Anti‐platelet therapy in small animal medicine

Abstract

Thromboembolism is a significant complication in many commonly encountered diseases, and can be a devastating sequel to otherwise treatable conditions. Platelets play an essential role in the hemostatic process and, consequently, are associated with thrombus formation. Platelets adhere to denuded vascular subendothelium, recruit additional platelets and cells, aggregate, and provide the catalytic surface for thrombin production and fibrin formation. Therapy to prevent unwanted thrombus formation and thromboembolic crises is essential in the management of hypercoagulable patients. Unfortunately, many of the medications used in veterinary medicine that inhibit or modulate coagulation factors, such as the heparins, are cost prohibitive, only effective when administered by injection or require frequent drug monitoring, and are therefore poor choices for long term at home therapy. While the role of the platelet in pathologic thrombus formation is not fully understood, veterinarians often resort to anti-platelet therapy in the management of patients at risk for thromboembolic complications, because many anti-platelet medications are inexpensive, require minimal drug monitoring, and can be given orally. The aim of this review is to discuss the anti-platelet therapies that are currently being used or being considered for use to inhibit platelet function and reduce thromboembolic complications in hypercoagulable dogs and cats.

A Remote Assay for Measuring Canine Platelet Activation and the Inhibitory Effects of Antiplatelet Agents

“…However, mf values in this cohort were higher than unstimulated values with one value substantially higher. This observed difference could indicate suboptimal inhibition of platelet activity by aspirin in these dogs, perhaps reflecting inadequate dosing . Despite these differences, there was no significant difference between conditions A and C. The failure to reach significance could be due to the small numbers in the treated dog group and represent a Type II statistical error.…”

“…The ability of antiplatelet medications to prevent or reduce thrombotic events is unclear if we are unsure of the effect individual dose. There is robust evidence in the veterinary literature that the dose/efficacy of aspirin is frequently suboptimal . Whether this applies to clopidogrel is unclear; however, dose adjustments might be necessary in cats undergoing long‐term treatment .…”

“…In humans, genetic polymorphisms significantly influence the beneficial and undesirable effects of these medications . This phenomenon is also recognized in dogs carrying the MDR‐1 mutation, which may impact clopidogrel therapy due to the ABCB1 gene's role in intestinal uptake . In humans, genetic polymorphisms lead to significant differences in the efficacy of oral antithrombotic drugs .…”

Comparison of Multiplate, Platelet Function Analyzer‐200, and Plateletworks in Healthy Dogs Treated with Aspirin and Clopidogrel

“…Aspirin inhibits cyclooxygenase (COX) hence preventing thromboxane A 2 synthesis . Aspirin resistance has been well described in humans, with an estimated prevalence of 8–45% .…”

Abnormal platelet activity in dogs and cats – impact and measurement

“…These pharmacotherapies can be categorised as: ADP receptor antagonists, thromboxane inhibitors and the newer α IIb β 3 integrin receptor antagonists. Their mechanisms and duration of action are summarised in Table 4 and more in depth information is available in a couple of review articles (Lunsford & Mackin 2007, Thomason et al 2016). The interested reader is also referred to a recent consensus statement which summarises the indications for antithrombotic medication using the current evidence available (Goggs et al 2019).…”