Discontinuation of metformin in the setting of coronary angiography: clinical uncertainty amongst physicians reflecting a poor evidence base.

Aims: Metformin is widely prescribed for the treatment of type 2 diabetes mellitus and is associated with a reduction in diabetes-induced cardiovascular morbidity and mortality. Concerns about metformin-associated lactic acidosis (M-ALA) in patients undergoing contrast-based angiographic procedures have led to the development and publication of a number of guidelines to improve the management of this patient cohort. Methods and results: This review focuses on the evidence behind these guidelines and, in particular, that concerning metformin discontinuation in diabetic patients undergoing coronary angiography and percutaneous intervention. This review addresses and compares guideline-directed management of such patients and includes the results of a UK physician survey to highlight variations in clinical practice. Conclusions: We conclude that evidence for M-ALA in diabetics on metformin undergoing coronary intervention is lacking and existing guidance on the management of such patients is inconsistent. More robust evidence is needed in the form of a large, adequately-sized randomised trial or extensive registry so that we can optimally manage those patients requiring contrast-based coronary interventions who are also taking metformin.