Is metformin (biguanide oral hypoglycemic) contraindicated in patients with Fournier's gangrene?

Metformin is NOT Contraindicated in Fournier's Gangrene

Metformin is not specifically contraindicated in patients with Fournier's gangrene, but should be temporarily discontinued during the acute phase of illness due to the risk of lactic acidosis in critically ill patients. 1

Rationale for Recommendation

Metformin Use in Critically Ill Patients

• Metformin should be temporarily discontinued during serious intercurrent illnesses that increase the risk of acute kidney injury (AKI), including:
  • Sepsis (common in Fournier's gangrene)
  • Hypotension
  • Dehydration
  • Major surgery 1

Specific Contraindications for Metformin

Metformin has specific contraindications that should be considered when managing patients with Fournier's gangrene:

1. Renal function impairment:

   • Continue if GFR ≥45 mL/min/1.73m²
   • Review use if GFR 30-44 mL/min/1.73m²
   • Discontinue if GFR <30 mL/min/1.73m² 1

2. Acute conditions that may alter renal function:

   • Dehydration
   • Severe infection (including Fournier's gangrene)
   • Shock
   • Intravascular administration of iodinated contrast agents 2

3. Acute or chronic conditions that may cause tissue hypoxia:

   • Cardiogenic or distributive shock
   • Respiratory failure
   • Recent myocardial infarction
   • Sepsis 1, 2

Management of Metformin in Patients with Fournier's Gangrene

Acute Phase Management

1. Temporarily discontinue metformin during the acute phase of Fournier's gangrene due to:

   • Risk of AKI from sepsis and hemodynamic instability
   • Increased risk of lactic acidosis in critically ill patients 1
   • Potential for dehydration and electrolyte abnormalities

2. Monitor renal function closely:

   • Check serum creatinine and eGFR regularly
   • Assess for signs of lactic acidosis (elevated anion gap, metabolic acidosis) 2

Resumption of Metformin

Metformin can be resumed when:

• The patient is hemodynamically stable
• Acute infection is controlled
• Renal function has stabilized at baseline
• No evidence of tissue hypoxia or shock 1

Fournier's Gangrene and Diabetes Medications

It's worth noting that SGLT2 inhibitors (not metformin) have been associated with an increased risk of Fournier's gangrene:

• Multiple case reports document Fournier's gangrene in patients taking SGLT2 inhibitors 3, 4, 5, 6
• The FDA has issued warnings about this association
• Metformin has not been specifically implicated in the development of Fournier's gangrene

Key Clinical Considerations

1. Prioritize treatment of Fournier's gangrene:

   • Surgical debridement
   • Broad-spectrum antibiotics
   • Hemodynamic support 7

2. Alternative diabetes medications during acute illness:

   • Insulin is typically the preferred agent for glycemic control during acute illness
   • DPP-4 inhibitors may be considered in less severe cases with stable renal function 1, 2

3. Monitor for complications:

   • Signs of lactic acidosis (tachypnea, abdominal pain, malaise)
   • Deterioration in renal function
   • Worsening sepsis 2

In summary, while metformin is not specifically contraindicated in patients with a diagnosis of Fournier's gangrene, it should be temporarily discontinued during the acute phase of illness and can be resumed once the patient is stable, infection is controlled, and renal function has normalized.