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At a Glance
Metabolizes in just 2 hours
Easy to administer tablet for the treatment of bladder stones
Dissolves pre-existing stones


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At a Glance
Metabolizes in just 2 hours
Easy to administer tablet for the treatment of bladder stones
Dissolves pre-existing stones

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Allopurinol is a medication used in veterinary medicine to address various conditions in animals, ranging from the prevention of uric acid and calcium oxalate uroliths (stones) in dogs to treating leishmaniasis in dogs and cats. Additionally, it has been employed off-label to manage gout in certain avian and reptilian species.

  • Mechanism of Action:The medication functions by reducing the production of uric acid within the body. By inhibiting the enzyme xanthine oxidase, Allopurinol effectively decreases the formation of uric acid, thereby aiding in the prevention of urinary stone formation.

  • Administration and Formulation:Allopurinol typically comes in tablet form and is administered orally to animals. For avian patients, it may also be added to drinking water. It can be given with or without food, although administering it with a small amount of food is recommended if an animal experiences vomiting or discomfort when taken on an empty stomach.

  • Dosage and Timing:Effects of Allopurinol may not be immediately apparent and can take several weeks to manifest. In some cases, improvement may not be visibly obvious. Ensuring that the animal has access to fresh water during treatment is crucial. If a dose is missed, it should be administered as soon as possible. However, it is advised to skip the missed dose and resume the regular dosing schedule if it is nearing the next scheduled dose.

  • Side Effects and Considerations:Side effects from Allopurinol are uncommon in dogs and cats, although some animals may experience vomiting or other signs of gastrointestinal upset, such as lack of appetite or diarrhea. In dogs receiving higher doses, there is a risk of developing certain types of bladder stones known as xanthine stones. Caution should be exercised when administering Allopurinol to animals with pre-existing liver or kidney issues. It is not recommended in red-tailed hawks and should be approached cautiously in other raptors. Safety in breeding, pregnant, or nursing animals has not been established.

  • Long-term Use and Dietary Considerations:When utilized for the long-term prevention of stones in dogs, a low-purine diet is often recommended with Allopurinol therapy to further mitigate the risk of stone formation.

Allopurinol is a valuable tool in veterinary medicine for managing conditions related to uric acid production in animals. While generally well-tolerated, careful monitoring and consideration of potential side effects are essential to its administration, ensuring the well-being of the treated animals.

Allopurinol is a fast-acting prescription oral tablet, intended to prevent and dissolve urate bladder stones. Allopurinol is a xanthine oxidase inhibitor, which means it inhibits the production of uric acid, preventing the build up of the crystals in the urine that cause bladder and kidney stones.

Allopurinol works by preventing the conversion of protein purines to uric acid. While Allopurinol prevents bladder and kidney stones, it can also dissolve stones that have already formed, and also treats infection due to the blood parasite Leishmania.

Allopurinol is the generic alternative to Zyloprim.

  • Kidney Health Pharmacy
  • Care Wellness Philosophy
  • Ivermectin Sensitivity Allergies
  • Prescription Pharmacy Type
  • Oral Application
  • Dog Pet Type

What Are the Side Effects of Allopurinol in Dogs?

Allopurinol is a safe, veterinary-recommended, and effective medication for dogs. It helps prevent bladder and kidney stones in dogs. It dissolves existing urate bladder stones as well. While the drug is considered safe for dogs, it might cause side effects, such as diarrhea, gastrointestinal distress, dizziness, and drowsiness. Also, it can trigger symptoms of an allergic reaction, including facial swelling, rashes, blood in the urine, painful urination, nausea, and vomiting. It's important to consult a veterinarian if your notice any unusual symptoms or behavior in your dog after administering allopurinol. Additionally, make sure you inform them about any other medication your dog is currently taking.

Will Allopurinol Hurt My Dog?

