Severe hypoglycemia in an elderly patient treated with metformin

The following case of severe hypoglycemia was reported during a systematic evaluation of hospital admissions caused by adverse drug reactions (supported by BfArM).

A 79-year-old diabetic woman was admitted to hospital in a stuporous and unresponsive state. The initial physical examination revealed no other abnormal findings. Serum blood glucose was found to be 2.0 mmol/l and HbA1c was 4.6%. The patient had been started on antidiabetic therapy with metformin 2 months earlier. Treatment with other drugs being taken at that time, an ACE inhibitor, an NSAID and nitrofurantoin, remained unchanged. DIAGNOSIS, TREATMENT AND FOLLOW-UP: Laboratory tests excluded lactic acidosis and renal insufficiency. Cerebral computed tomography findings were normal. The patient improved dramatically following administration of glucose. Other laboratory findings confirmed the diagnosis of hypoglycemia. Blood glucose concentrations ranged between 4.0 and 10.0 mmol/l in the subsequent days and the patient could be discharged in full health.

Drug-induced hypoglycemia is possible even in diabetics not receiving insulin or oral antidiabetic agents increasing insulin secretion. The risk of drug-induced hypoglycemia should be particularly considered when drugs containing blood glucose-lowering components are combined. Metformin does not usually cause hypoglycemia when administered as monotherapy. We suspected that hypoglycemia in this patient was caused by additional blood glucose-lowering effects of the ACE inhibitor and the NSAID possibly combined with a suboptimal nutrition. The indications for metformin administration undergo critical scrutiny.