Clopidogrel versus aspirin for secondary prophylaxis of vascular events: a cost-effectiveness analysis.

PURPOSE Clopidogrel is more effective than aspirin in preventing recurrent vascular events, but concerns about its cost-effectiveness have limited its use. We evaluated the cost-effectiveness of clopidogrel and aspirin as secondary prevention in patients with a prior myocardial infarction, a prior stroke, or peripheral arterial disease. METHODS We constructed Markov models assuming a societal perspective, and based analyses on the lifetime treatment of a 63-year-old patient facing event probabilities derived from the Clopidogrel versus Aspirin in Patients at Risk of Ischemic Events (CAPRIE) trial as the base case. Outcome measures included costs, life expectancy in quality-adjusted life-years (QALYs), incremental cost-effectiveness ratios, and events averted. RESULTS In patients with peripheral arterial disease, clopidogrel increased life expectancy by 0.55 QALYs at an incremental cost-effectiveness ratio of $25,100 per QALY, as compared with aspirin. In poststroke patients, clopidogrel increased life expectancy by 0.17 QALYs at a cost of $31,200 per QALY. Aspirin was both less expensive and more effective than clopidogrel in post-myocardial infarction patients. In probabilistic sensitivity analyses, our evaluation for patients with peripheral vascular disease was robust. Evaluations of stroke and myocardial infarction patients were sensitive predominantly to the cost and efficacy of clopidogrel, with aspirin therapy more effective and less expensive in 153 of 1000 simulations (15.3%) in poststroke patients and clopidogrel more effective in 119 of 1000 simulations (11.9%) in the myocardial infarction sample. CONCLUSION Clopidogrel provides a substantial increase in quality-adjusted life expectancy at a cost that is within traditional societal limits for patients with either peripheral arterial disease or a recent stroke. Current evidence does not support increased efficacy with clopidogrel relative to aspirin in patients following myocardial infarction.