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Allopurinol

Brand names: Zyloprim, Aloprim

Allopurinol lowers uric acid in the blood to prevent gout attacks and some kidney stones.

Brand namesZyloprim, Aloprim
Type of medicineUric acid–lowering medicine
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It doesn't treat an attack already happening. Gout flares can increase for the first few months, so providers often add a flare-prevention medicine.

What it's used for

  • Preventing gout attacks
  • Preventing some kinds of kidney stones
  • Preventing high uric acid during some cancer treatments

How to take it

  • Take it after a meal to reduce stomach upset.
  • Drink plenty of fluids.
  • Keep taking it during a gout flare unless your provider says otherwise.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Rash
  • Upset stomach or diarrhea
  • Gout flares in the first months
Call 911A blistering, peeling, or widespread red rash, especially with fever
Call 911A rash with fever, sore throat, mouth sores, or swollen glands
Call your provider todayAny new rash. Stop taking it and call your provider.
Call your provider todayYellow skin or eyes, or peeing much less

Warnings

  • Severe skin reactions are more likely in people of Han Chinese, Korean, or Thai descent with a gene called HLA-B*58:01. Testing may be offered.
  • Doses are adjusted for kidney disease.

Other medicines, foods, and alcohol

  • Azathioprine and mercaptopurine levels rise to dangerous levels.
  • Amoxicillin and ampicillin make rashes more likely.
  • It can raise the effect of warfarin.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.