How long does rituxin stay in the body?

About 6 months: Typically, after the loading doses (which are usually 2 weeks apart), the physiological effects of Rituxan (rituximab) on the body's production of certain types of white blood cells can be seen for upwards of 6 months (sometimes longer)

1/2 life 18-32 days: The 1/2 life is 18-32 days. So it usually takes 5 1/2 lives to be out of the body. However its tissue effects and removal of B lymphocytes can have much longer effects - 4 months to over a year clinically in people with Rheumatoid Arthritis.