Metformin-induced lactic acidosis: report of a case

Lactic acidosis associated with diabetic patients receiving metformin therapy is rare but may cause significant morbidity and mortality. In nearly all reported cases of metformin-associated lactic acidosis, contraindications to its use were noted, especially renal insufficiency. We describe a 59-year-old diabetic man treated with metformin for more than three years. During the third year of use, he experienced progressive renal function impairment, and during the final month of use, he became azotemic. He was maintained on continuous ambulatory peritoneal dialysis. Several days prior to admission, he suffered from epigastralgia, nausea and vomiting, followed by progressive dyspnea which was Kussmaul in nature. Profound hypotension developed and he sank progressively into a coma. Wide-anion gap metabolic acidosis without ketonemia was detected. His blood lactate level was elevated and metformin-induced lactic acidosis was substantiated. An elevated plasma metformin level of greater than 50 mg/mL was determined later by high-performance chromatography. Rigorous treatment including bicarbonate therapy, bicarbonate hemodialysis and vasoactive agents as well as supportive measures were provided. With a return of pH to normal, the hypotension resolved and his consciousness level slowly improved. Our patient survived this disastrous event, but some neurologic sequelae remained. In order to avoid this life-threatening metabolic disturbance, patients with any contraindications should not be prescribed metformin.