Metformin toxicity: a report of 204 cases from Iran.

Objective: The aim of this study was to evaluate the frequency of metformin-associated lactic acidosis in our metformin-intoxicated patients, the general approach for their management, and determine the frequency of hypoglycemia and outcome in these patients. We also wanted to see if there was a significant difference in the course and outcome of metformin poisoning between our patients and those reported in the literature.

Materials And Methods: Files of all patients diagnosed with metformin toxicity were retrospectively evaluated. A purposemade questionnaire containing the patients' demographic data, vital signs and lab tests on presentation, time of development of hypoglycemia and metabolic acidosis (if any), treatment modalities performed for the patients and their indications, and the patients' outcomes was filled. The patients were evaluated in total and then assigned into two groups of metformin alone (group 1) and multi-drug toxicity including metformin (group 2) and were compared.

Results: A total of 204 patients were reviewed. Fifty-five (26.9%) were in group 1 and 149 (73.1%) were in group 2. Sixteen and 52 patients in groups 1 and 2 had acidosis. Dialysis was performed in only four patients, all of whom belonged to group 1 (P = 0.005). They were all dialyzed only once. Two patients (1%) died both of whom were in group 2. Groups 1 and 2 were insignificantly different in all characteristics except for their aspartate transaminase and creatine phosphokinase. Almost 23% of the patients in group 1 had experienced hypoglycemia sometime during their course of hospitalization.

Conclusions: Although lactic acidosis is considered to be a serious condition resulting in high mortality and morbidity rates, it seems that our patients can easily and safely be managed with conservative therapies. Most of them do not need aggressive treatments including hemodialysis. Metformin seems to cause hypoglycemia more than what was previously considered.