What is the initial treatment for autoimmune myasthenia gravis?

Initial Treatment for Autoimmune Myasthenia Gravis

Start pyridostigmine at 30 mg orally three times daily as the first-line treatment for autoimmune myasthenia gravis, titrating upward based on symptom response to a maximum of 120 mg four times daily. 1, 2, 3

First-Line Symptomatic Treatment

• Pyridostigmine (Mestinon) is the cornerstone of initial therapy, functioning as an acetylcholinesterase inhibitor that increases acetylcholine availability at the neuromuscular junction. 1, 2, 3
• Begin with 30 mg orally three times daily and gradually increase based on clinical response and tolerability. 1, 2
• The maximum dose is 120 mg orally four times daily. 1, 2
• This medication is FDA-approved specifically for myasthenia gravis treatment. 3

When to Escalate Beyond Pyridostigmine

For patients with Grade 2 or higher symptoms who have insufficient control with pyridostigmine alone, add corticosteroids directly. 1

• Initiate prednisone at 1-1.5 mg/kg orally daily for moderate to severe disease (MGFA Class III-V). 1, 2
• For mild disease (MGFA Class I-II), consider starting with 0.5-1 mg/kg orally daily if pyridostigmine is inadequate. 2
• Taper corticosteroids gradually based on symptom improvement. 1

Management of Severe Exacerbations (Grade 3-4)

For myasthenic crisis with respiratory compromise or severe generalized weakness, immediately hospitalize with ICU-level monitoring and initiate IVIG or plasmapheresis. 1, 2

• Administer IVIG at 2 g/kg total dose over 5 days (0.4 g/kg/day for 5 consecutive days). 1, 2
• Plasmapheresis is an alternative when IVIG is contraindicated or not feasible. 1
• Continue corticosteroids concurrently during acute treatment. 1
• Perform frequent pulmonary function assessments with negative inspiratory force and vital capacity monitoring. 1, 2

Critical Medications to Avoid

Educate patients to strictly avoid medications that worsen myasthenic symptoms: 1, 4, 2

• β-blockers 1, 4, 2
• Intravenous magnesium 1, 4, 2
• Fluoroquinolone antibiotics 1, 4, 2
• Aminoglycoside antibiotics 1, 4, 2
• Macrolide antibiotics 1, 4, 2

Essential Diagnostic Workup Before Treatment

• Test for acetylcholine receptor (AChR) antibodies; if negative, test for muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4) antibodies. 1, 2
• Perform pulmonary function testing with negative inspiratory force and vital capacity. 1, 2
• Electrodiagnostic studies with repetitive stimulation and/or jitter studies confirm the diagnosis. 4, 2

Common Pitfalls to Avoid

• Do not use IVIG for chronic maintenance therapy—it is reserved only for acute exacerbations or crisis situations. 1
• Approximately 50% of patients with ocular myasthenia may show minimal response to pyridostigmine alone and will require escalation to corticosteroids. 4
• Be aware that pyridostigmine can cause bradycardia and AV block due to its cholinergic effects; monitor cardiac function, especially in older patients. 5
• Recognize that 50-80% of patients presenting with isolated ocular symptoms will develop generalized myasthenia within a few years, making early diagnosis and treatment essential. 4

Monitoring and Follow-Up

• Plan regular neurology consultation to adjust treatment as the disease evolves. 1
• Instruct patients to take pyridostigmine exactly as prescribed and to time activities around medication dosing for optimal strength. 1
• Teach patients to monitor for and immediately report worsening symptoms such as changes in speech, swallowing difficulties, respiratory problems, or double vision. 1