Zyloprim (allopurinol) is a medication that helps prevent attacks of gout.

Zyloprim reduces the body’s production of uric acid by inhibiting an enzyme called xanthine oxidase. This enzyme is involved in the chemical process that produces uric acid in the body. Buildups of excess uric acid can lead to gout and kidney stones.

Zyloprim belongs to a class of medications called xanthine oxidase inhibitors.

Taking Zyloprim

Zyloprim is available in 100 and 300 mg oral tablets. The usual dose for Zyloprim is between 50 to 800 mg every day, depending on a doctor’s prescription.

It takes time for this medicine to work, and patients may have flares of gout when they start. It is important for people starting Zyloprim to be patient and continue taking the medication as prescribed by their doctor.

If gout flares while taking Zyloprim, patients should see their doctor so that the flare can be treated with a different medicine.

Important Tests and Risks

Occasional Blood Tests

Patients taking Zyloprim should have their blood tested occasionally, as advised by their doctor. It is important to keep track of the gout, and make sure blood counts, liver, and kidneys are ok.

Risk of Drug Interaction

Patients taking Zyloprim should not take azathioprine as the medications may interact.

Patients should make sure their doctor and pharmacist knows all of the medications and any supplements that they are taking.

Alcohol Consumption

Drinking alcohol is known to cause flares of gout. Patients taking Zyloprim are advised to avoid alcohol completely.


How Zyloprim Works

Zyloprim (allopurinol) works by inhibiting an enzyme called Xanthine oxidase. Xanthine Oxidase is a crucial part of a chemical reaction that produces uric acid in the body. By inhibiting this enzyme, Zyloprim’s effect on the body is that it starts producing less uric acid.

Gout, the most common type of inflammatory arthritis, occurs when excess uric acid in the body builds up and starts to form into crystals in the joints, tendons, and surrounding tissues. The crystals can trigger a response by the immune system, and its attack results in the painful symptoms seen in a flare of gout.

Zyloprim helps prevent flares (attacks) of gout by reducing the amount of uric acid in the body. The accumulation of crystals is reduced, and in turn, the body’s immune response is reduced. A person’s gout will usually become less severe and really should disappear over time as they continue to take this medication.


Side Effects

When Zyloprim is first started, it can increase gout flares. It is important for patients to keep taking this medicine because in time it will help prevent and eventually stop flares. New flares that happen after starting Zyloprim can be treated with a different medicine.

Patients taking Zyloprim should have their blood tested occasionally so their doctor can make sure that it isn’t irritating their blood counts, liver, or kidneys.

Other possible side-effects of Zyloprim include:

  • Diarrhea and Nausea – Zyloprim can cause diarrhea, abdominal pain, nausea, and vomiting.
  • Skin rash – Zyloprim very rarely causes severe skin rashes. Patients who develop a skin rash should stop taking Zyloprim immediately and tell their doctor.
  • Allergic reaction – Zyloprim can sometimes cause an allergic reaction. Symptoms include fever, chills, nausea, vomiting, joint pain, and skin rash. This is rare. Patients who have an allergic reaction should stop taking Zyloprim immediately and tell their doctor
  • Drug interactions – Zyloprim (allopurinol) should not be taken with azathioprine

Patients should talk to their doctor if they are concerned about any side effects.

Zyloprim can safely be stopped without needing to be weaned off. Patients should tell their doctor if they stop taking this medicine.

Zyloprim has not been studied for safety in pregnancy. Patients should let their doctor know if they are planning to get pregnant or if they are breastfeeding.

Who Should NOT Take Zyloprim

Patients who should NOT be taking Zyloprim include:

  • Patients who have had a previous reaction to Zyloprim
  • Patients taking azathioprine, or other medications with possible interactions

Patients who become pregnant while taking Zyloprim should notify their doctor immediately.

When to Call a Doctor

Patients should call their doctor if they feel sick and want to stop, or they you are concerned about any side effects.

Other reasons to call a doctor while taking Zyloprim include:

  • Rash
  • Flare of gout
  • Allergic reaction
  • Becoming pregnant or planning pregnancy


Watch Canadian rheumatologist Dr. Andy Thompson introduce Zyloprim in this short video: