Allopurinol
Say it: al-oh-PURE-ih-nol · Brand names: Zyloprim, Aloprim
Allopurinol is a medicine that lowers uric acid in the blood.
What it is
When cancer cells die quickly during treatment, they release a waste product called uric acid. Too much uric acid can harm the kidneys. Allopurinol blocks an enzyme the body uses to make uric acid, so less of it builds up.
Often used for
- preventing high uric acid when cancer treatment kills many cells quickly (tumor lysis)
- gout
- some kinds of kidney stones that keep coming back
How you get it
It is usually a pill taken by mouth once or more a day. A form given in a vein is used for people who cannot take pills. With cancer treatment it is often started a day or more before treatment. Your schedule may be different.
Common side effects and what helps
- Rash. Call your team at the first sign of any rash.
- Upset stomach or diarrhea. Taking it after a meal can help.
- Feeling sleepy. Do not drive until you know how it affects you.
- Gout flares when you first start, if you have gout. Tell your team.
- Changes in liver blood tests. Your team will check them.
Call your care team right away if you have
- Any new skin rash, especially with fever, blisters, peeling, or sores in the mouth or eyes
- Fever with swollen glands or swelling of the face
- Yellow skin or eyes, dark urine, or pain in the upper right belly
- Peeing much less than usual, or blood in your urine
- Pain in your side or back that could be a kidney stone
Before you start, tell your team
- If you have ever had a rash or reaction to allopurinol
- If you take azathioprine or mercaptopurine. Doses of these must change.
- If you have kidney or liver problems
- If you are of Han Chinese, Korean, or Thai descent. Your team may test for a gene that raises the risk of severe rash.
- If you are pregnant, may become pregnant, or are breastfeeding
Good to know
- Allopurinol can cause rare but very serious skin reactions. Stop and call your team at the first sign of rash.
- Drink plenty of fluids each day, unless your team tells you otherwise. This helps protect your kidneys.
- You will have blood tests to check your uric acid, kidneys, and liver.
- It interacts with some cancer and transplant medicines, so tell your team about all medicines.
At home
- Take it after a meal with a full glass of water.
- Drink plenty of fluids each day as your team tells you.
- If you miss a dose, ask your team what to do.
- Store at room temperature, away from children.
Questions to ask
- How long will I need this medicine?
- How much fluid should I drink each day?
- What should I do if I get a rash?
Side effect guides
Sources
Quick answers
- What is Allopurinol?
- Allopurinol is a medicine that lowers uric acid in the blood. Brand names: Zyloprim, Aloprim.
- What is Allopurinol used for?
- preventing high uric acid when cancer treatment kills many cells quickly (tumor lysis); gout; some kinds of kidney stones that keep coming back.
- How is Allopurinol given?
- It is usually a pill taken by mouth once or more a day. A form given in a vein is used for people who cannot take pills. With cancer treatment it is often started a day or more before treatment. Your schedule may be different.
- What are the common side effects of Allopurinol?
- Rash. Upset stomach or diarrhea. Feeling sleepy. Gout flares when you first start, if you have gout. Changes in liver blood tests.
- When should I call my care team while taking Allopurinol?
- Any new skin rash, especially with fever, blisters, peeling, or sores in the mouth or eyes; Fever with swollen glands or swelling of the face; Yellow skin or eyes, dark urine, or pain in the upper right belly; Peeing much less than usual, or blood in your urine; Pain in your side or back that could be a kidney stone.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.