Provider Decisions and Patient Outcomes After Premature Metformin Discontinuation

The purpose of this study was to evaluate the effects of alternative antihyperglycemic therapy after discontinuation of metformin due to documented declining renal function. This retrospective, single-site study evaluated patients who had metformin discontinued between 1 January 1999 and 30 September 2013. Medical records were evaluated for documented adverse events, subsequent glycemic control, and costs associated with the alternative therapy. Patients served as their own controls. A total of 179 patients met study entry criteria, and their peak A1C was significantly higher within the year after metformin discontinuation (P <0.001). After the provider added new medications to control patients' blood glucose, their A1C by the end of the first year after discontinuing metformin was similar to their A1C while taking metformin. Significant weight gain accompanied the use of the medications added to replace metformin, with an average increase of 3.81 kg (P <0.001). Additionally, after discontinuing metformin, more patients experienced hypoglycemia with the addition of other medications to control their blood glucose (P <0.001). As expected, the cost of therapy was significantly higher (P <0.0001) after metformin was discontinued because metformin was generically available, whereas the replacement medications frequently were not. Providers should consider the expanded recommendations for the use of metformin in patients with mild to moderate stable renal dysfunction to help such patients avoid weight gain, hypoglycemia, loss of blood glucose control, and increased costs.