Life-Threatening Metabolic Coma Caused by Levofloxacin

Patients with diabetes mellitus are often susceptible to hypoglycemic episodes while on therapy. Most of these are attributed to inappropriate dosing of hypoglycemic agents, dietary indiscretion, or acute illness. Medications being used concomitantly should be reviewed closely when the etiology of hypoglycemia is unclear. A fifty-six-year-old woman with a history of diabetes mellitus (on metformin monotherapy) was found unresponsive at home. Her fingerstick glucose was 15 mg/dL for which she received 50% dextrose intravenously. The patient never had any previous documented hypoglycemic episodes. She had recently been diagnosed with pneumonia and was prescribed oral levofloxacin therapy. The patient had taken 4 doses of levofloxacin before the onset of hypoglycemia. These episodes recurred over the next 2 days needing close intensive care unit monitoring, dextrose infusion, and glucagon administration. Basic blood/urine investigations, cortisol and thyroid profile were normal except for low blood glucose and renal insufficiency (serum creatinine 1.4 mg/dL and creatinine clearance 42 mL/min). HbA1c was 6.8% (4.4%-6.4%), insulin 51.3 U/mL (2.6-24.9 U/mL), IGF-1 301 ng/mL(27-223 ng/mL), and C peptide 9.3 ng/mL (0.8-3.5 ng/mL). These levels were elevated but were deemed nondiagnostic because of fluctuating glucose values after glucagon administration. A blood screen for sulfonylureas and metaglinides was negative. A seventy-two-hour fast was performed to rule out hyperinsulinemic hypoglycemic syndromes; however, blood glucose values remained consistently above 120 mg/dL during this period. Thus, after exclusion of other causes, we utilized the adverse drug reaction probability scale and concluded that hypoglycemia was probably related to recent use of levofloxacin.