Clopidogrel

Question 1

Mechanism of action?

Answer 1

Clopidogrel is a platelet aggregation inhibitor, it bind irreversibly to ADP receptors Adenosine DiPhosphate P2Y (1,2) subtype found on the surface of platelets. The process is independent with the COX pathway, Clopidogrel’s actions are synergic with Aspirin.

Question 2

Indications?

Answer 2

• acute coronary syndrome, where inhibiting platelet aggregation can prevent/limit arterial thrombosis.
• prevent occlusion in coronary arteries stents.
• long-term secondary prevention of thrombotic arterial events.
• reduce the risk of intra-cardiac thrombus &embolic stroke in AF when Warfarin &oven oral anticoagulants are CIed.

Question 3

Important AE?

Answer 3

• Bleeding, which can be serious if gastrointenstianl, intracranial of post-surgery.
• Gastrointestinal upset : diarrhea, abdominal pain &dyspepsia.
• Rarely thrombocytopenia, since Clopidogrel rarely affects platelet count or its function.

Question 4

Important interactions ?

Answer 4

Clopidogrel is a pro-drug, its combination with cytochrome P450 inhibitors may reduce its critically needed efficacy : Omeprazole, Ciporfloxacine, Erythromycine. some antifungals &some SSRIs. The risk of bleeding is majored when co-prescribed with other anti-platelet drugs or anticoagulants or NSAIDs.

Question 5

How is Clopidogrel taken ?

Answer 5

Orally, its low dose may take a week before manifesting any effects. When rapid effect is necessary, a loading dose of 300mg is introduced, the regular maintenance dose is of 75mg.
When its indication is prevention of thrombosis following a stent operation, it must be continued for 12months with another antiplatelet (dual antiplatelet therapy for 12mnths).

Question 6

Lifetime span of a platelet?

Answer 6

7-10 days. Before surgeries, impose the discontinuation of treatment 7 days prior.