Warfarin
“This page provides important general information for pet owners whose animals have been prescribed Warfarin for pets in Perth during a consultation by Dr Noor.”
Warfarin
(war-far-in)
Description:
This medicine is used to thin the blood.
Other Names for this Medication:
- Coumadin®
Common Dosage Forms:
- For animals: there are no standard veterinary forms.
- For people: tablets are available in 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg.
This handout does not include every possible detail about this medicine. It is meant to address common questions, but it does not replace medical guidance. If you need more details or have questions about this medicine, contact your veterinarian or your pharmacist.
Key Information
- Many medicines and some foods can affect how warfarin works. These interactions can either raise the chance of bleeding or make warfarin less effective at preventing clots. Before you start any new medicine (including non-prescription/OTC products) or before you stop any medicine your animal is already taking, speak with your veterinarian or pharmacist.
- Keep your animal away from situations where injury, cuts, or wounds could happen, because severe bleeding may occur. If you notice unusual bleeding, contact your veterinarian right away.
- While your animal is on this medicine, your veterinarian will need to do regular checkups and blood tests. These follow-up visits are important and should not be missed.
- People who are pregnant should be careful when handling this medicine.
How is this medication useful?
Warfarin is used to reduce the chance of blood clots forming in animals that have problems with blood flow. This medicine is approved for use in people, but it is not officially approved for use in animals. In some situations, veterinarians may prescribe a medicine like this for different species or for different health problems. You can talk with your veterinarian about why this choice is being used.
What should I tell my veterinarian to see if this medication can be safely given?
Many factors can change how this medicine works in your animal. Make sure you and your veterinarian discuss the points below so you can decide on the safest plan.
- Other medicines may react with warfarin. Tell your veterinarian and pharmacist about everything your animal receives, including vitamins, supplements, and herbal products. Also share how much you give and when you give each one.
- Tell your veterinarian about any health problems your animal has now, or has had before.
- If your animal has had treatment in the past for the same problem, tell your veterinarian what was used and whether it helped or did not help.
- If your animal is pregnant or nursing, discuss the possible risks of using this medicine.
- Tell your veterinarian and pharmacist if your animal has ever had medicine-related problems before, including allergic reactions, not wanting to eat, loose stool/diarrhea, itching, or hair loss.
How long until I will know if this medication is working, and how long will the effects of this medication last?
This medicine is expected to begin working within 1 to 2 hours. However, you will not be able to see its effects just by looking at your animal. Your veterinarian will need to do tests to check whether it is working as intended.
The effect does not last long. It stops working within about 24 hours. The helpful effect may last longer if your animal’s kidneys and/or liver are not working well.
When should this medication not be used or be used very carefully?
No medicine is completely safe for every patient. Your veterinarian will talk with you about any concerns that apply to your animal.
This drug should be used WITH CAUTION:
- If your animal has any of the issues listed below, discuss with your veterinarian how the risks compare with the possible benefits.
- If there are bleeding concerns (for example, stomach sores/ulcers or damaged blood vessels), or if the animal is going to have surgery.
- If the animal has anemia, meaning the red blood cell level is too low.
- If the animal is pregnant.
- If the animal has liver disease.
- If the animal is a working animal or a performance horse, because cuts or bruises can lead to bleeding that may be difficult to control.
What are the side effects of this medication?
Side effects that may be serious or may point to a serious problem:
- If you notice any bleeding, contact your veterinarian immediately.
- Bleeding is the main side effect of warfarin. It increases the chance of bleeding problems. This can show up as nosebleeds, bruising, vomit that contains blood, stool that contains blood, or stool that looks black and tar-like. Bleeding can also lead to anemia (too few red blood cells) or major blood loss.
If my animal gets too much of this medication (an overdose), what should I do?
- Taking too much warfarin can be dangerous. It is essential to follow the prescription directions exactly, because an overdose can cause serious bleeding.
- If you see an overdose happen, or you think one may have happened, contact your veterinarian right away or call an animal poison control service immediately for instructions.
- There is a consultation fee for these services.
How should this medication be given?
- For this medicine to work properly, it must be given exactly the way your veterinarian ordered it. Always read the prescription label to confirm you are giving it correctly.
- Warfarin is given by mouth one time each day, and it should be given at roughly the same time every day.
- In store-bought warfarin tablets, the active medicine may not be spread evenly through the tablet. If your veterinarian tells you to give 1/2 or 1/4 of a tablet, crush the entire tablet first, stir the powder so it is well mixed, and then give 1/2 or 1/4 of the mixed powder. Another option may be to have a pharmacist prepare capsules with the exact dose, or make a liquid form to help you give the correct amount.
- You may give this medicine with food or without food. If your animal vomits or seems unwell after getting it on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian.
- If your animal is using a specially made (compounded) liquid form, measure it with care. Your veterinarian or pharmacist can provide special spoons or dosing syringes to help with accurate measuring.
- If giving the medicine is difficult, contact your veterinarian or pharmacist for ways to make dosing easier and to lower stress during medicine time.
- This medicine may be used for different lengths of time depending on the situation. Make sure you understand how long your veterinarian wants you to keep giving it. You may need refills before the full course is finished. Do not stop this medicine without speaking to your veterinarian, because there may be important reasons to continue.
What should I do if I miss giving a dose of this medication?
- If you forget a dose, give it as soon as you remember.
- If it is almost time for the next scheduled dose, do not give the missed dose.
- Instead, give the next dose at the regular time.
- Then continue with the normal schedule.
- Do not give two doses at once and do not give extra doses.
How should I store this medication?
- Keep this medicine at room temperature, in the original prescription container or in an approved pill organizer.
- If your veterinarian or pharmacist prepared a special (compounded) form for your animal, follow the storage directions and the expiration date provided for that product.
- Store it where children and other animals cannot reach it.
Can handling this medication be hazardous to me, my family, or other animals?
- Because this medicine has a higher chance of causing birth defects, people who are pregnant must take extra care to avoid accidentally taking it.
- When giving doses or touching the medicine, wear disposable gloves. Do not breathe in dust that may come from tablets that are split or crushed.
- If powder or liquid containing this medicine gets on skin or in the eyes, wash or rinse the area thoroughly right away, and then contact your doctor.
How should I dispose of this medication if I don’t use it all?
- Do not put this medicine into the toilet or pour it into a sink.
- If there is a local medicine take-back program, use that option.
- If there is no take-back program, combine the medicine with used coffee grounds or cat litter so it is unappealing to children and animals and not recognizable to someone searching through trash. Put the mixture into a sealable plastic bag to prevent leaks, and place it in the household trash.
- Do not keep extra medicine for later use, and do not give it to anyone else.
What other information is important for this medication?
- Your veterinarian will need to recheck your animal and run blood tests from time to time while this medicine is being used. Do not skip these follow-up appointments.
- Do not let your animal be in situations where it could be hurt or cut, because serious bleeding could happen.
- Some animal competitions may not allow use of this medicine. Check the rules before entering your animal in a competition while this medicine is being given.
- If you have more questions about this medicine, contact your veterinarian or pharmacist.
“Disclaimer: The information on this page is provided as general educational material only. Every animal’s health situation is unique, and treatment decisions must be based on a full veterinary assessment. Always follow the specific instructions given during your consultation, and contact the prescribing veterinarian if you have any concerns.”