Cost-effectiveness of New Antiplatelet Regimens Used as Secondary Prevention of Stroke or Transient Ischemic Attack

BACKGROUND: Compared with aspirin alone, use of the new antiplatelet regimens, including aspirin combined with dipyridamole and clopidogrel bisulfate, has been found to further reduce the risk of stroke and other vascular events in patients who have experienced stroke or transient ischemic attack. However, their cost-effectiveness ratios relative to aspirin alone have not been estimated. METHODS: We developed a Markov model to measure the clinical benefits and the economic consequences of the following strategies to treat high-risk patients aged 65 years or older: (1) aspirin, 325 mg/d; (2) aspirin, 50 mg/d, and dipyridamole, 400 mg/d; and (3) clopidogrel bisulfate, 75 mg/d. Input data were obtained by literature review. Outcomes were expressed as US dollars per quality-adjusted life-year (QALY). RESULTS: The use of aspirin combined with dipyridamole was more effective and less costly compared with the use of aspirin alone, providing a gain of 0.3 QALY for a 65-year-old patient. This regimen remained cost-effective despite wide sensitivity analyses. Clopidogrel was more effective and more costly compared with aspirin alone, yielding a gain of 0.2 QALY with a marginal cost-effectiveness ratio of $26,580 per each additional QALY (patient aged 65 years). Sensitivity analyses demonstrated that the efficacy of clopidogrel and its cost were key factors in determining its cost-effectiveness ratio compared with aspirin, which exceeded $50,000 when its efficacy decreased by half or its cost doubled. CONCLUSION: To prevent stroke in high-risk patients, dipyridamole combined with aspirin was more effective and less costly than aspirin alone, and clopidogrel was cost-effective compared with current standards of medical practice, except in extreme scenarios.