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rituximab, Rituxan

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GENERIC NAME: rituximab

BRAND NAME: Rituxan

DRUG CLASS AND MECHANISM: Rituximab is an intravenous drug that is used to treat rheumatoid arthritis and B-cell non-Hodgkin's lymphoma. It belongs to a class of drugs called monoclonal antibodies. Other monoclonal antibodies include trastuzumab (Herceptin) and gemtuzumab ozogamicin (Mylotarg).

Tumor cells (like most normal cells) have receptors on their surfaces. Molecules on the outside of the cell can attach to these receptors. When they do, they can cause changes to occur within the cells. One receptor, present in more than 90% of B-cell non-Hodgkin's lymphomas, is called CD20. Molecules that attach to CD20 can affect the growth and development of the tumor cells and, sometimes, the production of new tumor cells. Rituximab is a man-made antibody that was developed using cloning and recombinant DNA technology from human and murine (mice or rat) genes. Rituximab is thought to attach to the CD20 receptor and cause the tumor cells to disintegrate (lyse). In some non-Hodgkin's lymphomas, it also prevents the production of more tumor cells. Rituximab was approved by the FDA in 1997.

In the treatment of rheumatoid arthritis, rituximab is used when other biologic medications (TNF-blockers, such as infliximab, etanercept, or adalimumab) have failed to be effective. The effectiveness of rituximab is a result of itstemporarily depleting the number of the B-cells, cells of the immune systemwhich are important in promoting inflammation in rheumatoid arthritis.

GENERIC AVAILABLE: no

PRESCRIPTION: yes

PREPARATIONS: Rituximab is available as a liquid in single-use vials containing 100mg or 500mg of drug. It must be mixed with another liquid before intravenous injection. Rituximab is free of preservatives.

STORAGE: Rituximab, once mixed, can be stored at 2-8°C (36-36°F) for up to 24 hours and at room temperature for up to 12 hours. The drug should be protected from sunlight.

PRESCRIBED FOR: Rituximab is used to treat non-Hodgkin's B-cell lymphomas that have CD20 receptors on their surface. It is used when the lymphomas recur following other types of therapy or are unresponsive to other types of therapy.

Rituximab also is effective for treating rheumatoid arthritis and is used in patients that have failed other biologic medications, such as infliximab, etanercept, or adalimumab.

DOSING: Rituximab usually is administered once weekly for four weeks at a dose of 375 mg per meter-squared.

DRUG INTERACTIONS: There have been no studies of drug interactions with rituximab.

PREGNANCY: There are not enough studies to draw conclusions about the safety of rituximab in pregnant women. Contraceptive methods are recommended if rituximab is used in women of childbearing age and for up to 12 months after stopping therapy.

NURSING MOTHERS: Nursing mothers should avoid rituximab therapy and not begin nursing until rituximab is no longer present in the blood. Since rituximab is an antibody that can be secreted into breast milk and absorbed by the infant, it has the potential for harming nursing infants.

SIDE EFFECTS: The most common side effect of rituximab is a constellation of symptoms (fever, rigors and chills) that occur during administration of the first dose of drug. More than 80% of patients experience these side effects, and it is severe in 4-7 out of every 10,000 patients. The side effects appear only 40% of the time with the second dose of drug and decreases even less frequently with the last two doses. Other common side effects related to rituximab are nausea, hives, fatigue, headache, itching, difficulty breathing due to bronchospasm, a sensation of swelling of the tongue or throat, runny nose, vomiting, decreased blood pressure, flushing, and pain at the site of the tumor.

After rituximab is administered, large numbers of tumor cells are immediately destroyed (lysed) and eliminated from the body. In 4-5 out of every 10,000 patients the products from the dead cells cannot be eliminated quickly enough and a syndrome called tumor lysis syndrome occurs. This is characterized by a rapid decline in kidney function and a sudden accumulation or decrease in minerals such as potassium, calcium and phosphate to dangerous levels. Tumor lysis syndrome occurs when the size of the tumor or the number of tumor cells circulating in the blood is large, usually within 12-24 hours after the first dose of rituximab.

Irregular heart rhythms and infection are two other rarely-occurring side effects that may be severe. The irregular heart rhythm usually begins soon after the administration of the drug, while infection may develop from 30 days to 11 months after the end of therapy.

Severe decreases in red or white blood cells and platelets may occur rarely with rituximab therapy.Generally, rituximab is avoided in the presence of active significant infections.

Rituximab therapy is not recommended if there is an allergy to mice or rats since rituximab is made in miceor rats and may contain minute amounts of rat or mice proteins that canlead to severe allergic reactions.

Reference: FDA Prescribing Information

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