A Rare Effect of a Common Drug: a case report

Sara Silva Ribeiro, Maria Fortunas Teixeira, Maria Teresa Nunes

Keywords: diabetes mellitus; oral antidiabetic; quaternary prevention

Introduction:

Diabetes mellitus (DM) is a prevalent chronic disease worldwide. Metformin is a drug widely used in the treatment of this disease due to its efficacy, low cost and potential to reduce the risk of cardiovascular events. It inhibits gluconeogenesis, gastrointestinal absorption of glucose and improves insulin sensitivity. Despite being well tolerated and safe, it has the potential to cause various adverse effects, with gastrointestinal ones being the most common and lactic acidosis the rarest.

Case:

A 70-year-old woman with a personal history of asthma, obstructive sleep apnea syndrome, type 2 DM, hypertension and breast carcinoma, medicated for her pathologies, including a daily dose of 2 grams of metformin, went to the emergency department due to dyspnea associated with upper quadrant abdominal pain, after having undergone upper and lower digestive endoscopies 3 days earlier. On admission, she was agitated, hypotensive, tachycardic and tachypneic, with dehydrated mucous membranes. Analytically there was acute kidney injury (creatinine 8.57 mg/dL and urea 177 mg/dL) and severe metabolic acidosis (pH 6.734, HCO3- 2.5 mEq/L and lactates 19.2 mmol/L). She was then diagnosed with metformin-associated lactic acidosis, requiring hospitalization for 7 days. She was discharged hemodynamically stable, asymptomatic and medicated with empagliflozin 10mg and linagliptin 5mg, after suspension of the oral antidiabetic previously instituted.

Discussion:

Dehydration, in this case associated with intestinal preparation for digestive endoscopies, is a predisposing factor for renal failure which reduces the elimination of metformin through kidneys, increasing its plasma levels, especially if metformin administration is continued. The management of severe metabolic acidosis associated with metformin requires aggressive treatment to correct the metabolic disorder. The family doctor has a key role in managing therapy and counseling diabetic patients before diagnostic procedures or in the event of acute illnesses. It is essential to make patients and medical staff aware of this scenario.

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