Pet Owners


My cat has been diagnosed with a blood clot in the aorta (“saddle thrombus”); can I join the study?

–If your veterinarian has diagnosed your cat with an abnormal blood clot, your cat may be eligible for inclusion in the study.

–For full inclusion, your cat must have recovered from the initial clot episode, and must be examined by a board-certified veterinary cardiologist. You may find a cardiologist near you through your veterinarian, or by searching

–If your cat developed a clot for a reason unrelated to cardiac disease, he or she is not eligible.

–You should be comfortable administering oral medication to your cat.

What benefits will I receive for taking part in the study?

–The study will provide your cat with free anticoagulant medication for up to 2 years.

–The study will provide some monetary support to defray the cost of periodic examinations by a veterinary cardiologist.

What do I need to do as part of the study?

–Study medications will be dispensed in 2-month intervals. In order to receive the subsequent 2-month supply, you will need to fill out a survey online or by phone that poses questions about your cat’s activity and quality of life. Following completion of the survey, medications will be mailed to you, so this contact should be made about 1.5 months after the previous medication delivery

–In addition, you will be required to have your cat’s heart evaluated by a board-certified veterinary cardiologist at 2 months, 6 months, 12 months, and 18 months after your cat has been entered in the study. We will provide some funds ($150 per visit) to help offset the cost of these examinations.

–A small amount of blood (1 tsp) will be collected at these visits to monitor drug levels in your cat’s blood. Additional blood samples may be collected, as determined by your veterinarian.

–While receiving the study medication, you must not give your cat other medications that can interfere with blood clotting (e.g. aspirin, heparin), as these could cause adverse interactions with the study medication.

–Be in regular communication with the study coordinators, using a dedicated phone number. Any changes in your cat’s health should be conveyed immediately to the coordinators. We are also available to speak to your veterinarian at all times about potential drug or disease interactions.

–If your cat experiences any adverse reactions to the medication, you must notify the study coordinators immediately.

–If your cat develops any disease, including another blood clot, or congestive heart failure, you must notify the study coordinators immediately.

How do I receive the first supply of study medication?

 — Upon enrollment of a cat into the study, we ask that a veterinarian who has examined the cat (either the primary care veterinarian or the cardiologist) write two prescriptions: one for rivaroxaban and one for clopidogrel. Once the study director is in receipt of the prescriptions, your cat will be randomized to receive one or the other, and only the appropriate prescription will be filled, and mailed to you.

Can my cat have surgery or oral health (dental) treatments on a cat that is taking a study drug?

–Maybe. There are specific guidelines in human medicine regarding the timeline for emergency or planned surgery for each study drug. Please contact us by phone or email if your cat requires surgery or an invasive procedure.

 Will I still be able to visit my regular veterinarian while my cat is receiving the study drug?

 –Absolutely! We expect that cats will continue to visit their family veterinarians for routine care and examinations. Your veterinarian will also have the ability, by phone or email, to contact the study coordinators with any concerns.

What are the possible side effects of the study drugs?

— These medications have been administered safely to healthy cats, and it is not anticipated that your cat will experience any adverse effects, but it is important to be aware of them. The study drugs are both drugs that decrease the ability of your cat to form blood clots. Consequently, you may notice delayed clotting if you cat cuts itself. Side effects that require immediate evaluation by a veterinarian include the appearance of bruising, nose bleeds, or blood in the stool or urine, or small, pin-point red areas on the ears, gums, or inner thighs. If you notice these, please do not give the next dose of study medication and contact your veterinarian and the study coordinators immediately.

What will happen at the completion of the study?

 — At the end of 2 years, you may elect to continue to administer the study medication, or can elect to pursue a different regimen. Because the rivaroxaban used in the study will be compounded by a commercial pharmacy, you will have the opportunity to continue to purchase and receive rivaroxaban from this source. If your cat has been receiving clopidogrel, this medication is available from many commercial pharmacies, who will just require a valid prescription.