rituximab, Rituxan (cont.)

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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 and become less frequent 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 (thrombocytopenia) may occur rarely with rituximab therapy. Rituximab suppresses the immune system. Therefore, serious fungal, bacterial, and new or reactivated viral infections (for example, hepatitis B or C, shingles) can occur during or after treatment with rituximab. Generally, rituximab is avoided in the presence of active, significant infections. Rituximab also causes severe skin reactions within 1 to 13 weeks after treatment is started. Rituximab therapy is not recommended if there is an allergy to mice or rats since rituximab is made in mice or rats and may contain minute amounts of rat or mice proteins that can lead to severe allergic reactions.

Reference: FDA Prescribing Information

Last Editorial Review: 4/27/2012

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