Clopidogrel and modified-release dipyridamole for the prevention of occlusive vascular events (review of Technology Appraisal No. 90): a systematic review and economic analysis.

BACKGROUND: Occlusive vascular events such as myocardial infarction (MI), ischaemic stroke and transient ischaemic attack (TIA) are the result of a reduction in blood flow associated with an artery becoming narrow or blocked through atherosclerosis and atherothrombosis. Peripheral arterial disease is the result of narrowing of the arteries that supply blood to the muscles and other tissues, usually in the lower extremities. The primary objective in the treatment of all patients with a history of occlusive vascular events and peripheral arterial disease is to prevent the occurrence of new occlusive vascular events.

OBJECTIVES: To assess the clinical effectiveness and cost-effectiveness of clopidogrel and modified-release dipyridamole (MRD) alone or with aspirin (ASA) compared with ASA (and each other where appropriate) in the prevention of occlusive vascular events in patients with a history of MI, ischaemic stroke/TIA or established peripheral arterial disease. To consider the clinical effectiveness and cost-effectiveness of clopidogrel in patients with multivascular disease. This review is an update of the evidence base for the National Institute for Health and Clinical Excellence (NICE) guidance Technology Appraisal No. 90 (TA90) entitled Clopidogrel and modified-release dipyridamole for the prevention of occlusive vascular events (2005).

DATA SOURCES: Four electronic databases (EMBASE, MEDLINE, Web of Science and The Cochrane Library) were searched for randomised controlled trials (RCTs) and economic evaluations. Submissions to NICE by the manufacturers of the interventions were also considered.

REVIEW METHODS: A systematic review of clinical effectiveness and cost-effectiveness was conducted. To manage heterogeneity between trials, indirect analysis (using a mixed-treatment methodology) was performed on selected clinical outcomes. A new economic model was developed to assess incremental costs per life-year gained [quality-adjusted life-years (QALYs)].

RESULTS: For evidence of clinical effectiveness, four RCTs were identified: CAPRIE (Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events), ESPRIT (European/Australasian Stroke Prevention in Reversible Ischaemia Trial), PRoFESS (Prevention Regimen For Effectively avoiding Second Strokes) and ESPS-2 (Second European Stroke Prevention Study). In CAPRIE (patients with MI, ischaemic stroke or peripheral arterial disease), statistically significant outcomes in favour of clopidogrel were noted for the primary outcome (first occurrence of ischaemic stroke, MI or vascular death) compared with ASA [relative risk reduction 8.7%; 95% confidence interval (CI) 0.3% to 16.5%; p = 0.043]. In ESPRIT (patients with ischaemic stroke/TIA) for the primary outcome (first occurrence of death from all vascular causes, non-fatal stroke, non-fatal MI or major bleeding complication), the risk of event occurrence was statistically significantly lower in the MRD + ASA arm than in the ASA arm [hazard ratio (HR) 0.80; 95% CI 0.66 to 0.98], with no statistically significant difference in bleeding events between the two arms. In PRoFESS (patients with ischaemic stroke) the rate of recurrent stroke of any type (primary outcome) was similar in the MRD + ASA and clopidogrel groups, and the null hypothesis (that MRD + ASA was inferior to clopidogrel) could not be rejected. In ESPS-2 (patients with ischaemic stroke/TIA), on the primary outcome of stroke, statistically significant differences in favour of MRD + ASA were observed compared with ASA and MRD alone (relative risk 0.76; 95% CI 0.63 to 0.93). The outcomes addressed in the mixed-treatment comparisons (limited by the available data) for the ischaemic stroke/TIA population confirmed the results of the direct comparisons. The 11 economic evaluations included in the review of cost-effectiveness indicated that for patients with previous peripheral arterial disease, ischaemic stroke or MI, clopidogrel is cost-effective compared with ASA, and for patients with previous ischaemic stroke/TIA, treatment with MRD + ASA is cost-effective compared with any other treatment in patients in the secondary prevention of occlusive vascular events. The relevance of the review was limited as the economic evaluations were not based on the most current clinical data. Cost-effectiveness results generated from the Assessment Group's de novo economic model suggested that the most cost-effective approach for patients with ischaemic stroke/TIA is clopidogrel followed by MRD + ASA then ASA. For patients with MI, the most cost-effective approach is ASA followed by clopidogrel. For patients with established peripheral arterial disease, the most cost-effective approach is clopidogrel followed by ASA. For patients with multivascular disease, clopidogrel followed by ASA is the most cost-effective approach. Incremental cost-effectiveness ratios (ICERs) were also calculated for patients who are intolerant to ASA. Assuming that the branded price for clopidogrel is used and TA90 guidance is not applied, all of the ICERs range between £2189 and £13,558 per QALY gained. Probabilistic sensitivity analyses were fully consistent with these findings.

CONCLUSIONS: The evidence suggests that the most cost-effective treatment for patients with ischaemic stroke/TIA is clopidogrel followed by MRD + ASA followed by ASA; for patients with MI, ASA followed by clopidogrel; and for patients with established peripheral arterial disease or multivascular disease, clopidogrel followed by ASA.

FUNDING: The National Institute for Health Research Health Technology Assessment programme.