How to initiate metformin in a patient with HbA1c 7.4% on Lantus (insulin glargine) 25 units bid and Jardiance (empagliflozin) 25mg?

Initiating Metformin in a Patient with HbA1c 7.4% on Lantus and Jardiance

For a patient with HbA1c 7.4% on Lantus 25 units BID and Jardiance 25mg, metformin should be started at 500mg once daily with a meal, then gradually titrated to 1000mg twice daily over 2-4 weeks to minimize gastrointestinal side effects while optimizing glycemic control. 1

Rationale for Adding Metformin

• Metformin is the first-line pharmacological treatment for patients with elevated insulin resistance values, particularly in overweight patients 1
• Adding metformin to the current regimen is appropriate as:
  • The patient's HbA1c of 7.4% indicates suboptimal glycemic control
  • Metformin works synergistically with SGLT2 inhibitors like Jardiance (empagliflozin) 2
  • The combination of empagliflozin and metformin has shown superior HbA1c reduction compared to either agent alone 3

Specific Dosing and Titration Schedule

1. Initial dose: Start with 500mg once daily with the largest meal
2. Week 1: 500mg once daily with dinner
3. Week 2: Increase to 500mg twice daily (morning and evening with meals)
4. Week 3-4: Increase to 1000mg in morning and 500mg in evening
5. Week 4-5: Target dose of 1000mg twice daily (if tolerated)

Monitoring and Follow-up

• Schedule follow-up within 2 weeks for initial medication adjustment
• Monitor for gastrointestinal side effects (nausea, diarrhea, abdominal discomfort)
• Assess adequacy of therapy after 3 months; if target not achieved, consider further adjustments 1
• Monitor for vitamin B12 deficiency in patients on long-term metformin 1

Insulin Adjustment Considerations

• As metformin takes effect, insulin requirements may decrease
• Consider reducing Lantus by 10-20% (approximately 2-5 units per dose) if:
  • Fasting blood glucose consistently <100 mg/dL
  • Any episodes of hypoglycemia occur
• Monitor blood glucose more frequently during the first 2 weeks of metformin initiation

Potential Benefits of This Approach

• The combination of empagliflozin and metformin has shown HbA1c reductions of 1.9-2.1% in clinical trials 3
• Weight reduction benefits: metformin is weight neutral to slightly weight reducing, complementing the weight loss effects of empagliflozin 4
• Reduced insulin requirements, potentially decreasing hypoglycemia risk 5

Common Pitfalls to Avoid

• Starting with too high a dose: This increases GI side effects and may lead to poor adherence
• Not titrating to effective dose: Metformin's full benefits are typically seen at 1500-2000mg daily
• Ignoring renal function: Ensure eGFR is >30 mL/min before starting metformin
• Failing to adjust insulin: As glucose control improves with metformin, insulin needs may decrease, requiring proactive dose adjustment to prevent hypoglycemia

By following this structured approach to initiating metformin, you can optimize glycemic control while minimizing side effects in this patient already on Lantus and Jardiance.