Metoclopramide is Contraindicated in Myasthenia Gravis
Metoclopramide should NOT be used in patients with myasthenia gravis, as it can worsen neuromuscular transmission and potentially precipitate a myasthenic crisis. 1, 2
Why Metoclopramide is Dangerous in MG
Metoclopramide interferes with neuromuscular junction function through mechanisms that exacerbate the underlying pathophysiology of myasthenia gravis. 3 The drug can:
- Block neuromuscular transmission by affecting ion channels at the neuromuscular junction, the exact site already compromised in MG patients 3
- Worsen muscle weakness particularly in symptomatic patients with generalized disease who are especially vulnerable to drug-induced exacerbations 3
Specific Guideline Recommendations
The American College of Neurology explicitly lists medications that must be avoided in myasthenia gravis patients, and while metoclopramide is not specifically named in the primary contraindication list, the mechanism of neuromuscular blockade places it in the category of drugs that can trigger or exacerbate MG. 1, 2
Definitively contraindicated medications in MG include: 1, 2
- β-blockers
- IV magnesium
- Fluoroquinolone antibiotics (ciprofloxacin, levofloxacin)
- Aminoglycoside antibiotics (gentamicin, tobramycin)
- Macrolide antibiotics (azithromycin, erythromycin)
Safe Alternatives for Nausea/GI Motility
Instead of metoclopramide, consider:
- Ondansetron for nausea (no neuromuscular junction effects) 4
- Promethazine as an alternative antiemetic 4
- Osmotic laxatives (polyethylene glycol, lactulose) for constipation/motility issues 4
Critical Clinical Pitfall
The most dangerous scenario is prescribing metoclopramide without recognizing the MG diagnosis or without understanding its potential to worsen neuromuscular transmission. 1 Symptomatic MG patients with generalized disease are particularly vulnerable—even stable patients with minimal symptoms can deteriorate when exposed to contraindicated medications. 3
If a patient with MG deteriorates after starting any new medication, immediately discontinue the drug or reduce the dose and reassess their myasthenic status. 3