Allopurinol is a powerful xanthine oxidase inhibitor that helps prevent and control urate bladder stones in dogs. It controls uric acid production, thus eliminating the chances of crystal formation in your dog's kidneys and bladder. As long as you follow your vet's instructions regarding the dosage and timing of administering allopurinol, the medication won't hurt your dog. However, it's important to watch out for signs of allergic reactions, such as swelling of the face and tongue, excessive vomiting, and nausea. Also, allopurinol is known to have drug interactions with specific medications, such as amoxicillin, ampicillin, warfarin, azathioprine, etc. If your dog is taking any of these medications, don't forget to let your veterinarian know before they prescribe allopurinol.

Can Cats Take Allopurinol?

Yes. Allopurinol can be administered to both cats and dogs for the treatment of kidney and bladder stones. It inhibits uric acid production and prevents the formation of crystals in the urine. Side effects or allergic reactions to allopurinol are uncommon in cats and dogs. Nevertheless, it's always a good idea to consult your vet before administering the medication to your cat.

Is There an Over the Counter Substitute for Allopurinol?

Allopurinol is a prescription medication that isn't sold over-the-counter in the U.S. Currently, there are now known OTC substitutes for allopurinol. Make sure you consult your vet before considering any allopurinol substitutes for your dog.

Can Allopurinol Cause Bladder Stones?

No. Allopurinol is a xanthine oxidase inhibitor. That means the drug minimizes uric acid production and thus, helps prevent the formation of crystals in urine. That's the reason allopurinol is used for the treatment of bladder and kidney stones in dogs. Allopurinol can also be given to cats. However, if your dog exhibits any signs of chronic kidney disease or bladder stones, it's always a good idea to consult your vet before administering allopurinol.

Which Is Better - Colchicine or Allopurinol?

Both allopurinol and colchicine can be used for the treatment of inflammation and pain resulting from gout attacks. However, long-term use of colchicine can result in blood disorders. On the other hand, allopurinol works by inhibiting uric acid production and crystal formation. That makes allopurinol a safer and more effective choice for preventing and dissolving uric acid crystals and bladder stones.

Is There Anything Better Than Allopurinol?

Allopurinol is a generic alternative to Zyloprim. It's a potent medication that treats urate bladder stones and gout attacks in dogs. While you'll find a few similar medications on the market, allopurinol is more effective. Also, adverse reactions to allopurinol are uncommon in dogs. It is, however, always important to talk to your vet before giving the medication to your dog.

Does Allopurinol Damage the Liver?

Short-term use of allopurinol won't cause any damage to your dog's liver. The most common side effects include symptoms of gastrointestinal distress. However, if you administer allopurinol to your dog over a longer duration, it can cause acute liver injury. But the occurrence of such liver damage is extremely rare. Also, it's more likely in dogs with allopurinol hypersensitivity syndrome. Make sure you consult your vet before using long-term allopurinol treatment for your dog.


Seek emergency veterinary aid if your pet experiences an allergic reaction such as, hives, difficulty breathing, swelling of the face, lips, tongue or throat, blood in the urine, pain when urinating, a rash, eye irritation, fever, chills or joint aches or severe nausea or vomiting. Consult veterinarian if your pet experiences upset stomach or diarrhea, dizziness or drowsiness or an acute attack of arthritis, or anything out of the ordinary.

Ampicillin or amoxicillin may increase the risk of rash development. Notify your veterinarian if your pet is being given a thiazide diuretic, azathioprine, drugs used to treat cancer, cyclosporine, warfarin or theophylline. Consult to your veterinarian before administering additional prescription or over the counter medications.

Administer Allopurinol to the exact specifications prescribed by veterinarian. Give Allopurinol orally with water and food.


All Weights: 5mg per pound of body weight, once daily with food

Ask your veterinarian or consult with one of our pet care specialists at 1-800-844-1427.

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian. Always seek the advice of your veterinarian or other qualified professional with any questions you may have regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website. Our medications are FDA approved and/or EPA regulated when and as required by law.

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Related Articles

Xanthine Bladder Stones in Cats: Causes, Symptoms, and Treatment

What Leads to Xanthine Bladder Stones in Cats and How To Get Rid of It

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Using Allopurinol for Urate Stones in Dogs

An Antibiotic for Treating Bladder Stones in Dogs

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