Medication Avoidance in Myasthenia Gravis to Prevent Myasthenic Crisis

Guideline Recommendations for Contraindicated Drugs

The American Society of Clinical Oncology (ASCO) guidelines advise that β‑blockers should be avoided in patients with myasthenia gravis because they may exacerbate neuromuscular weakness. 1
The ASCO guidelines recommend avoiding intravenous magnesium in myasthenia gravis due to its potential to worsen transmission deficits. 1
According to ASCO guidance, fluoroquinolone antibiotics are contraindicated in myasthenia gravis because they can precipitate a myasthenic crisis. 2
The ASCO guidelines list aminoglycoside antibiotics as drugs to avoid in myasthenia gravis for the same reason. 1
Multiple ASCO recommendations (2018–2021) identify macrolide antibiotics as agents that should be avoided in myasthenia gravis, given their risk of triggering respiratory compromise. [3][2][1][4][5][6]
These contraindicated medications can precipitate myasthenic crisis and respiratory failure requiring intensive‑care monitoring, underscoring the need for strict avoidance. [3][2]1

Patients with myasthenia gravis have baseline impaired neuromuscular transmission due to reduced functional nicotinic acetylcholine receptors, making them especially susceptible to agents that further disrupt transmission. [7][8][9][10]
All disease grades of myasthenia gravis warrant proactive avoidance of neuromuscular‑interfering drugs, because even mild impairment can progress to life‑threatening respiratory compromise. [3][2][1][4][5][6]

The ASCO guidelines suggest prioritizing non‑pharmacological cough control measures (e.g., humidification, positioning) before considering any medication. 2
When pharmacologic therapy is unavoidable, the ASCO recommendations advise selecting cough suppressants with no known neuromuscular effects and maintaining close clinical monitoring. 1

According to ASCO guidance, clinicians should watch for early signs of worsening muscle weakness after initiating any new drug, including dysphagia, facial weakness, and respiratory muscle fatigue. [1][4]5
If any of these symptoms emerge, immediate discontinuation or dose reduction of the offending agent is required to prevent progression to full‑blown crisis. [1][4]5

The American Society of Clinical Oncology (ASCO) guideline lists β‑blockers, intravenous magnesium, fluoroquinolone antibiotics, aminoglycoside antibiotics, and macrolide antibiotics as contraindicated in myasthenia gravis because they can exacerbate neuromuscular weakness (moderate‑quality guideline evidence) 11.

The CHEST guideline recommends dextromethorphan for cough suppression at 10–30 mg taken three to four times daily, with a maximum of 120 mg per day; the guideline does not identify myasthenia gravis as a contraindication (strong guideline recommendation) [12][13].
Dextromethorphan is not included on any ASCO or other major myasthenia gravis medication restriction lists, allowing cautious use with close monitoring (expert consensus) 11.

After initiating any new medication in a patient with myasthenia gravis, clinicians should watch for early signs of worsening weakness, including dysphagia, facial muscle weakness, respiratory muscle fatigue, and new or worsening ptosis or diplopia (clinical monitoring recommendation) 11.
If any of these symptoms appear, the new agent should be discontinued or its dose reduced promptly to prevent progression to myasthenic crisis (clinical management guidance) 11.
All grades of myasthenia gravis require proactive monitoring because even mild disease can evolve to life‑threatening respiratory compromise (guideline recommendation) 11.

Codeine or morphine derivatives may be used as alternative cough suppressants, provided they are titrated carefully to an acceptable side‑effect profile (moderate‑quality evidence) 12.
Simple linctus or glycerol‑based demulcents are suggested as first‑line non‑opioid options (moderate‑quality evidence) 12.
Combination cold medications should be avoided unless proven effective; the only over‑the‑counter products with supporting evidence are older antihistamine‑decongestant combinations (moderate‑quality evidence) 13.