Hydroxyurea in Dogs

A dog taking hydroxyurea will require regular vet visits to monitor his progress.
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Hydroxyurea is registered for human use, sold under the brand names of Mylocel and Hydrea. Though the Food and Drug Administration does not recognize its use for animals, veterinarians prescribe hydroxyurea for specific conditions. It's a chemotherapeutic drug, meaning it's effective at destroying malignant cells and tissues.


Hydroxyurea is an antineoplastic drug, meaning it's turned loose on neoplasms, or abnormal tissue growth. In veterinary medicine, it's often used to treat tumors, even though the FDA hasn't approved it for use in animals. The FDA permits veterinarians to prescribe hydroxyurea as an extra-label drug. It's available in pill form, and your vet will determine the appropriate dose for your dog based on his weight and condition.

Blast the Neoplasm

Because hydroxyurea is a chemoterapeutic drug, it's useful for a number of conditions, including melanoma, ovarian carcinoma, conditions where there are too many red blood cells present in your pup such as polycythemia and erythrocytosis, mast cell tumors and chronic myelocytic leukemia, a cancer of the bone marrow's blood forming cells. It's also prescribed to curb primary squamous cell carcinoma in the neck and head.

Possible Side Effects

Animals tend to tolerate hydroxyurea fairly well, but a few side effects are possible. Mild complications include skin rash or ulcers, decreased appetite, hair loss, redness in the skin, vomiting, diarrhea, and inflammation or soreness of the mouth. Some dogs become more vulnerable to urinary tract infections. White blood cell production may also decrease, resulting in anemia. Hydroxyurea can affect kidney function, so dogs with pre-existing kidney issues should be closely monitored. The vet will likely monitor your pup's platelet count, white blood cell count, blood urea nitrogen, creatinine and liver levels before, during and after treatment with hydroxyurea.

Handle With Care

Your dog's use of hydroxyurea will depend on why he's taking it and how he responds. Some dogs take the medication for the rest of their lives while others are weaned off over time. As well, the appropriate dosage for your dog may change over time as his condition dictates. Regardless of his schedule, you should exercise caution when you give him his meds. Take care to avoid contact with your skin -- you may want to wear disposable gloves -- and wash your hands thoroughly after giving your dog his medicine.