab pharmacokinetics and lower the incidence of antibodies against infliximab (ATIs). We hypothesised that the pharmacokinetic interaction between MTX and infliximab is related to activation of MTX to immunosuppressive MTX polyglutamates (MTXPGs). Methods Adult patients with rheumatoid arthritis receiving weekly MTX with infliximab for more than 3 months were...