Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
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
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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