Clopidogrel

Clopidogrel is a thienopyridine antiplatelet drug used to reduce platelet-mediated thrombus formation. Its major veterinary application is prevention of cardiogenic arterial thromboembolism in cats, particularly recurrence after a previous event. It is also used in selected dogs with a high thrombotic risk as part of an individualized antithrombotic plan.

Group

Antiplatelet prodrug

Mechanism of Action

Clopidogrel undergoes hepatic conversion to an active metabolite that irreversibly inhibits the platelet P2Y12 ADP receptor. This prevents ADP-mediated amplification of platelet activation and reduces activation of the glycoprotein IIb/IIIa complex required for fibrinogen-mediated platelet aggregation. The affected platelet remains inhibited for the remainder of its lifespan, reducing formation of platelet-rich thrombi.

Dose Rates

Cats

Use / stage	Dose	Route	Schedule	Instructions
Arterial thromboembolism prevention	18.75 mg/animal	PO	Every 24 h	Equivalent to one quarter of a 75 mg tablet; this mathematical fraction is not a verified equal-division instruction.
Platelet inhibition	1–3 mg/kg	PO	Every 24 h	Historical weight-based alternative; the established fixed 18.75 mg-per-cat regimen remains separate.
Platelet inhibition with aspirin	Reference only	PO		Clopidogrel 0.5–1 mg/kg orally daily is a lower-dose alternative when combined with aspirin; the complete aspirin plan and bleeding risk must be assessed separately.
Historical fixed-dose aspirin combination	Reference only	PO		Clopidogrel 7 mg per cat orally daily with aspirin 40–81 mg per cat every three days was proposed, but the source calls for clinical trials. It is not a routine substitute for clopidogrel monotherapy.

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Platelet inhibition — Maintenance	2 mg/kg	PO	Every 24 h
Platelet inhibition — Loading	2–4 mg/kg	PO	Once
Platelet inhibition — Maintenance	1–2 mg/kg	PO	Every 24 h
Higher-dose platelet inhibition loading — Loading	10 mg/kg	PO	Once	Higher alternative loading dose reported in some cases; not the routine starting choice.
Platelet inhibition	1–3 mg/kg	PO	Every 24 h
Platelet inhibition with aspirin	Reference only	PO		Clopidogrel 0.5–1 mg/kg orally daily is a lower-dose alternative when combined with aspirin; the complete aspirin plan and bleeding risk must be assessed separately.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Platelet inhibition — Loading	4 mg/kg	PO	Once
Platelet inhibition — Maintenance	2 mg/kg	PO	Every 24 h

Indications

Prevention of recurrent cardiogenic arterial thromboembolism in cats after an initial thromboembolic event.
Thromboprophylaxis in cats with cardiomyopathy and high-risk features such as marked left atrial enlargement, spontaneous echocardiographic contrast or intracardiac thrombus.
Antiplatelet thromboprophylaxis in selected dogs with disorders associated with increased thrombotic risk, including some immune-mediated or protein-losing diseases.

Contraindications

High bleeding risk or active bleeding.
Discontinue sufficiently before planned surgery according to the clinical situation.

Interactions

Anticoagulants and other antiplatelet medicines increase bleeding risk.
Omeprazole inhibits activation in people, but this interaction has not been demonstrated in dogs; feline and equine clinical effects are uncertain.
NSAIDs increase bleeding risk; phenytoin and torsemide metabolism may be affected.

Adverse effects

Bleeding
Bitter taste and oral refusal

Preparations

Preparation	Form	Strength	Route
Clopidogrel 75 mg tablet	Tablet	75 mg / tablet	PO
Compounded clopidogrel oral suspension 5 mg/mL Four 75 mg tablets in Ora-Plus/Ora-Sweet to final 60 mL; reported 60-day potency at 5°C or 25°C protected from light.	Oral Liquid	5 mg / mL	PO

Monitoring and Administration

Monitor bleeding and thrombotic risk. Some animals do not respond adequately.

Aspirin coadministration is often unnecessary. Platelet effects persist after drug withdrawal.

Feline tablet fragments can be placed in a gelatin capsule to reduce bitterness.