5 Switching aspirin to other antiplatelet medications (e.g. ticlopidine, clopidogrel, and so on) is a reasonable alternative in the treatment of patients who cannot tolerate aspirin due to dyspepsia or allergy, or who have gastrointestinal complications from aspirin, but there are significant drawbacks with all existing antiplatelet agents. For example, ticlopidine

is associated with neutropenia in 2.1% of patients.6 Clopidogrel is associated with an increased risk of upper gastrointestinal bleeding (9–13% by 1 year) in patients with prior histories of peptic ulcer diseases.7 Clinicians should therefore balance the CV benefits and GI or hematological risks when prescribing antiplatelet agents. Currently, two categories of antiplatelet agents, aspirin and the thienopyridines (ticlopidine, clopidogrel and prasugrel) are popular for the primary or secondary prevention of cardiovascular Ibrutinib molecular weight Silmitasertib chemical structure diseases. Aspirin reduces platelet activity by decreasing thromboxane synthesis through the inhibition of cyclooxygenase (COX)-1 enzymes. However, due to its inhibition

of COX-mediated prostaglandin synthesis, direct cytotoxicity and microvascular injury, aspirin is associated with upper GI side effects, which range from mild dyspepsia (31%) to life-threatening bleeding and perforation from peptic ulcers (3%) over a period of 4 years in the UK Transient Ischaemic Attack Study.8 A prospective study by Laine

et al. reported that the 12-week cumulative incidence of ulcers in low-dose aspirin users was 7%.9 The risk of serious ulcer complications are about two- to fourfold higher in patients taking low-dose (75–325 mg daily) aspirin than control.10 Clopidogrel is a thienopyridine derivative, which inhibits platelet function by selectively Metalloexopeptidase and irreversibly blocking the adenosine diphosphate (ADP) receptor on platelets, thereby affecting ADP-dependent activation of the GpIIb-IIIa complex, the major receptors for fibrinogen present on the platelet surface.11 The CAPRIE (Clopidogrel vs Aspirin in Patients at Risk of Ischemic Events) study showed that long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischemic events.12 Additionally, clopidogrel induced fewer episodes of GI bleeding than aspirin. However, a recent study from our center demonstrated that 11% of the patients with a peptic ulcer history who took clopidogrel for the prevention of ischemic events had recurrent peptic ulcer during a 6-month follow-up period.13 Another prospective study also showed 9% of patients with a history of peptic ulcer bleeding who took clopidogrel had recurrent ulcer bleeding within one year.7 The mechanisms leading to recurrent peptic ulcers and ulcer bleeding among patients receiving clopidogrel are unclear.