Home/Medicines/Allopurinol
All medicines

Allopurinol

Prescription
Xanthine oxidase inhibitor
Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
4 available
Interactions
1 documented
Formulations
2

Mechanism of action

Inhibits xanthine oxidase, the enzyme that converts hypoxanthine to xanthine and xanthine to uric acid; reduces uric acid production and is used to prevent urate urolithiasis and treat Leishmania

At a glance

Class
Xanthine oxidase inhibitor
Schedule
Prescription
Storage
Below 25°C, protect from moisture and light

Dosing

🐕

Dog

Urate urolithiasis prevention (Dalmatians, portosystemic shunts), leishmaniasis adjunct
Dose
10–20 mg/kg
Route
PO
Frequency
BID to TID
Max dose
300 mg/dose; 900 mg/day
Duration: Long-term for urate prevention; with antimonials for Leishmania
🐈

Cat

Urate urolithiasis (rare)
Dose
10–15 mg/kg
Route
PO
Frequency
SID
Max dose
100 mg
Duration: Long-term as needed
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Formulations

💊

Tablet — 2

Strength
100mg
Available in India
Strength
300mg
Available in India

Storage

Below 25°C, protect from moisture and light

Safety

Absolute contraindications — do not use

  • Known hypersensitivity to allopurinol
  • Concurrent azathioprine
    Allopurinol inhibits xanthine oxidase metabolism of azathioprine — FATAL myelosuppression; reduce azathioprine dose by 50–75% if absolutely necessary
    azathioprine6-mercaptopurine

Adverse effects

Common
Xanthine urolithiasis (if purine intake not restricted)
Serious
Hepatotoxicity
Vasculitis
Xanthine stone formation

Monitoring parameters

Serum uric acidUrinalysisImaging for stonesHepatic enzymesLow-purine diet compliance
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Interactions

Major — 1

Azathioprine
major
Allopurinol inhibits xanthine oxidase which metabolizes azathioprine's active metabolite 6-MP. Concurrent use causes severe 6-MP accumulation and life-threatening myelosuppression.
Management: Reduce azathioprine dose by 25-33% when combined with allopurinol. Monitor CBC every 1-2 weeks. Some references recommend avoiding combination entirely.
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Brands

International

Zyloprim
Prometheus
Aloprim
Various

India

Zyloric
GSK India
Allopurinol
Cipla

FAQs

Frequently asked questions

›What is Allopurinol?
Allopurinol is a xanthine oxidase inhibitor used in pets. Inhibits xanthine oxidase, the enzyme that converts hypoxanthine to xanthine and xanthine to uric acid; reduces uric acid production and is used to prevent urate urolithiasis and treat Leishmania
›What is Allopurinol used for in pets?
Allopurinol is used in veterinary medicine for: Urate urolithiasis prevention (Dalmatians, portosystemic shunts), leishmaniasis adjunct; Urate urolithiasis (rare).
›What is the Allopurinol dose for dogs?
For dogs, Allopurinol is typically dosed as follows — Urate urolithiasis prevention (Dalmatians, portosystemic shunts), leishmaniasis adjunct: 10–20 mg/kg PO BID to TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Allopurinol dose for cats?
For cats, Allopurinol is typically dosed as follows — Urate urolithiasis (rare): 10–15 mg/kg PO SID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What are the side effects of Allopurinol?
Common: Xanthine urolithiasis (if purine intake not restricted). Serious (call your vet immediately): Hepatotoxicity, Vasculitis, Xanthine stone formation.
›Does Allopurinol need a prescription?
Yes. Allopurinol is a prescription medication and should only be administered under veterinary supervision.
›When should Allopurinol not be used?
Do not use Allopurinol if: Known hypersensitivity to allopurinol; Concurrent azathioprine.
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

References

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

  • Plumb's Veterinary Drug Handbook
  • Withrow & MacEwen's Small Animal Clinical Oncology
  • Merck Veterinary Manual
  • NRC Nutrient Requirements of Dogs and Cats
  • Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

  • ASPCA Animal Poison Control Center Guidelines
  • AAHA Diabetes Management Guidelines
  • ASPCA Poison Control Guidelines
  • RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

  • EPIC Study (J Vet Intern Med 2016)
  • JVIM FAT CAT Study

Regulatory & approvals — 1

  • CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

  • Washington State University VCPL MDR1 Database
Need help? 💬
Chat with us on WhatsApp