Severe lactic acidosis and hypoglycemia due to acute metformin intoxication in a dog

To report a case of severe lactic acidosis and hypoglycemia due to acute metformin intoxication in a dog.

A female neutered Rat Terrier was presented for an acute onset of seizure-like episodes, weakness, and vomiting approximately 14 hours after ingestion of 198 mg/kg of metformin. The dog was found to be laterally recumbent, paddling, and unresponsive shortly before presentation. On physical exam, the dog was in hypovolemic shock and hypothermic. Blood work revealed severe lactic acidosis and hypoglycemia. The dog was volume resuscitated with intravenous crystalloids and dextrose, followed by a continuous infusion of intravenous fluids and dextrose, as well as administration of isotonic sodium bicarbonate. Repeat blood work showed minimal improvement of the hyperlactatemia for 3 hours despite resolution of hypovolemia and hypoglycemia followed by gradual improvement over the next 9 hours of hospitalization. High performance liquid chromatography/tandem mass spectrometry analysis showed markedly increased plasma metformin concentrations at 3.9 μg/mL. The dog was discharged from the hospital within 24 hours and showed no recurrence of clinical signs one year following discharge.

Metformin-associated lactic acidosis and hypoglycemia is a severe complication in human patients, but has not been reported in veterinary medicine. Aggressive treatment with supportive care including IV fluids and dextrose administration resulted in resolution of the clinical signs in this patient. Metformin toxicosis should be considered in dogs with severe hyperlactatemia and hypoglycemia of unknown etiology.