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. In some cases, treating an infection is more important than the risk of an MG exacerbation (a period when symptoms worsen, also known as a flare). In some cases, infection itself can trigger an exacerbation. Because of this, it’s essential to talk to your MG specialist before any antibiotic use.

Read on to learn which antibiotics are generally best avoided with MG and which are typically considered safer to take.

Which Antibiotics Should Be Avoided if Possible?

Some antibiotics are safer than others for people with MG. Other drugs should be avoided when possible. Doctors usually recommend staying away from the following antibiotics:

• Fluoroquinolones (such as ciprofloxacin, levofloxacin, and ofloxacin)
• Aminoglycosides (like gentamicin, tobramycin, and amikacin)
• Macrolides (including azithromycin and clarithromycin)
• Some tetracyclines (like tetracycline, doxycycline, and minocycline)

These antibiotics may cause more muscle weakness and worsen MG symptoms.

Safer Antibiotic Alternatives for People With MG

Here are some antibiotics that are typically considered safer alternatives for people with MG:

1. Penicillins

Penicillins, including amoxicillin, penicillin V, and ampicillin, are often used to treat infections. Penicillins may be used to treat infections including:

• Lung infections
• Skin infections
• Urinary tract infections (UTIs)
• Dental infections
• Strep throat
• Ear infections
• Stomach infections

They have been widely used for decades and continue to be a common choice for many bacterial infections. They work by attacking bacteria and breaking down their cell walls.

There have been some case reports in which a small number of people with MG experienced worsening of their MG symptoms after receiving an antibiotic from the penicillin class. However, such a small number of cases should not prevent penicillins from being used as a top choice for some infections. In cases where a stronger response is needed, these antibiotics can be paired with other drugs for a more effective treatment.

These antibiotics are considered lower risk for those with MG, though some people are allergic to penicillin. It’s important to tell your doctor if you’ve ever had a reaction to it.

2. Cephalosporins

Cephalosporins, such as cephalexin, cefuroxime, and ceftriaxone, are commonly prescribed for:

• Pneumonia
• Sinus infections
• Bronchitis
• Skin infections
• UTIs
• Use before surgery to prevent infections

They work similarly to penicillins and are often a good alternative for people with MG. The cephalosporin class of antibiotics are often grouped into “generations,” which can help guide providers in choosing the best cephalosporin option for fighting the infection.

These antibiotics are known for their ability to treat several tougher bacterial infections when other antibiotics fail. Additionally, some newer generations of cephalosporins are effective against antibiotic-resistant bacteria, making them even more important in modern medicine.

If you have a penicillin allergy, tell your doctor before taking cephalosporins, since they’re close relatives of penicillins.

3. Clindamycin

Clindamycin is usually prescribed for:

• Dental infections
• Bone infections
• Skin infections (including methicillin-resistant Staphylococcus aureus, also known as MRSA)
• Stomach infections
• Infections inside the pelvis
• Acne

Clindamycin works by stopping bacteria from making the proteins they need to grow. This antibiotic is an option for people who can’t take penicillin. While generally safer for those with MG, clindamycin can sometimes cause stomach problems, including a risk of Clostridioides difficile (C. diff) infections.

Clindamycin is often given by mouth or intravenously (through an IV), depending on the severity of the infection. Clindamycin can reach deep into bone tissue. This makes it a good medicine for bone infections, which can be hard to treat with other antibiotics.

4. Vancomycin

Vancomycin is a strong antibiotic that treats severe infections, including MRSA infections and blood infections. It may also be used before surgery to prevent infections, especially in surgeries involving the heart or bones.

While vancomycin is considered safer for those with MG, it can have side effects, including kidney problems and reactions from the IV infusion. Vancomycin’s strength against antibiotic-resistant bacteria makes it an essential antibiotic for hospital settings. With growing antibiotic resistance (bacteria that won’t respond well to antibiotics), vancomycin remains one of the few reliable options for treating life-threatening bacterial infections.

5. Trimethoprim-Sulfamethoxazole

This combination antibiotic, sold under the brand names Bactrim and Septra, is often used for:

• UTIs
• Lung infections
• MRSA-related skin infections
• Prevention of pneumonia for people with weakened immune systems (like those with HIV/AIDS)
• Infections in the intestines

Trimethoprim-sulfamethoxazole is usually well tolerated in people with MG, but some people may have allergic reactions or stomach issues. Additionally, this antibiotic is commonly used to treat traveler’s diarrhea, making it useful for people traveling to regions with poor sanitation. Research has also shown that the combination drug can be effective in treating infections caused by drug-resistant bacteria.

6. Nitrofurantoin

Nitrofurantoin, sold under the brand names Macrobid and Macrodantin, is a common antibiotic for UTIs. Some doctors even prescribe it to prevent UTIs in those who get them often. Because it mainly works in the urinary tract, it has less effect on the rest of the body. This makes it a generally safer option for people with MG. It works by damaging bacterial DNA, stopping bacteria from multiplying. It works well against bacteria like E. coli, a common cause of UTIs.

Some people may have stomach upset or lung-related side effects if they use nitrofurantoin for a long time. Nitrofurantoin is unique because it concentrates almost exclusively in the urinary tract, reducing its effect or possible consequences on other areas of the body.

Always Talk to Your Doctor About the Best Option

Even though these antibiotics are considered safer for people with MG, every person is different. What works well for one person may not be right for another. That’s why working with your doctor is the best way to find the right antibiotic while managing MG symptoms.

Some infections require stronger antibiotics, and in some cases, there may be no alternative to an MG-risk antibiotic. In some cases, close monitoring by a doctor is necessary. Side effects may be managed with other medications or dose adjustments.

If you have MG and need an antibiotic, always check with your neurologist or MG specialist first. They can help you weigh the risks and benefits and choose the safest option for your situation.

Talk With Others Who Understand

MGTeam is the social network for people with myasthenia gravis and their loved ones. On MGTeam, members come together to ask questions, give advice, and share their stories with others who understand life with myasthenia gravis.

Have you used antibiotics since you were diagnosed with MG? Which have worked well for you, and which have caused problems? Share your experience in the comments below, or start a conversation by posting on your Activities page.