Myasthenia gravis (MG) is an autoimmune neuromuscular disorder that affects an estimated 14 to 20 patients per 100,000 in the United States. Most patients with MG have autoantibodies against acetylcholine receptors (AChRs), which disrupt neuromuscular transmission through downregulation, destruction, blocking of AChRs or disrupting receptors in the postsynaptic membrane.

Several medications may worsen MG or precipitate myasthenic crisis, however, incidence is difficult to describe as literature is largely limited to case reports and there is often presence of other confounding factors. There are two proposed mechanisms for medications to cause or exacerbate MG:

1. Eliciting an autoimmune reaction against neuromuscular junction 
2. Interference with neuromuscular transmission

Several medications commonly used in the emergency department are known to impair neuromuscular transmission and may induce or worsen MG. The following medications should be avoided, or used with extreme caution in patients with MG*: 

*This list contains several common medications utilized in the emergency department, but is not an all-inclusive list of medications that may exacerbate MG. Please refer to the reference section for additional information.

References

1. Howard JF. Clinical Overview of Myasthenia Gravis [Internet]. Westborough, MA: Myasthenia Gravis Foundation of America. 2015 June [cited 2024 May 8]. Available from: https://myasthenia.org/Professionals/Clinical-Overview-of-MG#:~:text=other%20autoimmune%20disorders.-,Epidemiology,cases%20in%20the%20United%20States
2. Dresser L, Wlodarski R, Rezania K, Soliven B et al. Myasthenia gravis: epidemiology, pathophysiology, and clinical manifestations. J Clin Med. 2021; 10 (11): 2235.
3. Sheikh S, Alvi U, Soliven, Rezania K. Drugs that induce or cause deterioration of myasthenia gravis: an update. J Clin Med. 2021; 10 (7): 1537. 
4. Narayanaswami P, Sanders DB, Wolfe G, Benatar M, Cea G, Evoli A et al. International consensus guidance for management of myasthenia gravis: 2020 update. Neurology. 2021; 96: 114-122.