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Zyloprim Side Effects

Generic name: allopurinol

Medically reviewed by Drugs.com. Last updated on Jun 3, 2024.

Note: This document provides detailed information about Zyloprim Side Effects associated with allopurinol. Some dosage forms listed on this page may not apply specifically to the brand name Zyloprim.

Applies to allopurinol: intravenous powder for solution.

Other dosage forms:

Precautions

It is very important that your doctor check you or your child closely while you are receiving this medicine. This is to make sure that the medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Receiving this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during treatment with this medicine. If you think you have become pregnant while receiving this medicine, tell your doctor right away.

If you or your child develop a skin rash, hives, swelling of the lips or mouth, or any allergic reaction to this medicine, tell your doctor or nurse right away.

This medicine may cause serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome, and drug reaction with eosinophilia and systemic symptoms (DRESS). Check with your doctor right away if you or your child have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, fever, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, swollen glands, unusual bleeding or bruising, or unusual tiredness or weakness.

Check with your doctor right away if you or your child have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin. These could be symptoms of a serious liver problem.

Check with your doctor right away if you have bloody urine, a decrease in frequency or amount of urine, an increase in blood pressure, increased thirst, loss of appetite, lower back or side pain, nausea, swelling of the face, fingers, or lower legs, trouble breathing, unusual tiredness or weakness, vomiting, or weight gain. These could be symptoms of a serious kidney problem.

Check with your doctor right away if you or your child have chest pain, chills, cough or hoarseness, fever, lower back or side pain, painful or difficult urination, sores, ulcers, or white spots on the lips or in the mouth, swollen glands, unusual bleeding, bruising, tiredness, or weakness. These could be symptoms of bone marrow suppression.

This medicine lowers the number of some types of blood cells in your body. Because of this, you may bleed or get infections more easily. To help with these problems, avoid being near people who are sick or have infections. Wash your hands often. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Brush and floss your teeth gently. Be careful when using sharp objects, including razors and fingernail clippers.

This medicine may cause some people to become drowsy or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of Zyloprim

Along with its needed effects, allopurinol (the active ingredient contained in Zyloprim) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking allopurinol:

Less common side effects

  • agitation
  • coma
  • confusion
  • decreased urine output
  • depression
  • dizziness
  • headache
  • hostility
  • irritability
  • lethargy
  • muscle twitching
  • nausea
  • rapid weight gain
  • seizures
  • stupor
  • swelling of the face, ankles, or hands
  • unusual tiredness or weakness

Rare side effects

  • black, tarry stools
  • bladder pain
  • bleeding gums
  • blistering, peeling, loosening of the skin
  • blood in the urine or stools
  • blurred vision
  • changes in skin color
  • chest pain or tightness
  • chills
  • clay-colored stools
  • cloudy urine
  • cough or hoarseness
  • coughing up blood
  • dark urine
  • diarrhea
  • difficult, burning, or painful urination
  • difficulty with breathing or swallowing
  • difficulty with speaking
  • dilated neck veins
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • double vision
  • enlarged stomach
  • fainting
  • fast or slow heartbeat
  • feeling of warmth
  • fever
  • frequent urge to urinate
  • inability to move the arms, legs, or facial muscles
  • inability to speak
  • increased menstrual flow or vaginal bleeding
  • increased sweating
  • irregular breathing
  • irregular heartbeat
  • itching, rash
  • joint pain, stiffness, or swelling
  • lightheadedness
  • loosening of the fingernails
  • loss of appetite
  • loss of strength or energy
  • lower back or side pain
  • muscle pain or weakness
  • nosebleeds
  • numbness, tingling, pain, or weakness in the hands or feet
  • pain, tenderness, or swelling of the foot or leg
  • painful or difficult urination
  • paralysis
  • pinpoint red spots on the skin
  • prolonged bleeding from cuts
  • rapid, shallow breathing
  • red or black, tarry stools
  • red or dark brown urine
  • red skin lesions, often with a purple center
  • redness of the face, neck, arms, and occasionally, upper chest
  • slow speech
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • stomach pain
  • sweating
  • swelling of the fingers, feet, or lower legs
  • swollen glands
  • trouble breathing
  • unpleasant breath odor
  • unusual bleeding or bruising
  • unusual weak feeling
  • vomiting of blood
  • weight gain
  • yellow eyes or skin

Other side effects of Zyloprim

Some side effects of allopurinol may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common side effects

  • drowsiness
  • indigestion
  • unusual hair loss

Rare side effects

  • bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
  • body aches or pain
  • congestion
  • cracked lips
  • difficulty with moving
  • hair loss or thinning of the hair
  • hives or welts
  • muscle stiffness
  • pain, redness, swelling, tenderness, or warmth on the skin
  • runny nose
  • voice changes

For healthcare professionals

Applies to allopurinol: intravenous powder for injection, oral tablet.

General adverse events

The most common adverse reaction was skin rash, nausea, diarrhea, vomiting, renal failure or insufficiency and increase in liver function tests.[Ref]

Cardiovascular

Dermatologic

Endocrine

Gastrointestinal

Hematologic

Hepatic

Hypersensitivity

Local

Metabolic

Musculoskeletal

Nervous system

Ocular

Oncologic

Other

Psychiatric

Renal

Respiratory

See also:

References

1. (2022) "Product Information. Zyloprim (allopurinol)." Glaxo Wellcome

2. Cerner Multum, Inc. "UK Summary of Product Characteristics."

3. (2025) "Product Information. Allosig (allopurinol)." Arrow Pharma Pty Ltd, 18 March 2025

4. (2025) "Product Information. Zyloric (allopurinol)." Aspen Pharma Trading Ltd, 19 Feb 2025

5. (2022) "Product Information. Aloprim (allopurinol)." Mylan Institutional LLC, 2/2022

6. (2023) "Product Information. Zyloprim (allopurinol)." Casper Pharma LLC, 9/2023

7. (2024) "Product Information. Allopurinol (allopurinol)." Leading Pharma, LLC, 9/2024

8. Cerner Multum, Inc. "Australian Product Information."

Further information

Zyloprim side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.