Does prednisone and erythromycin interact?

Prednisone and Erythromycin Drug Interaction

Yes, prednisone and erythromycin have a clinically significant interaction that can increase the risk of adverse effects from prednisone. 1

Mechanism of Interaction

Erythromycin is a potent inhibitor of the cytochrome P450 enzyme system, specifically the CYP3A4 subclass, which is responsible for the metabolism of many medications including corticosteroids like prednisone 1. This interaction can lead to:

• Decreased clearance of prednisone
• Increased serum concentrations of prednisone
• Prolonged therapeutic and adverse effects of prednisone

Clinical Implications

When erythromycin and prednisone are used concurrently, the following effects may occur:

• Increased risk of corticosteroid-related adverse effects:
  • Hyperglycemia
  • Hypertension
  • Immunosuppression
  • Mood changes
  • Fluid retention
  • Adrenal suppression
  • Increased susceptibility to infections

Management Recommendations

1. Consider alternative antibiotics when possible:

   • Azithromycin is preferred over erythromycin when a macrolide is needed in patients taking prednisone, as azithromycin metabolism is not affected by the cytochrome P450 system 1

2. If co-administration cannot be avoided:

   • Monitor for signs of increased corticosteroid effects
   • Consider reducing prednisone dosage by approximately 25-33% during erythromycin treatment 1
   • Resume normal prednisone dosing after discontinuation of erythromycin

3. Monitoring parameters:

   • Blood pressure
   • Blood glucose levels
   • Signs of infection
   • Mental status changes
   • Fluid retention

Special Considerations

• Duration of interaction: The effects of this interaction may persist for several days after discontinuation of erythromycin due to the time required for enzyme activity to return to baseline

• Patients at higher risk:

  • Elderly patients
  • Patients with diabetes
  • Patients with cardiovascular disease
  • Patients on long-term corticosteroid therapy
  • Patients with hepatic impairment

Other Important Drug Interactions with Erythromycin

Erythromycin also interacts with numerous other medications through CYP3A4 inhibition, including:

• Statins (particularly lovastatin, simvastatin) 2
• Warfarin 1
• Carbamazepine 3
• Cyclosporine 1
• Tacrolimus 1
• Triazolam and other benzodiazepines 1

This highlights the importance of reviewing the complete medication list when prescribing erythromycin to any patient.