What antibiotics are compatible with Myasthenia Gravis (MG)?

Antibiotics Compatible with Myasthenia Gravis

Patients with myasthenia gravis should avoid fluoroquinolones, aminoglycosides, and macrolide antibiotics as these medications can worsen myasthenic symptoms and potentially precipitate a myasthenic crisis. 1

High-Risk Antibiotics to Avoid in MG

• Aminoglycosides (e.g., gentamicin, tobramycin, amikacin) can block neuromuscular transmission and precipitate weakness, even when used topically as eye drops 1, 2
• Fluoroquinolones (e.g., levofloxacin, ciprofloxacin, moxifloxacin) have neuromuscular blocking activity and can exacerbate muscle weakness in persons with myasthenia gravis 1, 3, 4
• Macrolide antibiotics (e.g., azithromycin, erythromycin) should be avoided as they can worsen myasthenic symptoms 1, 5

Safer Antibiotic Options for MG Patients

• Penicillins are generally considered safer options, though rare cases of exacerbation have been reported with amoxicillin 6, 7
• Tetracyclines may be used with caution in MG patients, with tigecycline specifically reported as successful in treating community-acquired pneumonia in a MG patient 8
• Bacitracin (topical) appears to be safe for use in MG patients based on ophthalmic guidelines 9

Risk Assessment and Monitoring

• The risk of antibiotic-associated MG exacerbation appears to be relatively low (less than 2.5% for fluoroquinolones and macrolides) but can be severe when it occurs 7
• Risk factors for antibiotic-associated MG exacerbation include:
  • Recent MG-related hospitalization or ED visit in the preceding 6 months 7
  • Female sex 7
  • Diabetes 7
  • Underlying infection itself may contribute to exacerbation 7

Management Recommendations

• For patients requiring antibiotics, consult with neurology for antibiotic selection when treatment is necessary 1
• If a patient with MG develops worsening symptoms after antibiotic administration, the antibiotic should be discontinued immediately 1, 6
• Monitor patients closely for signs of respiratory compromise, as antibiotic-induced exacerbations can progress to myasthenic crisis requiring ventilatory support 5, 1
• For severe infections requiring antibiotics with known risk in MG, consider:
  • More frequent monitoring of respiratory function 10
  • Having rescue therapies available (e.g., IVIG, plasma exchange) 10
  • ICU-level monitoring if high-risk antibiotics must be used 5

Special Considerations

• When treating blepharitis in MG patients, topical bacitracin or erythromycin ointment may be used, but erythromycin should be used with caution due to its macrolide classification 9
• For patients with renal impairment, dose adjustments may be required for certain antibiotics, with macrolides requiring a 50% dose reduction when GFR < 30 ml/min/1.73 m² 9
• Tetracyclines should be reduced in dose when GFR < 45 ml/min/1.73 m² as they can exacerbate uremia 9

By carefully selecting antibiotics and monitoring patients closely, infections can be effectively treated while minimizing the risk of myasthenic exacerbation in patients with MG.