Infusion Therapy for Myasthenia Gravis
For adults with myasthenia gravis requiring rapid immunomodulation during acute exacerbation or pre-operative preparation, administer intravenous immunoglobulin (IVIG) at 2 g/kg divided over 5 days (0.4 g/kg/day) or plasmapheresis for 5 days, combined with corticosteroids. 1
Severity-Based Treatment Algorithm
Grade 2 (Moderate Symptoms)
For patients with mild generalized weakness interfering with activities of daily living but without respiratory compromise:
- Hold immunotherapy if applicable
- Start pyridostigmine 30 mg PO three times daily, titrating up to maximum 120 mg four times daily
- Initiate corticosteroids: prednisone 0.5-1.5 mg/kg PO daily
- Strongly consider inpatient admission as deterioration can occur rapidly 2
Grade 3-4 (Severe/Life-Threatening)
For patients with self-care limitations, dysphagia, facial weakness, respiratory muscle weakness, or rapidly progressive symptoms:
- Admit to hospital with ICU-level monitoring capability
- IVIG: 2 g/kg IV over 5 days (0.4 g/kg/day) 1, 2
- Alternative: Plasmapheresis for 5 days (3-5 sessions at 200-250 ml/kg) 1
- Continue corticosteroids (methylprednisolone 2-4 mg/kg/day IV or prednisone 1-1.5 mg/kg PO)
- Begin steroid taper 3-4 weeks after initiation based on symptom improvement 2
- Frequent pulmonary function monitoring (negative inspiratory force and vital capacity)
- Daily neurologic evaluation
- Mandatory neurology consultation 1
Evidence Quality and Nuances
The ASCO guidelines 1, 2 provide the most comprehensive framework, though they focus on immune checkpoint inhibitor-related myasthenia gravis. The principles apply broadly to all myasthenia gravis exacerbations. A 2008 randomized controlled trial 3 definitively demonstrated IVIG efficacy at 2 g/kg over 2 days, with significant improvement in Quantitative MG Score at day 14 persisting through day 28. The largest clinical benefit occurred in patients with more severe disease.
Regarding dosing, a 2005 multicenter RCT 4 found no significant superiority of 2 g/kg over 1 g/kg IVIG (effect size 3.84,95% CI -1.03 to 8.71, P=0.12), though the 2 g/kg dose remains standard based on the positive 2008 trial and guideline recommendations.
Pre-operative Preparation
For thymectomy or other surgical procedures, the evidence is mixed. A 2026 systematic review 5 found that postoperative myasthenic crisis incidence has declined below 10% with modern surgical techniques. Routine preoperative IVIG or plasmapheresis is not recommended for all patients. Instead, use risk stratification:
High-risk features warranting preoperative immunomodulation:
- Bulbar involvement
- Reduced pulmonary function (vital capacity <2L or negative inspiratory force <-30 cmH2O)
- Prior myasthenic crisis
- Elevated risk scores (Leuzzi or Kanai models) 5
For high-risk patients, administer IVIG 2 g/kg over 5 days or plasmapheresis 1-2 weeks before surgery.
Critical Safety Considerations
Medications to avoid (can worsen myasthenia): 1, 2
- β-blockers
- IV magnesium
- Fluoroquinolones
- Aminoglycosides
- Macrolide antibiotics
Monitor for concurrent conditions:
- Myocarditis (check troponin, ECG, echocardiogram if respiratory insufficiency or elevated CPK) 1
- Myositis (CPK, aldolase, ESR, CRP) 1
Timing Considerations
Plasmapheresis immediately after IVIG will remove the immunoglobulin 2—do not administer sequentially. Choose one modality or allow adequate washout period (typically 2-4 weeks) between treatments.
IVIG demonstrates rapid onset of effect, typically within 2 weeks, making it ideal for acute exacerbations 3. The response persists for approximately 4-8 weeks, after which maintenance immunosuppression should be optimized.
Refractory Cases
If no response to initial IVIG or plasmapheresis:
- Consider rituximab for refractory disease 2
- Emerging data supports efgartigimod (FcRn antagonist) for rapid IgG reduction, particularly in anti-MuSK antibody-positive patients 6
- Eculizumab (complement inhibitor) shows promise in perioperative settings 7
The key principle is early aggressive treatment prevents respiratory failure and reduces mortality—do not delay immunomodulation in moderate-to-severe cases while awaiting antibody results or specialist consultation.