Home/Medicines/Hydroxyurea
All medicines

Hydroxyurea

Prescription
Ribonucleotide Reductase Inhibitor (Chemotherapy)
Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
2 available
Interactions
1 documented
Formulations
1

Mechanism of action

Inhibits ribonucleotide reductase, blocking DNA synthesis without affecting RNA or protein synthesis. Cell-cycle specific (S-phase). Used for myeloproliferative disorders.

At a glance

Class
Ribonucleotide Reductase Inhibitor (Chemotherapy)
Schedule
Prescription (Chemotherapy)
Storage
Store at room temperature 15–30°C; handle capsules with care (wear gloves when opening)

Dosing

🐕

Dog

Used for polycythemia vera, chronic myeloid leukemia, meningiomas
Dose
50 mg/kg
Route
PO
Frequency
Variable (see notes)
🐈

Cat

Used for polycythemia vera and hypereosinophilic syndrome
Dose
25 mg/kg
Route
PO
Frequency
q24h → q48–72h (taper)

Formulations

💊

Other — 1

Strength
—

Storage

Store at room temperature 15–30°C; handle capsules with care (wear gloves when opening)

Safety

Monitoring parameters

CBC weekly initially, then every 2–4 weeksHepatic functionTumor/disease response

Interactions

Major — 1

Azathioprine
major
Both cause myelosuppression via different mechanisms. Combined: severe additive bone marrow suppression.
Management: Avoid. If switching, monitor CBC closely during transition.

Brands

Other markets

Hydrea
Droxia

FAQs

Frequently asked questions

›What is Hydroxyurea?
Hydroxyurea is a ribonucleotide reductase inhibitor (chemotherapy) used in pets. Inhibits ribonucleotide reductase, blocking DNA synthesis without affecting RNA or protein synthesis. Cell-cycle specific (S-phase). Used for myeloproliferative disorders.
›What is Hydroxyurea used for in pets?
Hydroxyurea is used in veterinary medicine for: Used for polycythemia vera, chronic myeloid leukemia, meningiomas; Used for polycythemia vera and hypereosinophilic syndrome.
›What is the Hydroxyurea dose for dogs?
For dogs, Hydroxyurea is typically dosed as follows — Used for polycythemia vera, chronic myeloid leukemia, meningiomas: 50 mg/kg PO Variable (see notes). Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Hydroxyurea dose for cats?
For cats, Hydroxyurea is typically dosed as follows — Used for polycythemia vera and hypereosinophilic syndrome: 25 mg/kg PO q24h → q48–72h (taper). Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›Does Hydroxyurea need a prescription?
Yes. Hydroxyurea is a prescription medication and should only be administered under veterinary supervision.

References

References

Textbooks & handbooks

  • Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
  • Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
  • Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
  • National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
  • The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/

Clinical guidelines & consensus

  • Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
  • American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.

Journals & peer-reviewed studies

  • Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
  • Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
  • ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control

Regulatory & approvals

  • Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/

Databases

  • Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
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 →