SUN-683 Was Metformin the Culprit for This Lactic Acidosis?

Metformin is the first-line drug for treatment of Type 2 diabetes. A meta-analysis of 70,490 patient-years of metformin use reported no lactic acidosis. We present a case of a patient who developed lactic acidosis while on Metformin; with other contributing factors. Case Description A 72-year old male with dementia, diabetes, hypertension, hypothyroidism and “muscular dystrophy” was admitted with encephalopathy. Medications included levothyroxine, donepezil, insulin glargine and metformin. A Brain CT scan revealed frontal lobe atrophy and lacunar infarcts. Admission blood work revealed lactic acidosis of 5.6. Sepsis workup was negative. Metformin was discontinued, and the patient improved with intravenous hydration. Upon discharge, Metformin was restarted. Follow-up lactic acid was normal. After a subsequent hospitalization with similar presentation and peak lactic acid of 4.7, metformin was stopped altogether. The patient was referred to a neuromuscular specialist and a diagnosis of Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) was made. The “muscular dystrophy” was likely mitochondrial disease. A third hospitalization (while not on Metformin) saw a peak lactic acid of 2.8. We concluded that the lactic acidosis was secondary to MELAS, but Metformin had caused the significant spikes seen during the first two hospitalizations. Discussion Mitochondrial disorders must be in the differential diagnosis for patients diagnosed with muscular dystrophy. The hallmark of MELAS syndrome is stroke-like episodes that result in hemiparesis, hemianopia, or cortical blindness. Other features include seizures, recurrent headaches, vomiting, short stature, and muscle weakness. Patients with mitochondrial diseases also have a high incidence of diabetes. Lactic acidosis occurs during stress. DNA testing is the gold standard for diagnosis. Conclusion Metformin is contraindicated in patients with mitochondrial disease and diabetes due to the predisposition for lactic acidosis. This is not part of the current package inserts for prescribers and patients- and we strongly recommend inclusion of this language.