Rasburicase
Unlike allopurinol, rasburicase is a drug that treats hyperuricemia. Administered intravenously, rasburicase converts uric acid to allantoin, which is much more soluble in urine than uric acid is. The drug works quickly (in four hours) to reduce uric acid levels and also helps control serum potassium, phosphate, calcium, and creatinine levels.
Most patients receive two days of therapy, but just one treatment is effective for some. Patients with a large tumor burden may need longer therapy (up to seven days) or twice-daily treatment. If you care for a patient taking rasburicase, pay special attention when sending lab specimens for uric acid analysis. To ensure accurate uric acid results, the blood specimen must be placed on ice after being drawn, during transport, and while in the lab waiting to be processed. Improperly obtained and maintained specimens will give abnormal false low results due to any uric acid in the tube being degraded by rasburicase at room temperature. Allopurinol must be stopped in patients who are to receive rasburicase. Never use the two drugs together because allopurinol will interfere with rasburicase activity. Make sure the patient is well hydrated before administering rasburicase. Because of the risk of a hypersensitivity reaction, make sure emergency medications (such as oxygen, epinephrine, corticosteroids, and diphenhydramine) are available before rasburicase therapy begins. Take baseline vital signs and closely monitor the patient throughout drug administration. Signs of hypersensitivity reactions include urticaria, bronchospasm, chest discomfort, dyspnea, hypoxia, and hypotension. Stop the rasburicase infusion at the first sign of a hypersensitivity reaction; assess and maintain airway, breathing, and circulation, obtain vital signs, notify the health care provider, administer treatment as ordered, and support the patient during the reaction. Headache, rash, fever, and vomiting are the most common adverse reactions associated with one dose of rasburicase. With repeated dosing, additional adverse reactions include increased liver enzymes, urticaria, pruritus, flushing, dyspnea, and chest and back pain. Hemolysis, hemoglobinuria, and methemoglobinemia have been reported. Rasburicase should never be administered to patients with a glucose-6-phosphate dehydrogenase deficiency because of the risk of severe hemolysis.
