Rasburicase is a recombinant uric acid oxidase that is used to rapidly reduce plasma uric acid levels in patients with hyperuricemia due to tumor lysis syndrome. Rasburicase converts urate to allantoin and hydrogen preroxide. Allantoin is water soluble and rapidly excreted by the kidney.
Rasburicase continues to degrade uric acid in vitro. If a blood sample is collected and held at room temperature for one hour before testing, uric acid is decreased by 20%. If a patient is receiving rasburicase, blood samples for measurement of uric acid should be collected in pre-chilled heparinized tubes and immediately placed in ice for transportation to the laboratory. Ideally, specimens should be centrifuged in a refrigerated centrifuge. Under these conditions, uric acid levels are stable up to 4 hours.