Warfarin

Major Uses

Warfarin is an anticoagulant that is primarily used to treat cats, dogs, and horses over a long period of time for thrombotic conditions. It is also helpful in preventing the recurrence of thrombotic conditions.

Common Precautions

Warfarin should not be used in animals with preexisting hemorrhagic tendencies or diseases, or those undergoing or contemplating eye or CNS surgery, surgery of large/open surfaces, or major regional lumbar block anesthesia. Patients with active bleeding from GI, respiratory, or GU tract should also not use warfarin. Caution should be used when giving to patients with aneurysm, cerebrovascular hemorrhage, acute nephritis, blood dyscrasias, hepatic insufficiency, uncontrolled or malignant hypertension, pregnancy, visceral carcinomas, and pericardial effusion

The most common negative side effect associated with warfarin is dose-related hemorrhages, which commonly cause clinical signs of anemia, weakness, thrombocytopenia, hematomas and ecchymoses, hematemesis, epistaxis, hematuria, melena, hemathrosis, hematochezia, hemathorax, intracranial and/or pericardial hemorrhage, and death.

Warfarin should not be used in animals with a known allergy or hypersensitivity to the drug. A veterinarian should be contacted immediately if an overdose is suspected, the symptom of which is most commonly a life-threatening hemorrhage.

Storage

Warfarin should be kept at room temperature and stored in a container that is childproof and resistant to light. The powder form should be protected from light and used immediately after reconstituting. Warfarin should be kept out of the reach of children and pets.

Administration

For treating dogs, a typical dose of warfarin is .22 mg/kg once or twice daily. For cats, a typical dose is between .06-.5 mg/kg once daily. For horses, a common dose ranges from .0198-.58mg/kg once daily. Should a dose of warfarin be missed, it should be administered as soon as possible. If it is nearing time for the next scheduled dose, the missed dose should be skipped and the regular dosing schedule should be continued. Two doses of warfarin should not be administered at the same time.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.