What medications should be avoided in patients with myasthenia gravis (MG)?

Medications to Avoid in Myasthenia Gravis

Patients with myasthenia gravis should avoid beta-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolide antibiotics as these medications can worsen myasthenic symptoms and potentially precipitate a myasthenic crisis. 1

High-Risk Medications to Avoid

Antibiotics

• Aminoglycosides (gentamicin, tobramycin, amikacin) - can block neuromuscular transmission and precipitate weakness 1
• Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) - can worsen neuromuscular blockade 1
• Macrolides (azithromycin, erythromycin, clarithromycin) - can exacerbate symptoms and cause new onset of myasthenic syndrome 2
• Some penicillins - cases of MG exacerbations have been reported after amoxicillin or amoxicillin/clavulanate treatment 3

Cardiovascular Medications

• Beta-blockers (propranolol, metoprolol, atenolol) - can worsen neuromuscular weakness 1

Other Medications

• IV magnesium - can impair neuromuscular transmission 1
• Muscle relaxants - particularly important to avoid in surgical settings; if needed, monitoring of neuromuscular blockade is recommended 1

Anesthetic Considerations

Neuromuscular Blocking Agents

• Depolarizing agents (suxamethonium) - contraindicated in myasthenia gravis due to risk of prolonged effect 1
• Non-depolarizing agents - patients with MG show increased sensitivity requiring 50-75% reduction in dosing 1

Reversal Agents

• Sugammadex is recommended for reversal of steroidal muscle relaxants in MG patients when necessary 1
• Neostigmine may interfere with long-term MG treatment and should be used with caution 1

Special Considerations

Immune Checkpoint Inhibitor Therapy

• If patients with MG are receiving immune checkpoint inhibitor therapy for cancer treatment, special monitoring is required as these agents can exacerbate MG 1
• For grade 2 symptoms, hold immune checkpoint inhibitors 1
• For grade 3-4 symptoms, permanently discontinue immune checkpoint inhibitors 1

Pain Management

• Pain management in MG patients requires careful consideration as many analgesics can interact with MG medications 4
• Avoid medications with muscle relaxant properties when possible 4

Monitoring Recommendations

• When introducing any new medication in MG patients, closely monitor for increased muscle weakness 5
• Patients with generalized MG are especially vulnerable to drug-induced exacerbations 5
• If weakness worsens after starting a new medication, the drug should be withdrawn or the dose reduced 5

Safe Alternatives

• For immunosuppression: Prednisone, azathioprine, mycophenolate mofetil, and cyclosporine are commonly used and generally safe in MG 6
• For symptomatic treatment: Pyridostigmine (acetylcholinesterase inhibitor) remains the mainstay of symptomatic therapy 7
• For infections requiring antibiotics: Consider consultation with neurology for antibiotic selection when treatment is necessary 1

Remember that patients with well-controlled MG may tolerate some of these medications better than those with active disease, but caution is always warranted 5. The risk-benefit ratio must be carefully assessed when these medications cannot be avoided.