It is an antibody which combines protein parts from a mouse and protein parts from a human. This antibody is directed against certain types of cells called B cells. Not all B cells are affected. Only B cells that have a marker called CD 20 are targeted. When Rituxan is given B cells with the CD 20 marker are removed from the circulation.

Rituxan is not a new drug. It has been used extensively for some time in patients with non-Hodgkins lymphoma. Rituxan was approved by the FDA in 2006 for use in RA.

Several large trials have demonstrated Rituxan's effectiveness in both clinical and x-ray outcomes, particularly in patients who previously have had inadequate response to oral disease modifying drugs (DMARDS) such as methotrexate and TNF inhibitor therapy.

Patients who are positive for rheumatoid factor (RF) appear to respond better than RF negative patients.

While CD 20 lymphocytes are almost completely removed from the system, it appears that immunoglobulins (the antibodies that are normally made by lymphocytes to fight infections and tumors) are not depleted.

This is important from the perspective of allowing a person's natural immunity to not be adversely affected.

Rituxan is given intravenously. The first dose is administered over an 8 hour period. The next dose is administered 2 weeks later over about 5-6 hours. Patients generally do not need another infusion (intravenous dose) for at least 6 months and sometimes longer.

The most common side effects of Rituxan infusion have been itching, fever, rash, hives, chills, sneezing, swelling of the face, throat irritation, cough and shortness of breath, low blood pressure, and high blood pressure all of which are more likely to occur with the first infusion of the drug.

Premedication with intravenous methylprednisolone (Solumedrol), acetaminophen, and diphenhydramine (Benadryl) can substantially reduce the incidence of infusion reactions.

In one of the major clinical trials, the REFLEX study, the rate of serious infections was 5.2 per 100 patient-years with Rituxan compared to 3.7 per 100 patient-years with placebo.

While the risk of infection with Rituxan is low, there remains a concern because of reports of serious reactivation of chronic viral infections after Rituxan therapy. Patients with chronic hepatitis B and other viral infections should not receive Rituxan unless absolutely necessary.

Also, the FDA recently issued a public health advisory alert for Rituxan based on 2 rare case reports of patients with systemic lupus erythematosus in whom progressive multifocal leukoencephalopathy, a very rare but inevitably fatal central nervous system disorder, developed after receiving the drug. No cases of progressive multifocal leukoencephalopathy have been reported in patients with RA who were treated with Rituxan.

So far, the effectiveness and safety profile of Rituxan are encouraging. Further follow-up and more clinical studies are still needed.