Metformin Toxicity Background - metformin decreases glucose utilization, increases lactate production by hepatocytes - metformin toxicity manifests as lactic acidosis - in absence of acute overdose, rarely develops in patients without comorbidities (e.g., renal/hepatic insufficiency, acute infection) - unclear what minimum dose leads to toxicity
Signs/Symptoms - nausea, abdominal pain, other GI complaints - altered mental status, dyspnea, hypotension, tachycardia
Work-up - BGM - EKG, acetaminophen, salicylate levels to rule out other coningestants - blood gas, BMP, serum lactate - serum metformin levels often do not correlate with severity of poisoning, but negative level rules out toxicity
Management - if acute, GI decontamination with activated charcoal - if hypoglycemic, dextrose 0.5 - 1 g/kg IV, though should seek other causes as metformin itself should not cause hypoglycemia - sodium bicarbonate for severe metabolic acidosis (pH < 7.15) - hemodialysis indications: lactate > 20 mmol/L, pH < 7.0, failure to improve with supportive care within 2 - 4 hours - early consultation with nephrologist and toxicologist
Disposition - patients who appear well and have normal acid-base status after 6 - 8 hours may be medically cleared - asymptomatic patients with persistent acidosis require further observation - symptomatic patients should all be admitted
Resources Metformin Poisoning, UpToDate
