There is No Direct Dose Equivalent Between Farxiga and Glipizide
These medications work through completely different mechanisms and cannot be converted on a milligram-to-milligram basis. Glipizide is a sulfonylurea that stimulates pancreatic insulin secretion, while Farxiga (dapagliflozin) is an SGLT2 inhibitor that increases urinary glucose excretion independent of insulin 1, 2.
Standard Dosing When Switching
If transitioning from glipizide 20 mg daily to dapagliflozin, the standard dose is 10 mg once daily, regardless of the previous glipizide dose 1. This is not an "equivalent" but rather the fixed therapeutic dose of dapagliflozin for glycemic control 1.
Key Dosing Considerations:
For glycemic control: Start dapagliflozin at 5 mg once daily if eGFR ≥45 mL/min/1.73 m², with possible increase to 10 mg once daily if additional glycemic control is needed 1
For cardiovascular/renal protection: Use dapagliflozin 10 mg once daily as a fixed dose if eGFR ≥25 mL/min/1.73 m², regardless of diabetes status 1
Do not initiate dapagliflozin for glycemic control if eGFR <45 mL/min/1.73 m², as glucose-lowering efficacy is significantly reduced at lower eGFR levels 1
Critical Safety Considerations When Switching
Reduce or discontinue glipizide when starting dapagliflozin to prevent hypoglycemia 1. The combination of these agents increases hypoglycemia risk, particularly since glipizide 20 mg is at the maximum dose for extended-release formulation 3.
Important Monitoring Points:
Check renal function before initiating dapagliflozin 1. This fundamentally determines whether dapagliflozin is appropriate for glycemic control versus cardiovascular/renal protection only
Assess volume status before starting, as dapagliflozin has diuretic effects 1. Consider reducing concurrent diuretic doses to prevent excessive volume depletion 1
Expect an initial eGFR dip of 3-5 mL/min/1.73 m² within the first 1-4 weeks, which is transient and reversible 1
Educate patients to withhold dapagliflozin during acute illness, particularly with reduced oral intake, fever, vomiting, or diarrhea 1
Why Modern Guidelines Favor This Switch
The American Heart Association indicates that glipizide is not a preferred agent in modern diabetes management, and SGLT2 inhibitors like dapagliflozin should be prioritized in patients with established cardiovascular disease, heart failure, or chronic kidney disease 4. This is because:
Dapagliflozin reduces cardiovascular death or heart failure hospitalization by 29% (HR 0.71,95% CI 0.55-0.92) 1
Dapagliflozin reduces kidney disease progression by 44% (HR 0.56,95% CI 0.45-0.68) 1
Dapagliflozin causes weight loss (mean -3.2 kg) versus weight gain with glipizide (mean +1.2 kg) 5
Dapagliflozin has significantly lower hypoglycemia risk (3.5%) compared to glipizide (40.8%) 5
Common Pitfalls to Avoid
Do not continue high-dose glipizide when starting dapagliflozin—this dramatically increases hypoglycemia risk 1, 4
Do not discontinue dapagliflozin if eGFR falls below 45 mL/min/1.73 m² during treatment, as cardiovascular and renal protective benefits persist even when glycemic efficacy is lost 1
Monitor for genital mycotic infections (approximately 6% with SGLT2 inhibitors versus 1% with placebo), which respond to standard treatment and rarely require discontinuation 1, 5
Counsel patients about euglycemic diabetic ketoacidosis, which can occur even with normal blood glucose levels, particularly during acute illness 1