allopurinol, Zyloprim, Aloprim

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GENERIC NAME: allopurinol

BRAND NAME: Zyloprim, Aloprim

DRUG CLASS AND MECHANISM: Allopurinol is used for treating gout caused by excessive levels of uric acid in the blood (hyperuricemia). Uric acid is a by product from the breakdown of certain proteins (purines) in the body. Hyperuricemia occurs when the body produces more uric acid than it can eliminate. The uric acid forms crystals in joints (gouty arthritis) and tissues, causing inflammation and pain. Elevated blood uric acid levels also can cause kidney disease and stones. Allopurinol prevents the production of uric acid by blocking the activity of the enzyme that converts purines to uric acid. Uric acid levels usually begin to fall within 2-3 days of starting treatment and return to their original levels within 7-10 days after allopurinol is stopped. It may take several months of therapy before attacks of gout are controlled. The FDA approved allopurinol prior to 1982.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets: 100, 300 mg; Powder for injection: 500 mg

STORAGE: Tablets should be stored at room temperature between 15 to 25 C (59-77 F) and in a moisture proof, light- resistant container. Powder should be stored between 20 and 25 C (68-77 F) and not refrigerated.

PRESCRIBED FOR: Allopurinol is used for treating acute attacks of gout, erosive destructive gouty joint disease, uric acid deposits in tissues (tophi), gouty kidney disease, and uric acid stones. Allopurinol also is used to prevent elevation of blood uric acid in patients undergoing chemotherapy for the treatment of certain cancers and in patients with recurrent calcium kidney stones and elevated uric acid levels.

DOSING: The dose range of allopurinol is 100-800 mg day. It should be taken with food to avoid irritation of the stomach. In order to avoid formation of kidney stones, patients should drink plenty of fluids while taking allopurinol.

DRUG INTERACTIONS: Allopurinol increases blood levels of oral mercaptopurine (Purinethol) and azathioprine (Imuran) by reducing their breakdown in the body. Therefore, the dose of mercaptopurine and azathioprine should be reduced in order to avoid toxicity. There is an increased risk of skin rash in patients taking allopurinol in combination with penicillins.

PREGNANCY: There are no adequate studies of allopurinol in pregnant women.

NURSING MOTHERS: Allopurinol is excreted in breast milk. To avoid adverse effects in the infant, nursing mothers taking allopurinol should consider not breastfeeding.

SIDE EFFECTS: Common reactions include diarrhea, nausea, rash and itching, and drowsiness. The most frequent side effect to allopurinol is skin rash. Allopurinol should be discontinued immediately at the first appearance of rash, painful urination, blood in the urine, eye irritation, or swelling of the mouth or lips, because these can be a signs of an impending severe allergic reaction that can be fatal. Allopurinol should be avoided by patients with a prior severe reaction to the drug. Allopurinol can cause a flare-up of gouty arthritis during initial therapy. Therefore, colchicine often is used simultaneously to prevent these flares.

Rarely, allopurinol can cause nerve, kidney, and bone marrow damage. Allopurinol can cause a serious allergic liver toxicity that can be fatal. Appetite loss and itching can be signs of liver toxicity. The risk of this reaction increases in patients with kidney impairment. Patients with kidney impairment should receive lower doses of allopurinol.

Reference: FDA Prescribing Information


Last Editorial Review: 3/11/2009




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