Brand Name: Plavix

Available in 75 mg & 300 mg tablets

Background

There are many diseases that increase the body's tendency to form blood clots. This tendency is a problem when abnormal blood clots form, break off, and lodge in places where they block off (occludes) normal blood flow. Further, the body's natural mechanisms to dissolve blood clots are inherently inflammatory, and the resulting biochemicals can be dangerous if there are a large number of blood clots dissolving at once. The diseases that result from abnormal blood clotting, vessel occlusion with clots, and inflammation from clot dissolution are called thromboembolic or thrombotic diseases.

Examples of such diseases in veterinary medicine would include the feline condition now known as FATE, where a large blood clot forms in the heart, a small piece of the clot breaks off and then lodges in the aorta (the large artery that travels the length of the body) right where it branches to serve the rear legs. The circulation to the rear legs is painfully disrupted, and while many cats survive this episode and regain function in their rear legs, they are at risk for future episodes. In cats with heart disease, there are certain findings on ultrasound that suggest a cat is at risk for forming abnormal clots even when they have not done so before. Either suggestion warrants medication to reduce clotting tendency.

In dogs, immune-mediated hemolytic anemia, where the immune system wrongly attacks the body's own red blood cells, carries a high mortality rate because of thromboembolic disease. In these patients, medication to reduce blood clotting can be life-saving.

In the past, the only medication option was low-dose aspirin to inactivate platelets, the blood cells responsible for clotting blood. There is still controversy as to whether the inexpensive, decades-old medication works just as well as the new drug. Both drugs inactivate platelets, but they do so by different routes. A large study of cats at risk for thromboembolic disease (the FATCAT study), however, clearly showed improved survival rates in the clopidogrel group over the aspirin group. Similar studies in canine disease are lacking, but the results of the FATCAT study has made this medication more popular in both dogs and cats to treat and prevent thromboembolic disease.

How this Medication is Used

This medication is used once daily in patients deemed at risk for thromboembolic disease. It may be given with or without food. If a dose is accidentally skipped, give it when it is remembered and time the next dose accordingly. Do not double up on the next dose.

Side Effects

The most common side effects relate to an upset stomach (appetite loss, vomiting, diarrhea). Giving clopidogrel with food generally alleviates these symptoms.

Inappropriate bleeding is always possible with medications that reduce clotting. It is important to watch for black or bloody stools, bruising, and nose bleeds.

Anemia (red blood cell deficiency) not associated with bleeding has been reported as well, although rarely.

Interactions with Other Drugs

Bleeding risk is increased when clopidogrel is combined with aspirin. Many patients take these medications together.

The following medications interfere with the actions of clopidogrel, potentially making it less effective: calcium channel blockers (usually given as heart medicines), the "azole" antifungals (ketoconazole, itraconazole, fluconazole, etc.), chloramphenicol (an antibiotic), and cimetidine (an antacid).

Non-steroidal anti-inflammatory medications may increase the risk of bleeding when combined with clopidogrel, as can concurrent use of clopidogrel with serotonin reuptake inhibitors (such as fluoxetine).

Concerns and Cautions

As noted above, if nausea or GI side effects result, try giving clopidogrel with food. If this does not help, notify your veterinarian.

Platelet function returns to normal five to seven days after stopping.

If you think there is abnormal bleeding, discontinue the medication and notify your veterinarian.