OBJECTIVES: Long-term antiplatelet therapy is typically considered standard of care for secondary prevention of cardiac events in acute coronary syndrome (ACS) patients. The European Society of Cardiology consensus treatment guidelines in 2002 support the use of clopidogrel in many of these patients. The goal of this descriptive study was to examine clopidogrel patterns of use in ACS patients in the UK. METHODS: The data source was the IMS Health, Disease Analyzer Mediplus – UK database. This database contains nearly two-million de-identified patient records and 58 million prescriptions continuously collected from approximately 560 participating general practices. The study time period was January 01, 1999 to November 30, 2003. The index ACS event was identified using ICD-10 codes for unstable angina and acute myocardial infarction. Patients were included if they had at least six-months of data both before and after the index ACS event, and at least one prescription for clopidogrel after the event. RESULTS: A total of 9591 patients were included in the ACS cohort and 1110 had at least one clopidogrel prescription (11.6%) and met inclusion criteria. Mean age was 67.1 years; 65.8% were male. Commonly recorded comorbidities included: diabetes, angina, coronary heart disease, and hypertension. Mean length of clopidogrel therapy was 144 days. Patterns of use analysis found 42.5% of patients stopped therapy (defined as not on clopidogrel 28 days prior to end of follow up). A gap in therapy was seen in 82.9% (defined as late refills >14 days apart). Concomitant cardiovascular drug therapies included: ACE inhibitor (34.1%), beta-blocker (12.9%), and statin (51%). CONCLUSIONS: This descriptive study suggests clopidogrel is substantially underutilized in ACS patients. Furthermore, patients had poor long-term adherence to therapy as demonstrated by the number who stopped therapy or had gaps. A large gap exists between current practice and suggested treatment guidelines.