Metformin Intolerance: A Proposal for Definition Using the GSRS

Abstract

Metformin is a first line drug for the treatment of patients with type 2 diabetes mellitus (T2DM) and has been associated with metformin intolerance with disappointing patient adherence. Since there is no official definition for metformin intolerance, comparison of international study results on gastrointestinal complaints is almost impossible. In the present study with type 2 diabetes patients who are on a metformin immediate-release (MIR) and are visiting the outpatient’s department of internal medicine. To create a quantifiable and standardized definition of metformin intolerance, this study used the Gastro-intestinal Symptom Rating Scale (GSRS) to evaluate the gastrointestinal complaints. A total of 59 patients (mean age 62.56; +/- 12.08) completed the GSRS in an interview with a skilled investigator. The mean GSRS score for the study population was 34.56 (+/- 14.57). Subsequently two subpopulations were created using 50 as a cutoff point. This resulted in two populations with statistically significant different GSRS scores of 55.50 (+/- 7.88) for patients with a GSRS score of ≥ 50 versus 28.04 (+/- 8.86) for patients with a GSRS score of < 50. The total GSRS results for the various metformin dosages yielded comparable results (figure 1, p<0.05). The authors recommend the use of the GSRS in all studies on the topic of metformin intolerance to enable the comparison of results of international studies. In addition, the authors propose the use of a cutoff GSRS score of 50 as an international definition for metformin intolerance.