Crowley MJ, et al. - This study explored the potential moderating impact of prevalent metformin use on the cardiovascular effects of dipeptidyl peptidase 4 inhibitors (DPP-4i). Findings demonstrated that baseline metformin status may have a moderating effect on cardiovascular outcomes with DPP-4i use. In addition, there was residual uncertainty as to how DPP-4i impact cardiovascular outcomes, based on concurrently prescribed medications.