What is the treatment for myasthenia gravis?

Treatment of Myasthenia Gravis

The treatment of myasthenia gravis should follow a stepwise approach, starting with pyridostigmine as first-line therapy, adding corticosteroids for more than mild disease, and incorporating steroid-sparing agents, with consideration for thymectomy in appropriate patients. 1, 2

Diagnostic Confirmation

Before initiating treatment, confirm diagnosis with:

• Electrodiagnostic studies (repetitive nerve stimulation and single-fiber EMG)
• Antibody testing (AChR, MuSK, Lrp4)
• Chest imaging to evaluate for thymoma
• Clinical tests such as ice pack test or edrophonium (Tensilon) test

Treatment Algorithm

First-Line Treatment

• Pyridostigmine (Acetylcholinesterase Inhibitor)
  • Starting dose: 30 mg orally three times daily
  • Titrate up as needed based on symptoms
  • Maximum dose: 120 mg four times daily (up to 600 mg daily) 1
  • FDA-approved for treatment of myasthenia gravis 2
  • Suitable for long-term treatment in milder disease 3

Second-Line Treatment (For More Than Mild Disease)

• Corticosteroids
  • Prednisone 0.5-1.5 mg/kg orally daily
  • Positive response rate: 66-85% 1
  • Important: Start steroid-sparing agents concurrently to minimize steroid exposure

Steroid-Sparing Agents

• Azathioprine: 2 mg/kg of ideal body weight in divided doses
• Methotrexate: 15 mg weekly
• Mycophenolate mofetil: Start at 500 mg twice daily, increase to 1000 mg twice daily 1

Thymectomy

• Indicated for all patients with thymoma
• Beneficial in AChR antibody-positive generalized MG up to age 65
• Can lead to remission rates of approximately 11.6% 1, 4

Crisis Management

• Hospital admission and ICU monitoring
• Treatment options:
  • IVIG: 2 g/kg over 5 days
  • Plasmapheresis: for 5 days 1
• Close monitoring of respiratory function with Negative Inspiratory Force (NIF) measurements

Special Considerations

Respiratory Monitoring

• Regular pulmonary function tests
• NIF and vital capacity measurements
• Intervention needed for NIF -20 to -60 cm H₂O 1

Medications to Avoid

• β-blockers
• IV magnesium
• Fluoroquinolones
• Aminoglycosides
• Macrolides 1

Anesthesia Considerations

• Safe anesthetic agents: Propofol, Sevoflurane, isoflurane, Fentanyl, remifentanil, Lidocaine, bupivacaine
• Avoid: Atracurium, mivacurium, succinylcholine
• Preferred neuromuscular blocker: Rocuronium (can be antagonized with sugammadex) 1

Treatment for Refractory Cases

For patients who fail to respond to conventional therapy:

• Rituximab 5, 6
• Cyclophosphamide 6
• Tacrolimus 6
• Repeated courses of IVIG or plasmapheresis 5

Monitoring and Follow-up

• Regular neurological assessments
• Pulmonary function tests
• Medication adjustments based on clinical response
• Follow-up with neuromuscular specialist 1

Common Pitfalls to Avoid

1. Delayed immunosuppression: Don't rely solely on pyridostigmine for moderate to severe disease
2. Inadequate steroid-sparing strategy: Start steroid-sparing agents concurrently with corticosteroids
3. Missing thymoma: Always perform chest imaging at diagnosis
4. Overlooking respiratory compromise: Monitor NIF and vital capacity regularly
5. Medication interactions: Be vigilant about medications that can worsen myasthenia gravis

The treatment approach should be ambitious, aiming for clinical remission or minimal manifestations with near-normal function and quality of life 7. Early intervention with appropriate therapy can significantly improve outcomes and reduce disability.