Persistence, adherence and outcomes with antiplatelet regimens following cerebral infarction in the Tayside Stroke Cohort

Background: Co-prescribed aspirin and dipyridamole are more effective than aspirin alone following cerebral infarction; however, patients may struggle with this more complex regimen. The objectives of this study were: (1) to describe postdischarge prescribing of antiplatelet regimens, (2) to measure patient persistence with different antiplatelet regimens, and (3) to measure whether persistence impacts on outcomes. Methods: We used record linkage of the Tayside Stroke Cohort with community dispensed prescribing data from 1994 to 2005. All patients had suffered a radiologically confirmed cerebral infarction and were excluded if they had previously used or had other indications for antiplatelet agents. We measured persistence to initial and any antiplatelet regimen using survival analysis. To assess the impact of therapy we used survival analysis to follow up until the APTC endpoint of serious vascular event (myocardial infarction, stroke or vascular death) or censored. Antiplatelet regimen was entered as a time-dependent covariate in a Cox model that also adjusted for age, sex, history of diabetes and baseline use of nitrates and statins. Results: The study cohort contained 1,407 stroke patients (mean age 70.3 years, 46.8% male), with a total follow-up of 4,243 patient-years. Patients initiated on aspirin with dipyridamole had a worse persistence to their initial regimen compared with those initiated on aspirin alone (hazard ratio for non-persistence 1.62; 95% CI 1.37-1.92), but better persistence with any antiplatelet medication long term (hazard ratio 0.86; 95% CI 0.73-1.02). Compared to aspirin monotherapy, receiving no antiplatelet therapy was associated with significantly worse patient outcomes (hazard ratio 1.50; 95% CI 1.21-1.87), whilst receiving prescribed aspirin with dipyridamole was associated with better outcomes (hazard ratio 0.75; 95% CI 0.56-0.99). Only a few patients received clopidogrel or other antiplatelet regimens. Conclusions: Patients discharged on dual therapy have worse adherence to their initial regimen but better persistence to any antiplatelet agents in the long term. Continued exposure to antiplatelet regimens predicts good outcomes in patients with cerebral infarction