Should metformin be stopped in patients with Urinary Tract Infections (UTIs)?

Management of Metformin in Patients with Urinary Tract Infections

Metformin should be temporarily discontinued in patients with urinary tract infections (UTIs) who have signs of sepsis, hemodynamic instability, or impaired renal function, but can be continued in patients with uncomplicated UTIs who remain stable and have adequate renal function. 1

Risk Assessment for Metformin Continuation in UTI

When to Stop Metformin

• Severe/Complicated UTI with:
  • Signs of sepsis or hemodynamic instability
  • Acute kidney injury (AKI) or deteriorating renal function
  • eGFR < 30 mL/min/1.73m² (absolute contraindication) 1
  • Hypoxemia or impaired tissue perfusion
  • Concurrent use of certain antimicrobials (especially fluoroquinolones and sulfamethoxazole-trimethoprim) that interact with sulfonylureas 1

When Metformin Can Be Continued

• Uncomplicated UTI with:
  • Stable vital signs
  • No signs of sepsis
  • Preserved renal function (eGFR ≥ 45 mL/min/1.73m²) 1
  • Absence of hypoxemia or impaired tissue perfusion

Rationale for Temporary Discontinuation

The primary concern with metformin during acute infections is the risk of lactic acidosis, which although rare, can be life-threatening. This risk increases in conditions that may cause:

1. Impaired metformin clearance: Acute kidney injury can occur during severe infections 1
2. Increased anaerobic metabolism: Sepsis and hypoxemia promote lactate production 1
3. Impaired lactate clearance: Liver dysfunction during severe illness 1

Monitoring and Management Approach

For Patients with Uncomplicated UTI

• Continue metformin if eGFR ≥ 45 mL/min/1.73m²
• Monitor renal function closely
• Ensure adequate hydration
• Watch for signs of clinical deterioration

For Patients with Complicated UTI or Sepsis

1. Temporarily discontinue metformin
2. Switch to insulin therapy for glycemic control during acute illness 1
3. Monitor for:
   • Signs of lactic acidosis (nausea, vomiting, abdominal pain, hyperventilation)
   • Changes in renal function
   • Resolution of infection

When to Restart Metformin

Metformin can be restarted when:

• Infection is controlled
• Patient is hemodynamically stable
• Renal function has returned to baseline
• No evidence of tissue hypoxia or shock 2

Special Considerations

• Recent research suggests that metformin use is associated with lower mortality due to UTI or sepsis in patients with type 2 diabetes 3, but this does not override the need to temporarily discontinue in acute severe illness
• Patients on concurrent sulfonylureas and antimicrobials (especially fluoroquinolones and sulfamethoxazole-trimethoprim) require close monitoring for hypoglycemia 1
• For patients with eGFR 30-45 mL/min/1.73m², consider dose reduction and more frequent monitoring 1

Key Pitfalls to Avoid

1. Failing to assess renal function before and during UTI treatment
2. Not recognizing early signs of sepsis that would warrant metformin discontinuation
3. Overlooking drug interactions between antimicrobials and diabetes medications
4. Automatic discontinuation of metformin in all UTIs regardless of severity (unnecessary in uncomplicated cases)
5. Not having an alternative glycemic control plan when metformin is discontinued

By following these guidelines, clinicians can appropriately manage metformin therapy in patients with UTIs, balancing the benefits of continued diabetes control against the risks of rare but serious complications like lactic acidosis.