Clopidogrel

What is clopidogrel?

Clopidogrel (brand name: Plavix®) is a platelet aggregation inhibitor used to prevent abnormal blood clot formation in dogs, cats, and sometimes horses. Certain conditions such as heart disease can predispose a dog or cat to blood clots, and these blood clots can lead to other problems such as paralysis or brain injury (stroke).

In the lungs, blood clots can block the flow of blood and oxygen, causing a pulmonary embolism. In cats, this medication may also improve circulation in the lower limbs when used after a blood clot event. 

Its use in cats and dogs to prevent blood clots is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. 

“Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How is clopidogrel given?

• Clopidogrel is given by mouth in the form of a tablet or compounded liquid. Measure liquid doses carefully.
• It may be given with or without food.
• If vomiting occurs when dosed on an empty stomach, give future doses with food.
• The medication is extremely bitter, so the tablet can be put inside an empty gelatin capsule before administration to make it more palatable.

This medication should take effect within 1 to 2 hours; however, effects may not be noted outwardly, so laboratory tests may be needed to evaluate this medication’s effectiveness.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Clopidogrel may cause the following side effects:

• Stomach upset, such as vomiting, diarrhea, or lack of appetite
• Anemia (in cats receiving this medication long-term)

Serious adverse reactions may occur. If any of the following signs develop, stop giving clopidogrel and contact your veterinarian immediately:

• Bruising
• Difficulty breathing
• Blood in vomit or feces (blood can appear red or black)

In humans, the most common side effect is bleeding, and less commonly reported side effects include stomach upset and skin rashes.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately.  This moderate-acting medication should stop working in several days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE clopidogrel in pets that:

• Are allergic to it
• Have active bleeding problems

USE WITH CAUTION in pets that:

• Are pregnant or nursing

In pets that need surgery, this medication should be stopped (if possible) approximately 7 days prior to surgery. In some pets, the risk of stopping this medication versus the risk of bleeding during surgery should be considered.

Are there any drug interactions I should be aware of?

Several medications should be used with caution when given with clopidogrel, including:

• Azole antifungals
• Calcium channel blockers
• Chloramphenicol
• Cyclosporine
• Nonsteroidal anti-inflammatories (NSAIDs)
• Opioids
• Proton pump inhibitors
• Rifampin
• Rivaroxaban
• Selective serotonin reuptake inhibitors (SSRIs)
• Telmisartan
• Torsemide

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects. This testing may include platelet function testing.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store clopidogrel?

• Store this medication at room temperature (77°F or 25°C), although the medication can withstand short stints between 59°F and 86°F (15°C and 30°C).
• Protect the tablets from moisture.
• For liquid formulations, follow the storage instructions on the label, as they may vary between pharmacies.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.