Common Adverse Effects

Allopurinol is tolerated well by most patients. The most common adverse effects are hypersensitiv-ity reactions that may occur after months or years of medication. The effects usually subside within a few days after medication is discontinued. Serious reactions preclude further use of the drug.

The cutaneous reaction caused by allopurinol is predominantly a pruritic, erythematous, or maculopapular eruption, but occasionally the lesion is urticarial or purpuric. Rarely, toxic epidermal necrolysis or Stevens-Johnson syndrome occurs, which can be fatal. The risk for StevensJohnson syndrome is limited primarily to the first 2 months of treatment. Because the rash may precede severe hypersensitivity reactions, patients who develop a rash should discontinue allop-urinol. If indicated, desensitization to allopurinol can be carried out starting at 10-25 mg/day, with the drug diluted in oral suspension and doubled every 3-14 days until the desired dose is reached. This is successful in approximately half of patients. Oxypurinol is available for compassionate use in the U.S. for patients intolerant of allopurinol. The safety of oxypurinol in patients with severe allopurinol hypersensitivity is unknown; it is not recommended in this setting.

Fever, malaise, and myalgias also may occur. Such effects are noted in ~3% of patients with normal renal function and more frequently in those with renal impairment.

Transient leukopenia or leukocytosis and eosinophilia are rare reactions that may require cessation of therapy. Hepatomegaly and elevated levels of transaminases in plasma and progressive renal insufficiency also may occur.


Rasburicase (elitek) is a recombinant urate-oxidase that catalyzes the enzymatic oxidation of uric acid into the soluble and inactive metabolite allantoin. It lowers urate levels more effectively than allopurinol and is indicated for the initial management of elevated plasma uric acid levels in pedi-atric patients with leukemia, lymphoma, and solid tumor malignancies who are receiving anticancer therapy expected to result in tumor lysis and significant hyperuricemia.

Produced by a genetically modified Saccharomyces cerevisiae strain, the therapeutic efficacy may be hampered by the production of antibodies against the drug. Hemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient patients, methemoglobinemia, acute renal failure, and anaphylaxis all have been associated with the use of rasburicase. Other frequently observed adverse reactions include vomiting, fever, nausea, headache, abdominal pain, constipation, diarrhea, and mucositis. Rasburicase causes enzymatic degradation of the uric acid in blood samples, and special handling is required to prevent spuriously low values for plasma uric acid in patients receiving the drug. The recommended dose of rasburicase is 0.15 mg/kg or 0.2 mg/kg as a single daily dose for 5 days, with chemotherapy initiated 4-24 hours after infusion of the first rasburic-ase dose.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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