OBJECTIVES: As Comparative Effectiveness Research (CER) gains a stronger foothold in the US Healthcare system we turn our sights on the market implications of conducting “real-world” studies of the effectiveness and safety of a clinical intervention to guide evidence-based practice.  Barriers to assimilation of CER in clinical decision-making may be shaped by market factors such as coverage, reimbursement, and generic availability.  This analysis aims to determine what, if any, changes in prescribing patterns might have been precipitated by the findings of CER studies and examines the possible causes of such changes with respect to differences in efficacy, safety and price. METHODS: We examined prescribing patterns for drugs included in six Comparative Effectiveness Research (CER) studies –one neuroscience, one diabetes and four cardiovascular – before and after publication.  Our analysis separately tracked new and refill prescriptions for the same number of quarterly intervals before and after publication of the studies analyzed, ending with Q2 (June) 2011.  Drug prescription volumes and average wholesale prices (except where noted) were obtained using SDI Health’s Vector One National Audit. Metrics were compared in the quarters before and after study publication.  Statistical significance was defined as p<0.05.  Analyses were performed using Microsoft Excel, two-tailed t-test. RESULTS: Drugs included in three of the six CER studies- neuroscience, diabetes and cardiovascular- showed significant changes in new, refill or total prescriptions of the drugs studies  that were consistent with the published findings (i.e. positive changes following positive findings).  CONCLUSIONS:  Factors, in addition to the studies' findings themselves, that could have contributed to the observations include pricing of the drugs compared in the studies and generic availability.  We hypothesize that factors impacting adoption of CER results in clinical practice include the number of patients enrolled and the method of dissemination of results.