CAPRIE trial

• phase III study assessing the potential of clopidogrel to prevent ischaemic stroke, MI or vascular death in patients with recent ischaemic stroke, recent MI or peripheral arterial disease (PAD)
  
  
• the trial was randomised and double-blind
  
  
• 19,185 patients randomised to treatment with clopidogrel 75 mg/ day (n=9599) or aspirin 325 mg/ day (n=9586)
  
  
• follow-up was for 1-3 years (mean 1.91 years) equivalent to 36,731 patient-years risk
  
  
• primary endpoint of the CAPRIE trial was an intention to treat analysis of the first occurrence of an event in the outcome cluster of ischaemic stroke, MI or vascular disease
  
  
• there were 939 atherosclerotic events in the clopidogrel group during 17,636 patient-years at risk, an average rate per year of 5.32%. There were 1031 events in the aspirin group during 17,519 patient-years risk, an average rate per year of 5.83%. The relative risk reduction was 8.7% (95% CI 0.3-16.5) in favour of clopidogrel (p=0.043).
• There was no significant differences between aspirin and clopidogrel in relation to the risk of death from any cause
• calculating the number to needed to treat from the CAPRIE trial data, it would be necessary to use clopidogrel instead of aspirin in approximately 200 patients for 1 year to avert one additional major clinical event
• note that clopidogrel was more effective than aspirin for reducing recurrent ischaemic events in patients with recent stroke, recent MI, or peripheral artery disease who had also had previous cardiac surgery (2)

Reference:

1. CAPRIE steering committe (1996). A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). Lancet, 348,1329-1339.
2. Bhatt DL et al (2001). Superiority of clopidogrel versus aspirin in patients with prior cardiac surgery. Circulation, 103, 363-8.