OBJECTIVES: Using recent US national claims data, this study examined characteristics of managed care patients taking clopidogrel in outpatient settings and analyzed patterns of use. METHODS: This retrospective study identified patients with oral antiplatelet claims in a large, national, managed care claims database (Pharmetrics) between 1/2003 – 6/2006 (n=47,364). All medical and pharmacy claims were analyzed during this period. Analysis focused on outpatient use patterns of clopidogrel and patient characteristics, e.g., demographics, comorbidities, inpatient history, and other cardiovascular medication use. Aspirin therapy was not available in the prescription claims data. RESULTS: Clopidogrel was the most widely prescribed antiplatelet, representing 93% of all prescriptions. Men represented 65% of the patients taking clopidogrel. The mean age was 56.9 years, with 69% of individuals aged 50 to 65 years. The most common outpatient diagnoses were essential hypertension (61%), unspecified hyperlipidemia (57%), hypercholesterolemia (44%), and unspecified chest pain (43%). On average, users of clopidogrel had 3.41 prescriptions/month in 2006 at a health plan cost of $376.50/month. Average length of therapy for clopidogrel was 292 days. By patient type, it varied from 283 days for coronary artery bypass surgery, 336 days for percutaneous coronary intervention (PCI), and 344 days for stroke. However, 10.4% of PCI patients took clopidogrel for =30 days. Patients refilled their clopidogrel prescriptions for 93% of the daily regimen needed during therapy. Frequent concomitant cardiac medications included statins (63.9%), beta-blockers (55.0%), ACE-inhibitors (48.7%), and diuretics (14.2%). Data show that 40-50% of patients discontinued another concomitant cardiac medication upon discontinuing clopidogrel. CONCLUSION: Clopidogrel was the dominant oral antiplatelet by market share. These patients also used significant pharmacy resources on other medications. While average duration was largely consistent with treatment guidelines, variations in individual treatment length were detected. This finding suggests inconsistencies in utilization versus treatment guidelines. Early discontinuation of cardiac medications in some patients also raises concern.