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Ketchum K, Peterson K, Thakurta S, et al. Drug Class Review: Newer Antiplatelet Agents: Final Update 2 Report [Internet]. Portland (OR): Oregon Health & Science University; 2011 Jun.

Cover of Drug Class Review: Newer Antiplatelet Agents

Drug Class Review: Newer Antiplatelet Agents: Final Update 2 Report [Internet].

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Summary

Strength of Evidence

The results of this review are summarized in Table 9, below, and Appendix F summarizes the strength of the evidence for each key question. High-strength, comparative evidence was found only for effectiveness outcomes for the comparison of prasugrel and clopidogrel following coronary revascularization and for the comparison of the fixed-dose combination of extended-release dipyridamole plus aspirin and clopidogrel following recent stroke or transient ischemic attack. Evidence of the direct comparison between ticlopidine and clopidogrel was available in patients undergoing coronary interventions and following a recent stroke or transient ischemic attack, but was generally of moderate to low strength. No direct comparative data was available in patients with acute coronary syndromes or peripheral vascular disease. For evaluation of differences based on duration of therapy, evidence was generally moderate strength but limited to the question of whether 6 to 12 months of clopidogrel treatment was better than 1 month following coronary interventions. For subgroups based on age, race, and sex, evidence was generally low strength and came primarily from subgroup analyses of the primary composite effectiveness outcomes from head-to-head trials of prasugrel and clopidogrel following coronary revascularization and of the fixed-dose combination of extended-release dipyridamole plus aspirin and clopidogrel following recent stroke or transient ischemic attack. For evaluation of concomitant use of proton pump inhibitors in patients taking clopidogrel, evidence came primarily from observational studies. However, as observational studies were included in our review only to evaluate harms and not effectiveness outcomes, these studies only provided low- to moderate-strength evidence for evaluation of gastrointestinal bleeding risk and insufficient evidence to draw conclusions about risk of cardiovascular events.

Table 9. Summary of the evidence.

Table 9

Summary of the evidence.

Limitations of this Report

As with other types of research, the limitations of this systematic review are important to recognize. These can be divided into 2 groups, those relating to generalizability of the results and those relating to methodology within the scope of this review. The generalizability of the results were limited by the scope of the key questions, inclusion criteria, and by the generalizability of the studies included. Most studies included narrowly defined populations of patients who met strict criteria for case definition, had fewer comorbidities, and used fewer concomitant medications. Minorities, female patients, and the most seriously ill patients were under represented.

Methodological limitations of the review within the defined scope included the exclusion of studies published in languages other than English and lack of a specific search for unpublished studies. Few direct head-to-head comparisons of the included drugs have been conducted for acute coronary syndrome and peripheral arterial disease, which limits our conclusions to indirect comparison of placebo-controlled trials for many of the outcomes. This limits the strength of the evidence due to heterogeneity of trial populations, interventions, and outcomes assessment.

Applicability

One potential limitation to the applicability of the findings of this review is that they relate to a narrower range of drugs than are available in clinical practice. The selection of drugs included in this review was influenced by the specific programmatic interests of the organizations participating in the Drug Effectiveness Review Project and are not meant to be read as a usage guideline. Of the drugs studied, trials differed with respect to dosing regimens limiting any conclusions about optimal dose.

Studies Pending Review

We identified no trials in progress that would meet inclusion criteria for this review and would potentially change conclusions.

Copyright © 2011 by Oregon Health & Science University.
Bookshelf ID: NBK61804

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