OBJECTIVES: The goal of this study is to evaluate patient persistence and adherence rates to HMG-CoA reductase inhibitors (statins) in a managed care setting. METHODS: Retrospective claims analysis of a nationwide managed care pharmacy database was conducted for continuously benefit-eligible patients who were initiated on statin therapy from 1999 to 2002. Patients were tracked for 12 months starting from the date of initial therapy. Persistence (remaining on therapy at 12 months after therapy initiation), mean medication possession ratio (MPR) over 12 months, and adherence (adherent to statin defined as MPR = 0.8) were assessed. RESULTS: Among the 281,564 patients selected, 159,833 (56.8%) started on atorvastatin, 66,526 (23.6%) on simvastatin, 27,187 (9.7%) on pravastatin, 20,921 (7.4%) on fluvastatin, and 7,097 (2.5%) on lovastatin. The mean age was 61.3+/-13.2 years and 51% were male. The persistence at 12 months, mean MPR over 12 months, and adherence rate for all statins was 52.5%, 68.7%, 52.6%, respectively. The persistence rate at 12 months for patients initiated on atorvastatin, simvastatin, fluvastatin, pravastatin, and lovastatin was 54.1%, 53.7%, 49.7%, 44.8%, 41.0%, respectively (p <0.0001 for all comparisons except for atorvastatin vs. simavastatin). The mean MPR for patients initiated on atorvastatin, simvastatin, fluvastatin, pravastatin, and lovastatin was 70.1%, 68.3%, 65.2%, 65.1%, and 62.2%, respectively (p <0.0001 for all comparisons except for fluvastatin vs. pravastatin). Adherence for patients initiated atorvastatin, simvastatin, pravastatin, fluvastatin, and lovastatin was 54.1%, 52.6%, 48.4%, 47.7%, and 47.2% respectively (p <0.0001 for all comparisons except for pravastatin vs. fluvastatin, pravastatin vs. lovastatin, and fluvastatin vs. lovastatin). CONCLUSIONS: In general, patients initiated on atorvastatin are most favorable in terms of persistence, medication possession ratio, and adherence rates, followed by simvastatin, fluvastatin, pravastatin, and lovastatin patients. While there are statistical significant differences between the agents, additional studies are needed to determine if this translates to clinical differences.