Are fluoroquinolones (FQs) safe to use in patients with myasthenia gravis (MG)?

Fluoroquinolones Should Be Avoided in Patients with Myasthenia Gravis

Fluoroquinolones should be strictly avoided in patients with myasthenia gravis due to their potential to cause life-threatening exacerbations of the disease. 1, 2

Mechanism and Evidence

Fluoroquinolones can trigger myasthenia gravis exacerbations through neuromuscular blockade:

• Studies demonstrate that fluoroquinolones progressively decrease the amplitude of miniature endplate potentials and currents at the neuromuscular junction 3
• Exacerbations typically develop rapidly, with a median onset of just 1 day following fluoroquinolone exposure 2
• Clinical manifestations include:
  • Generalized muscle weakness (54% of cases)
  • Dyspnea (51% of cases)
  • Myasthenic crisis requiring ventilatory support (30% of cases)
  • Dysphagia (24% of cases)
  • Diplopia and ptosis (16% of cases each)
  • Death (5% of cases) 2

Clinical Impact and Risk Assessment

The risk is substantial and well-documented:

• A review of FDA Adverse Event Reporting System identified 37 cases of myasthenia gravis exacerbation following fluoroquinolone exposure 2
• Multiple fluoroquinolones have been implicated, including levofloxacin, moxifloxacin, ciprofloxacin, ofloxacin, gatifloxacin, norfloxacin, and trovafloxacin 2
• Positive rechallenge (recurrent exacerbation upon reintroduction) was documented in 16% of cases, confirming causality 2
• Exacerbations can occur with a single dose, as demonstrated in a case where symptoms developed within one hour of administration 4

Management Recommendations

When treating infections in patients with myasthenia gravis:

1. Avoid all fluoroquinolones in patients with myasthenia gravis 1
2. Use safer antibiotic alternatives including:
   • Penicillins
   • Cephalosporins
   • Tetracyclines (including tigecycline) 1
3. Also avoid other neuromuscular blocking antibiotics such as:
   • Aminoglycosides
   • Macrolide antibiotics 1

Special Considerations

• Patients with generalized myasthenia gravis appear to be more vulnerable to drug-induced exacerbations than those with stable, localized disease 5
• If a patient with myasthenia gravis develops worsening symptoms after starting any new medication, the drug should be immediately withdrawn 5
• Symptom severity can range from mild weakness to life-threatening respiratory compromise requiring ventilatory support 2, 6

Monitoring and Response

If a patient with myasthenia gravis has been exposed to fluoroquinolones:

• Monitor closely for signs of exacerbation, particularly respiratory function
• Be prepared for rapid intervention, as symptoms can progress quickly
• Discontinue the fluoroquinolone immediately if symptoms worsen
• Implement appropriate myasthenia gravis crisis management if needed

The evidence clearly demonstrates that the risk of using fluoroquinolones in patients with myasthenia gravis far outweighs any potential benefits, especially given the availability of safer antibiotic alternatives.