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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

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

Frequency

Variable (see notes)

🐈

Cat

Used for polycythemia vera and hypereosinophilic syndrome

Dose

25 mg/kg

Route

Frequency

q24h → q48–72h (taper)

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

💊

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

Educational reference only

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.

Educational reference only

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.

Educational reference only

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