Antithrombotic Drugs
Antithrombotic Drugs
Antithrombotic Drug Choices | Mechanisms of Action | Dosing Recommendations | Drug Monitoring |
|---|---|---|---|
Antiplatelet drugs | |||
Aspirin | Inhibits conversion of platelet-derived arachidonic acid to thromboxane A2, and hence thromboxane A2–induced platelet activation and aggregation Generally less efficacious than clopidogrel | Ideal dose to maximize benefit and minimize adverse effects is not known Dogs: 0.5–10 mg/kg, PO, q 24 h, long-term Cats: 81 mg/cat, PO, q 72 h, long-term | Not required, but hematocrit and renal function should be periodically monitored |
Clopidogrel | Adenosine phosphate (P2Y12) receptor antagonist | Dog: 1.1–3 mg/kg, PO, q 24 h, long-term Cats: 18.75 mg/cat, PO, q 24 h, long-term | Not required, but platelet aggregometry is useful in research settings |
Anticoagulants | |||
Rivaroxaban | Direct inhibitor of factor Xa | Dogs: 1–2 mg/kg, PO, q 24 h, long-term Cats: 0.5–1.0 mg/kg, PO, q 24 h, long-term | Not required, but rivaroxaban's specific anti-Xa activity is useful in research settings |
Dalteparin | Low-molecular-weight heparin, which binds to and potentiates the endogenous anticoagulant antithrombin, enhancing its inhibition of factor Xa Minimal factor IIa inhibition (unlike unfractionated heparin) | Dogs: 100–175 U/kg, SC, q 8 h, as needed for antithrombotic effect Cats: 75 U/kg, SC, q 6 h, as needed for antithrombotic effect | Not required, but titration to target anti-Xa activity has been investigated |
Enoxaparin | Low-molecular-weight heparin with mechanism as for dalteparin | Dogs: 0.8 mg/kg, SC, q 6 h, as needed for antithrombotic effect Cats: 0.75–1.0 mg/kg, SC, q 6 h, as needed for antithrombotic effect | Not required, but can consider titration to target anti-Xa activity |
Unfractionated heparin | Binds to and potentiates the endogenous anticoagulant antithrombin and enhances its inhibition of several coagulation factors, particularly factors Xa and IIa (thrombin) | Dogs: 100 U/kg, IV bolus, then CRI at 480–900 U/kg/d; or 150–300 U/kg, SC, q 6 h, as needed for antithrombotic effect Cats: Only SC route has been investigated; initial dose 250 U/kg, SC, q 6 h, as needed for antithrombotic effect Optimal dose likely varies from case to case | Close monitoring of either activated clotting time, activated partial thromboplastin time, or anti-Xa activity is necessary, because of narrow therapeutic index, to maximize antithrombotic effect and minimize hemorrhagic complications |
Thrombolytics | |||
Tissue plasminogen activator (alteplase) | Binds to fibrin within thrombus, initiating fibrinolysis and converting plasminogen to plasmin | Dogs: Using a 250 mcg/mL injection, 25 mcg/dog, intracamerally in anterior chamber of affected eye, once (total volume must not exceed 0.1 mL) | Monitor for response to treatment and for adverse effects (eg, hyperkalemia); recommended only for hospitalized patients with intensive monitoring and 24-h observation |