Sulfonylurea Selection and Prescription for Type 2 Diabetes
For this patient on maximal metformin with normal renal function, prescribe glipizide 5 mg once daily, taken 30 minutes before breakfast, with a 30-day supply (#30 tablets). 1
Rationale for Glipizide Selection
Glipizide is the preferred sulfonylurea in this clinical scenario because it has inactive metabolites and does not accumulate in renal insufficiency, minimizing hypoglycemia risk even though this patient currently has normal renal function. 2
Key advantages of glipizide over other sulfonylureas:
Glipizide produces inactive metabolites with minimal hypoglycemic potency, unlike glyburide (glibenclamide) which accumulates active compounds that significantly increase hypoglycemia risk. 2
Long-acting sulfonylureas like glyburide should not be used at any eGFR level, while short-acting agents like glipizide can be used cautiously even at eGFR <30 mL/min/1.73 m² with dose reduction. 3
Glipizide has comparable or superior efficacy to other sulfonylureas in controlling fasting blood glucose in Type 2 diabetes. 4
Prescription Details
Starting dose and administration:
The FDA-approved starting dose is 5 mg given approximately 30 minutes before breakfast to achieve the greatest reduction in postprandial hyperglycemia. 1
Geriatric patients or those with liver disease should start at 2.5 mg, but this patient does not meet these criteria. 1
Titration plan:
Dosage adjustments should be in increments of 2.5–5 mg based on blood glucose response, with at least several days between titration steps. 1
The maximum recommended once-daily dose is 15 mg; doses above 15 mg should be divided and given before meals. 1
The maximum total daily dose is 40 mg, though doses above 30 mg should be given twice daily. 1
Critical Safety Considerations
Hypoglycemia prevention:
Instruct the patient to take glipizide with adequate caloric content and monitor for hypoglycemia symptoms, particularly during the first few weeks of therapy. 1
Glipizide generally carries lower hypoglycemia risk compared to other sulfonylureas like glyburide, but vigilance remains essential. 5, 2
Monitoring requirements:
Monitor blood glucose periodically to detect primary failure (inadequate glucose lowering at maximum dose) or secondary failure (loss of effectiveness after initial response). 1
Check HbA1c levels to monitor long-term glycemic control and treatment response. 1
Important Clinical Pitfall
While sulfonylureas remain a traditional second-line option after metformin failure, current guidelines increasingly favor SGLT2 inhibitors or GLP-1 receptor agonists as second-line agents due to cardiovascular and renal benefits. 6 However, since the question specifically requests a sulfonylurea prescription, glipizide represents the safest choice within this drug class for a patient with normal renal function who may develop CKD over time given the natural history of diabetes.
Sample Prescription
Glipizide 5 mg tablets
Take 1 tablet by mouth once daily, 30 minutes before breakfast
Dispense: 30 tablets
Refills: As appropriate for ongoing care