title: Persistence, adherence and outcomes with antiplatelet regimens following cerebral infarction in the Tayside Stroke Cohort.
abstract: 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.
authors.affiliation: Medicines Monitoring Unit, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK. rob@memo.dundee.ac.uk
authors.forename: Robert W V
authors.initials: RW
authors.lastname: Flynn
authors.forename: Thomas M
authors.initials: TM
authors.lastname: MacDonald
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Murray
authors.forename: Ronald S
authors.initials: RS
authors.lastname: MacWalter
authors.forename: Alexander S F
authors.initials: AS
authors.lastname: Doney
mesh_terms: D000368:Aged; D001241:Aspirin / Q000627:therapeutic use; D002544:Cerebral Infarction / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000401:mortality; D000077144:Clopidogrel; D015331:Cohort Studies; D004176:Dipyridamole / Q000627:therapeutic use; D011307:Drug Prescriptions; D004359:Drug Therapy, Combination; D004363:Drug Utilization; D005260:Female; D006801:Humans; D008297:Male; D008498:Medical Record Linkage; D016347:Medical Records Systems, Computerized; D055118:Medication Adherence; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data; D016016:Proportional Hazards Models; D011859:Radiography; D018570:Risk Assessment; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology; D016019:Survival Analysis; D013988:Ticlopidine / Q000031:analogs & derivatives / Q000627:therapeutic use; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D004176:Dipyridamole; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin