Clopidogrel
Clopidogrel is an oral antiplatelet medication used in adults after acute coronary syndrome, percutaneous coronary intervention, ischaemic stroke or peripheral arterial disease. It irreversibly blocks platelet P2Y12 receptors and reduces atherothrombotic events.
- Chemical formula
- C16H16ClNO2S
- CAS number
- 113665-84-2
- ATC code
- B01AC04
- Molecular weight
- 321.82 g/mol
- Drug class
- P2Y12 receptor antagonist (antiplatelet)
- Also known as
- SR-25990, Clopidogrel
What is it?
Clopidogrel is a thienopyridine antiplatelet prodrug approved in 1997. It is supplied as oral tablets and is dispensed only on prescription. The molecule is part of the World Health Organization List of Essential Medicines and is widely used after coronary stent placement and in secondary prevention. Clopidogrel is administered alone or, in many situations, together with low-dose acetylsalicylic acid (dual antiplatelet therapy).
Mechanism of action
Clopidogrel itself is inactive; the active metabolite, formed in the liver by CYP2C19 and other cytochromes, irreversibly binds the P2Y12 ADP receptor on platelets. This blocks ADP-induced amplification of platelet activation and aggregation throughout the platelet's seven to ten-day lifespan. Because the inhibition is irreversible at the receptor level, the antiplatelet effect persists until new platelets are produced, which is relevant for surgery and bleeding management.
Pharmacokinetics
Clopidogrel is rapidly absorbed orally, with the active metabolite reaching peak plasma concentration within one to two hours. Bioavailability is high. The active metabolite has a half-life of approximately 30 minutes, but the antiplatelet effect lasts for the lifespan of the platelet. Hepatic metabolism by CYP2C19 is critical for activation; loss-of-function variants of this enzyme are associated with reduced response. Strong CYP2C19 inhibitors such as omeprazole can also reduce activation.
Indications
Clopidogrel is approved in adults for the prevention of atherothrombotic events after recent acute coronary syndrome, recent ischaemic stroke or established peripheral arterial disease, and in patients with atrial fibrillation when oral anticoagulants are not suitable. According to international guidelines, it is part of dual antiplatelet therapy with acetylsalicylic acid for a defined period after percutaneous coronary intervention. The choice and duration of therapy are made by the prescriber.
Safety profile
The main adverse effect is bleeding, ranging from minor bruising to severe gastrointestinal or intracranial haemorrhage. Combination with other antiplatelets, anticoagulants, NSAIDs or selective serotonin reuptake inhibitors increases the risk. Rare adverse events include thrombotic thrombocytopenic purpura. According to the prescribing information, clopidogrel should be discontinued five days before elective major surgery and used cautiously in active bleeding, severe hepatic impairment and in patients at high risk of falls.
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Frequently asked questions
How long after acute coronary syndrome is clopidogrel needed? ▾
International guidelines typically recommend dual antiplatelet therapy with clopidogrel and acetylsalicylic acid for around twelve months after acute coronary syndrome managed with stenting, with shorter or longer durations in selected cases based on bleeding and thrombotic risk. After this period, single antiplatelet therapy is usually continued long-term. According to the prescribing information, treatment duration is determined individually by the prescriber.
Does the omeprazole interaction matter? ▾
Omeprazole and esomeprazole are strong inhibitors of CYP2C19, the enzyme that activates clopidogrel. Pharmacokinetic studies show reduced active metabolite concentrations and antiplatelet effect when these proton pump inhibitors are co-administered. According to the prescribing information and several regulatory communications, this combination should be avoided when possible; alternative proton pump inhibitors such as pantoprazole are preferred.
What about CYP2C19 genetic testing? ▾
Some patients carry CYP2C19 loss-of-function variants that reduce the activation of clopidogrel and increase the risk of stent thrombosis. Genotype-guided antiplatelet therapy is offered in selected centres, particularly after percutaneous coronary intervention. According to international guidelines, alternatives such as ticagrelor or prasugrel may be preferred in known poor metabolisers; the choice is made by the prescriber on the basis of bleeding risk.
Should clopidogrel be stopped before surgery? ▾
Yes, in many cases. Because clopidogrel irreversibly blocks platelets, the antiplatelet effect persists for several days after the last dose. According to the prescribing information, clopidogrel is usually stopped five days before elective major surgery, with the timing reviewed by the prescribing cardiologist or surgeon. Urgent surgery may require platelet transfusion or specific bleeding-management strategies.
What are the main contraindications for clopidogrel? ▾
Clopidogrel is contraindicated in known hypersensitivity to the molecule and in active pathological bleeding such as peptic ulcer or intracranial haemorrhage. Caution is required in severe hepatic impairment, recent surgery, concomitant anticoagulants and patients at high risk of bleeding. According to the prescribing information, the medical history must be reviewed by a clinician before any prescription, including all concomitant antithrombotic and CYP2C19-active drugs.
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