MKSAP Quiz: Elderly patient with episodes of confusion
This month's quiz asks readers to evaluate an 82-year-old with a 6-year history of type 2 diabetes mellitus and a 5-year history of heart failure.
An 82-year-old woman is evaluated for the recent development of frequent episodes of confusion and forgetfulness. She has a 6-year history of type 2 diabetes mellitus and a 5-year history of heart failure. Medications are glyburide, furosemide, lisinopril, and potassium supplements.
On physical examination, temperature is normal, blood pressure is 142/77 mm Hg, pulse rate is 87/min, and respiration rate is 16/min; BMI is 20. All other physical examination findings are unremarkable, including those from a mental status examination.
Laboratory studies show a serum creatinine level of 1.3 mg/dL (115 µmol/L) and a hemoglobin A1c value of 6.2%.
Which of the following is the most appropriate immediate next step in management?
A. Discontinue glyburide
B. Start glipizide
C. Start metformin
D. Start premixed 70/30 insulin (neutral protamine Hagedorn [NPH] insulin/regular
insulin)
MKSAP Answer and Critique
The correct answer is A. Discontinue glyburide. This item is available to MKSAP 16 subscribers as item 53 in the Endocrinology section. Information about MKSAP 16 is available online.
This patient should stop taking glyburide immediately. She has impaired kidney function and heart failure, both of which significantly impair her ability to clear glyburide and glyburide metabolites from her body. The biologic half-life of glyburide is thus prolonged. Because of this long half-life and the degree of this patient's kidney impairment (estimated glomerular filtration rate <50 mL/min/1.73 m2), merely decreasing her glyburide dosage is insufficient to reliably decrease blood drug levels and prevent the return of hypoglycemia. A hemoglobin A1c value of 6.2% is dangerously low in an older patient with diabetes mellitus and has most likely resulted in frequent episodes of hypoglycemia. These episodes, in turn, have caused her recent episodes of confusion and forgetfulness. Because it may take several days after discontinuation for the glyburide to decrease to undetectable levels, evaluating her plasma glucose level in 2 weeks would be appropriate as a next step in management.
Although glipizide is safer and has a shorter half-life than glyburide, it also accumulates in patients with chronic kidney disease. More importantly, no hypoglycemic agent (glipizide, metformin, or insulin) should be given to this patient until glyburide is completely cleared from her body, which would completely end the cycle of recurrent hypoglycemic episodes.
Key Point
- Sulfonylureas with long half-lives, such as glyburide, should not be used in older patients with type 2 diabetes mellitus and impaired kidney function or heart failure.