allopurinol (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

DOSING: The dose of allopurinol for treating gout is 200-600 mg daily depending on severity. The dose for treating high uric acid blood levels due to chemotherapy is 100-800 mg daily starting 1 or 2 days before chemotherapy. 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. Allopurinol may increase the effect of warfarin by reducing its breakdown.

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


Medically Reviewed by a Doctor on 10/8/2014


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.

Pill Finder Tool

Need help identifying pills and medications?
Use the pill identifier tool on RxList.


Back to Medications Index