aspirin and clopidogrel

Both drugs inhibit platelet function by distinct mechanisms, producing additive antiplatelet effects. Aspirin irreversibly inhibits cyclooxygenase-1 (COX-1), reducing thromboxane A2 synthesis, while clopidogrel irreversibly blocks the P2Y12 receptor on platelets, preventing ADP-mediated activation. The combined effect significantly impairs platelet aggregation, increasing the risk of bleeding.

The combination is often used for secondary prevention of thrombotic events, particularly after acute coronary syndrome or coronary stenting. However, it substantially increases the risk of major bleeding, including gastrointestinal bleeding, intracranial haemorrhage, and bleeding from other sites. The benefit of reducing ischaemic events must be weighed against the increased bleeding risk in each patient.

When prescribed for a valid indication, use the lowest effective doses (e.g., aspirin 75-100 mg daily and standard clopidogrel maintenance). Monitor for signs of bleeding, and consider gastroprotective strategies such as a proton pump inhibitor, especially in patients at high risk. Avoid concurrent use of other anticoagulants or antiplatelets without careful assessment. Contraindicated in active pathological bleeding or when the patient has a severe bleeding disorder.

Well-established through clinical trials and guidelines. Dual antiplatelet therapy is standard of care after acute coronary syndrome and percutaneous coronary intervention. The interaction is predictable and widely recognised.