Part 4 · Crisis, care & the future
Drugs that can worsen MG
Some medicines can weaken the nerve-to-muscle signal or set off the immune attack in MG. Press play to light each site at the junction, then search the checker for a drug's evidence badge and its US label wording.
Schematic, not to scale. The site shown for each drug follows what its label or the sources read say; where they name no site, the drawing says so instead of guessing. The signal meter is illustrative, not measured. 302,490
The checker
Label wording is quoted from the US prescribing information cited, read on DailyMed, with omissions marked "…". Badges describe the strongest published statement found, not how often harm happens. The 2020 international consensus update has a table of drugs to avoid or use with caution; it is cited here but not quoted, because its wording could not be read in the version accessed. 381
All entries
| Drug or class | Badge | Site at the junction | Sheikh 2021 rating or summary | Main source |
|---|
How big is the risk in practice?
Antibiotic courses
2.4% vs 1.3%Exacerbation followed 2.4% of ciprofloxacin, 1.6% of levofloxacin and 1.5% of azithromycin courses, against 1.3% of amoxicillin courses (p = 0.68). Infection itself was a confounder in 88.2% of these exacerbations. 527
Overridden alerts
12.7%of 55 hospital encounters where an MG drug alert was overridden were followed by an exacerbation, all after IV magnesium or IV labetalol; in 5 of 7 events another risk factor was present. 422
A national database
89.6%of 14,459 French people with MG received a "contraindicated" drug during follow-up, and exposure was not linked to ICU admission for MG (HR 1.04). For statins, long-term mortality benefit likely outweighs the short-term MG risk, the authors suggest. 499
Usually considered safe
One review lists cephalosporins, sulfa drugs, clindamycin, tetracyclines, polymyxin B and nitrofurantoin as antibiotics that can be given safely in MG. 490
Starting steroids and checkpoint inhibitors
Steroid start Label warning
42% of 55 people given prednisone 40-80 mg worsened within 4 weeks, more often with older age, severe bulbar symptoms and more severe MG; published rates range from 25% to 75%, mostly in the first 2 weeks, and 8.6% severe worsening needing ventilation in one table. The prednisone label warns that anticholinesterases together with corticosteroids may produce severe weakness in MG. Giving IVIG first was followed by worsening in 2.2% of 45 patients. The consensus says it may be reasonable to let PLEX or IVIG act for several days before starting steroids in impending crisis. Doses for a person are set by the treating clinician. 29,102,157,302,476,490
Checkpoint inhibitors Label warning
MG appeared in 0.12% (12 of 9,869) on nivolumab and 0.24% (14 of 5,898) in another study. In 65 cases, median onset was 4 weeks; 37% also had myositis, 45% respiratory failure, and 38% died (23% from MG); IVIG or PLEX first did better than steroids alone (95% vs 63% improved). In-hospital mortality of the myositis-myocarditis-MG overlap is close to 40%. The 2020 consensus: existing MG is not an absolute contraindication, and avoiding anti-CTLA-4 plus anti-PD-1/PD-L1 combinations may be prudent. 182,381,471,490,509