Review Question - QID 216610

A 44-year-old nurse presents to the emergency department with confusion. This has happened several times this past month with increasing frequency. Each time her symptoms improved with eating. She is otherwise healthy. She lives with her mother who has diabetes whose medications include metformin, insulin, lisinopril, amlodipine, and glyburide. Her temperature is 98.0°F (36.7°C), blood pressure is 132/81 mmHg, pulse is 85/min, respirations are 16/min, and oxygen saturation is 98% on room air. Physical exam reveals a confused woman. She is moving all her extremities but follows commands poorly. Laboratory studies are ordered as seen below.

Hemoglobin: 14 g/dL
Hematocrit: 41%
Leukocyte count: 7,500/mm^3 with normal differential
Platelet count: 199,000/mm^3

Serum:
Na+: 140 mEq/L
Cl-: 102 mEq/L
K+: 4.0 mEq/L
HCO3-: 23 mEq/L
BUN: 30 mg/dL
Glucose: 29 mg/dL
Creatinine: 1.4 mg/dL
Ca2+: 10.2 mg/dL
Sulfonylurea level: undetectable
C-peptide level: 55 ng/mL (normal < 5 ng/mL)

Which of the following is the most likely etiology of this patient’s symptoms?