Allopurinol
Also known as: Zyloprim, Aloprim, Zyloric, Zylapour
> **Important:** Unless otherwise directed by your veterinarian, administer this medication **after meals** (usually about 1 hour after) to minimize stomach upset. * **Dietary Management:** If your pet is being treated for urate stones, strictly follow the **low-purine diet** prescribed by your vet. Giving this medication without the proper diet can lead to the formation of a different type of stone (xanthine). * **When to Call the Vet:** Notify your veterinarian immediately if your animal develops a **skin rash**, becomes unusually **lethargic**, or appears ill. * Ensure your pet always has access to plenty of fresh drinking water to help flush the urinary system.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Urate uroliths (dissolution)
- Urate uroliths (prevention)
- Urate uroliths (dissolution and prevention)
- Leishmaniasis (First line treatment)
- Leishmaniasis (Second line treatment)
- Leishmaniasis
- Leishmaniasis (Alternate protocol alone)
- Leishmaniasis
- Leishmaniasis (with renal insufficiency)
- Leishmaniasis
- Uric acid urolithiasis (Dissolution)
- Uric acid urolithiasis (Prevention)
- Leishmaniosis
How it is given
Possible side effects
- Xanthine urolithiasis (especially with high doses or non-restricted diets)
- Hypersensitivity reactions (rash, erythema)
- Lethargy
- Gastrointestinal upset
- Hepatotoxicity (rare)
- Bone marrow suppression (rare)
Cautions & contraindications
- Known hypersensitivity to allopurinol
- Red-tailed hawks (anecdotal reports of severe toxicity)
- Prolonged high doses of allopurinol may result in **xanthine uroliths**; it is highly recommended to use concurrently with a low-purine diet for urolith management. Use with caution and consider dose reduction (e.g., 5 mg/kg PO twice daily) in patients with **renal insufficiency**.
Drug interactions
- Chlorpropamide: May increase risks for hypoglycemia and hepato-renal reactions
- Cyclophosphamide: Increased bone marrow depression may occur
- Cyclosporine: Allopurinol may increase cyclosporine levels
- Diuretics (Furosemide, Thiazides, Diazoxide) and Alcohol: Can increase uric acid levels, antagonizing allopurinol's effect
- Oral Anticoagulants (e.g., Warfarin): Allopurinol may reduce the metabolism of warfarin thereby increasing its effect
- Trimethoprim/Sulfamethoxazole: Thrombocytopenia has occurred in a few human patients when used concurrently
- Uricosuric Agents (e.g., Probenecid, Sulfinpyrazone): May increase the renal excretion of oxypurinol and thereby reduce xanthine oxidase inhibition; additive effects on blood uric acid may be beneficial
- Urinary Acidifiers (e.g., Methionine, Ammonium Chloride): May reduce the solubility of uric acid in the urine and induce urolithiasis
- Azathioprine: Allopurinol inhibits the metabolism of azathioprine, leading to severe, potentially fatal myelosuppression.
- Mercaptopurine: Allopurinol inhibits the metabolism of mercaptopurine, significantly increasing toxicity risk.
Frequently asked questions
What is Allopurinol used for in pets?
> **Important:** Unless otherwise directed by your veterinarian, administer this medication **after meals** (usually about 1 hour after) to minimize stomach upset. * **Dietary Management:** If your pet is being treated for urate stones, strictly follow the **low-purine diet** prescribed by your vet. Giving this medication without the proper diet can lead to the formation of a different type of stone (xanthine). * **When to Call the Vet:** Notify your veterinarian immediately if your animal develops a **skin rash**, becomes unusually **lethargic**, or appears ill. * Ensure your pet always has access to plenty of fresh drinking water to help flush the urinary system.
Is Allopurinol safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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