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If you have myasthenia gravis (MG), taking antibiotics can be tricky. Some antibiotics may make MG symptoms worse, causing muscle weakness, trouble breathing, or a myasthenic crisis — a medical emergency.
But it’s not always possible to avoid antibiotics, especially if you have a serious infection. Infection itself can trigger a myasthenia gravis flare, so treatment of a significant infection shouldn’t be delayed unnecessarily.
Be sure to tell any healthcare provider prescribing an antibiotic that you have myasthenia gravis. Your neurologist may need to be involved if the antibiotic carries a myasthenia gravis risk, your symptoms aren’t stable, or choosing a treatment is complicated.
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Read on to learn which antibiotics are generally best avoided with myasthenia gravis and which are typically considered safer to take.
Myasthenia gravis is an autoimmune disease, meaning the immune system attacks healthy tissue. It affects the way nerves send signals to muscles. Certain antibiotics can interfere with these signals and cause new or worsening muscle weakness.
Symptoms may include drooping eyelids, double vision, trouble chewing or swallowing, weak arms or legs, or trouble breathing. However, the infection itself can also cause a myasthenia gravis exacerbation (flare), making it hard to tell which is responsible.
— An MGteam member
Seek emergency care for severe trouble breathing or swallowing or rapidly worsening weakness. These may be signs of a myasthenic crisis.
“Safer” doesn’t mean an antibiotic is risk-free or right for every infection. The best antibiotic depends on the infection, the bacteria causing it, allergies, other medications, and your overall health.
Here are some antibiotics that are typically considered safer alternatives for people with myasthenia gravis:
These are examples only. An antibiotic that’s right for one infection may not work for another. Your doctor may also use test results, such as a urine or blood culture, to help choose the right medication.
Penicillins, including amoxicillin, penicillin V, and ampicillin, are often used to treat infections. Penicillins may be used to treat infections including:
Penicillins have been widely used for decades and continue to be a common choice for many bacterial infections. They work by preventing bacteria from building their cell walls.
There have been some case reports of worsening myasthenia gravis symptoms after penicillins.
However, these reports are uncommon. Current evidence doesn’t suggest that people with myasthenia gravis generally need to avoid penicillins, and they’re often considered a lower-risk choice.
Some people are allergic to penicillin. Tell your doctor if you’ve ever had a reaction to it.
Cephalosporins, such as cephalexin, cefuroxime, and ceftriaxone, may treat:
Some cephalosporins are also used before surgery to prevent infections.
They work similarly to penicillins and are often a good alternative for people with myasthenia gravis.
Different cephalosporins work against different bacteria, giving doctors several options depending on the infection.
If you have a penicillin allergy, tell your doctor before taking cephalosporins, since they’re close relatives of penicillins.
Clindamycin may be used for dental, bone, skin, and other bacterial infections. It works by stopping bacteria from making proteins they need to grow.
Clindamycin is generally considered lower risk for worsening myasthenia gravis. It may also be an option for some people who can’t take penicillin.
However, clindamycin can cause stomach problems. One important risk is diarrhea caused by Clostridioides difficile (C. diff), which can sometimes be serious.
Vancomycin is given through a vein to treat severe infections, including MRSA (a type of antibiotic-resistant staph bacteria) infections and some blood infections.
Vancomycin is often viewed as lower risk for myasthenia gravis than fluoroquinolones or aminoglycosides. However, one published case report linked vancomycin with a myasthenic crisis.
A single case report can’t prove the antibiotic caused the crisis. Infection or other factors may have contributed.
This limited evidence doesn’t mean people with myasthenia gravis routinely need to avoid vancomycin. However, new or worsening weakness during treatment should be reported.
Vancomycin can also cause side effects, including kidney problems and reactions related to IV infusions.
Trimethoprim-sulfamethoxazole is a combination antibiotic that may treat UTIs, some lung infections, and MRSA-related skin infections.
It’s generally considered a lower-risk antibiotic for myasthenia gravis because clinical reports haven’t established it as a common cause of myasthenia gravis worsening.
However, some people may have allergic reactions or stomach problems. It can also interact with certain medications and may not be suitable for people with some kidney problems.
Nitrofurantoin is a common antibiotic for UTIs. Because it becomes concentrated in the urinary tract, it’s mainly used for bladder infections.
It’s generally considered a lower-risk option for myasthenia gravis when appropriate. However, one case report linked nitrofurantoin to ocular myasthenia, which causes weakness in the muscles controlling the eyes and eyelids.
This is very limited evidence and doesn’t establish nitrofurantoin as a medication that people with myasthenia gravis generally need to avoid.
Some people may have stomach upset. Rare but serious lung, liver, or nerve problems can also occur, particularly with longer-term use.
Even antibiotics considered safer for people with myasthenia gravis aren’t right for everyone.
Tell the clinician prescribing your antibiotic that you have myasthenia gravis. Ask whether the medication is known to worsen myasthenia gravis and whether a lower-risk antibiotic would treat your infection just as well.
— An MGteam member
Some infections require antibiotics that carry a myasthenia gravis risk. In these cases, your healthcare team may decide that treating the infection is vital and monitor you closely for changes in muscle strength, swallowing, or breathing.
A 2025 study looked at 918 treatment episodes involving ciprofloxacin, levofloxacin, or azithromycin in people with myasthenia gravis. A flare occurred in 8 of 339 treatment episodes involving ciprofloxacin, 3 of 187 for levofloxacin, and 6 of 392 for azithromycin — 17 of 918 episodes, or about 1.9 percent overall. Some of these flares were serious.
This doesn’t mean these antibiotics are harmless. Serious worsening has been reported, and fluoroquinolones carry a boxed warning from the U.S. Food and Drug Administration (FDA) about worsening MG. The findings suggest worsening occurs in a minority of treatment episodes and that risks and benefits should be considered for each person.
Ask your neurologist or myasthenia gravis specialist for advice if your symptoms aren’t well controlled, you’ve previously reacted to an antibiotic, the proposed antibiotic is known to worsen myasthenia gravis, or treatment choices are limited.
Don’t stop an antibiotic simply because you feel better, but follow the medication’s instructions about serious side effects and when to seek urgent care. An untreated infection can also worsen myasthenia gravis. Your neurologist or myasthenia gravis specialist can help you weigh the risks and benefits and choose the safest option for your situation.
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I can’t even take those meds you say are safe. I’m allergic to some & go into a flare from others. Penicillin is the only thing I have not had issues with.
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