Platelet aggregation inhibitors in primary and secondary prevention of ischemic stroke

The ischaemic stroke (IS) is one of the most frequent cause of death in Germany. Besides of non-drug many drug-based interventions are used in primary or secondary prevention of IS, among them the thrombocyte aggregation inhibitors (TAI).

The evaluation addresses the questions on medical efficacy and cost-effectiveness of the TAI administration in the prevention of IS as compared to the management of risk factors alone as well as to the use of anticoagulant drugs.

The literature search for articles published after 1997 was conducted in December 2003 in the most important medical and economic databases. The medical analysis was performed on the basis of the most up-to date meta-analyses of randomised controlled trials (RCT) as well as of new published RCT. The data from the studies for stroke, bleeding complications as well as for the combined endpoint "severe vascular events" (SVE: death or stroke or myocardial infarction) were summarised in meta-analyses. In order to include grey literature contact has been taken up with the pharmaceutical manufacturers of TAI. Results are presented in a descriptive way.

The medical analysis included data from 184 RCT (vs. placebo) and from 22 RCT (vs. anticoagulant drugs). The absolute reduction of IS (4.8% vs. 6.6%; p<0,00001) and SVE (10.0% vs. 12.4%; p<0,00001) were definitely higher than the absolute increase of bleeding complications (1.6% vs. 0.9%; p<0,00001), but relatively similar to this absolute increase in a subpopulation with a low risk for SVE. With regard to the stroke prevention, evidence of efficacy could be yielded for acetylsalicil acid (ASA), dipyridamole, cilostazol, ridogrel and the combination ASA with dipyridamole. ASA is less effective than anticoagulants in the prevention of ischaemic stroke in atrial fibrillation, however, it causes fewer bleeding complications. Low dosed ASA can be considered cost-effective in secondary prevention of ischemic stroke, which is not the case for clopridogrel. Dipyridamole/ASA being more effective compared with ASA alone is connected with higher acquisition costs.

The exclusive consideration of stroke prevention is limited, as well as physicians by allocation to TAI expect to avoid all thrombotic events. Since no pharmacoeconomic studies exist for the German context, the economic assessment had to be based on international evidence.

From the medical point of view, TAI may be recommended for primary and secondary prevention of IS in patients with a high risk of severe vascular events and with low risk for bleeding complications. ASA may be also administered in patients with atrial fibrillation in case of contraindication to anticoagulation drugs. From the health economic point of view a systematic primary prophylaxis of IS with ASA cannot be recommended, whereas in secondary prophylaxis savings can be made. Neither the use of Dipyridamole/ASS nor Clopidogrel is advisable for a systematic secondary prophylaxis of IS.