What is the recommended IVIG (Intravenous Immunoglobulin) dose for treating myasthenia gravis?

IVIG Dosing in Myasthenia Gravis

The recommended IVIG dose for treating myasthenia gravis is 2 g/kg total dose, typically administered as 0.4 g/kg/day over 5 consecutive days. 1

Dosing Protocol

• Initial dosing: 0.4 g/kg/day for 5 consecutive days (total dose 2 g/kg)
• Maximum daily dose: 80 g/day
• Administration: Divided over 2-5 days depending on patient tolerance and clinical setting

Clinical Indications for IVIG in Myasthenia Gravis

IVIG is primarily indicated for:

• Severe exacerbations (Grade 3-4) requiring hospitalization
• Myasthenic crisis with respiratory compromise
• Pre-thymectomy stabilization
• Inadequate response to first-line treatments

Treatment Algorithm

1. For myasthenic crisis or severe exacerbation (Grade 3-4):

   • Admit patient, consider ICU monitoring
   • Consult neurology
   • Initiate IVIG at 0.4 g/kg/day for 5 days (total 2 g/kg) 1
   • Consider concurrent corticosteroids (prednisone 1-1.5 mg/kg PO daily)
   • Monitor pulmonary function and neurologic status daily

2. For moderate exacerbations (Grade 2):

   • Consider pyridostigmine (starting at 30 mg PO TID, maximum 120 mg QID)
   • If inadequate response, add corticosteroids
   • If still inadequate, consider IVIG at standard dosing

Monitoring During IVIG Administration

• Vital signs and respiratory parameters
• Negative Inspiratory Force (NIF) measurements
  • NIF > -60 cm H₂O: Continue routine monitoring
  • NIF -20 to -60 cm H₂O: Close monitoring and potential intervention 2
• Watch for infusion-related reactions
• Monitor for fluid overload in patients with cardiac or renal compromise

Maintenance Therapy Considerations

While the American Society of Clinical Oncology guidelines focus on acute management, some patients may require maintenance therapy:

• Maintenance dosing typically ranges from 0.4-1 g/kg every 3-4 weeks 3
• Consider maintenance therapy when:
  • Patients fail to respond adequately to conventional immunosuppressive therapy
  • Patients cannot tolerate standard immunosuppressive medications
  • Rapid tapering of corticosteroids is needed

Important Caveats and Pitfalls

• Recent evidence caution: A 2023 randomized controlled trial found that IVIG was not more effective than placebo in reducing corticosteroid dose in MG patients 4, suggesting its effects may not be synergistic with corticosteroids.
• Alternative therapy: Consider plasmapheresis as an alternative to IVIG in patients who don't respond or have contraindications to IVIG 1.
• Medication avoidance: During IVIG treatment, avoid medications that can worsen myasthenia, including β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides 1.
• Cost considerations: IVIG is expensive and may require insurance authorization; plan accordingly to avoid treatment delays.
• Adverse effects: Monitor for headache, aseptic meningitis, thrombotic events, and renal dysfunction.

Special Populations

• Elderly patients: May require slower infusion rates and vigilant monitoring for volume overload
• Renal impairment: Consider dose reduction and slower infusion rates
• IgA deficiency: Screen for IgA deficiency before first dose due to risk of anaphylaxis

By following this evidence-based dosing protocol and monitoring plan, IVIG can be effectively and safely administered to patients with myasthenia gravis requiring immunomodulatory therapy.