Certified Diabetes Care and Education Specialist (CDCES) Practice Exam

Which class of oral medications for type 2 diabetes relies on the kidneys to excrete glucose through urine, and should not be used in patients with an eGFR less than 30?

1. Sulfonylureas (glyburide, glipizide)

2. Biguanides (metformin)

3. SGLT2 inhibitors (canagliflozin)

4. DPP4 inhibitors (sitagliptin)

The correct answer is: SGLT2 inhibitors (canagliflozin)

The correct choice relies on the mechanism of action of the SGLT2 inhibitors, which work by inhibiting the sodium-glucose cotransporter 2 (SGLT2) in the kidneys. This action leads to increased excretion of glucose in the urine, thereby lowering blood glucose levels. The effectiveness of this class of medications depends significantly on renal function. In patients with an estimated glomerular filtration rate (eGFR) of less than 30 mL/min, the use of SGLT2 inhibitors is generally contraindicated. This is because the reduced kidney function may lead to a diminished ability to excrete the glucose properly, which can increase the risk of adverse effects such as urinary tract infections and dehydration. Understanding the renal implications associated with SGLT2 inhibitors is crucial for safe prescribing practices. The other classes mentioned, such as sulfonylureas, biguanides, and DPP4 inhibitors, operate through different mechanisms and have varying renal contraindications or considerations, making them less directly associated with the eGFR threshold highlighted in this question.