Endocrine Abstracts

Metformin is considered to be the first choice in the treatment of type 2 diabetes mellitus. Lactic acidosis is a rare life-threatening complication of metformin with approximately 50% overall mortality. Metformin is contraindicated in patients with factors predisposing to lactic acidosis such as impaired renal function (eGFR <30 mL/min). Herein, we present a hemodialysis patient who developed lactic acidosis after inadvertent usage of metformin.

Case report: A 77-year-old woman was admitted to the emergency department with complaints of nausea, vomiting, black stools, weakness and deterioration in general condition. The patient underwent regular hemodialysis twice a week for 1.5 years due to hypertension and end-stage kidney disease. She was anuric for one year. The last dialysis session was performed 3 days ago. Her family said she had inadvertently received six metformin tablets resembling calcium acetate pills, three in the morning and three in the evening, two days ago. Metformin belonged to one of the family members. She was afebrile, tachypneic, agitated and confused. Heart rate was 145 b/min, blood pressure 70/30 mmHg and oxygen saturation in the room air 75%. There was no significant cardiovascular and pulmonary findings. Laboratory tests showed glucose 88 mg/dl, urea 199 mg/dl, creatinine 10.1 mg/dl, sodium 134 mmol/l, potassium 6.3 mmol/l, white blood cell 42.7 K/mm³ and hemoglobin 10.5 g/dL. Her liver function tests were normal. Wide-anion gap metabolic acidosis without ketonemia was detected. The pH was 6.9, bicarbonate (HCO₃^-) 6 mmol/L, and lactate 140 mmol/L. Metformin-induced lactic acidosis was diagnosed. She was treated with positive inotropic support and bicarbonate infusion. Hemodialysis with bicarbonate buffered replacement fluid was started to remove metformin and correct lactic acidosis. After dialysis, control blood gas values were mildly improved (pH 7.16, lactate 108 mg/dL and HCO₃^- 13.8 mmol/L). Then, despite the dialysis treatment, acidosis deepened (pH 6.8, HCO₃^- 6 mmol/L and lactate 170 mg/dL) and she died with sudden cardiac arrest.

Conclusion: Lactic acidosis and/or hypoglycemia have been reported after inadvertent metformin overdose in diabetic hemodialysis patients. Our case was the first non-diabetic patient who developed lactic acidosis after accidentally metformin use. Significant lactic acidosis occurs only in the presence of comorbid conditions including kidney failure. Drug use should be controlled in elderly dialysis patients.