Maybe you have pneumonia. Perhaps you have conjunctivitis (pink eye), or you’re traveling internationally and need treatment for malaria prevention. In these situations, your doctor may have recommended you take the antibiotic doxycycline. But if you have the autoimmune disease myasthenia gravis (MG), you may wonder if the medication is safe for you.

The short answer is, it might be, but you should talk with your doctor first.

If you have MG, your body’s immune system makes proteins called autoantibodies that interfere with the movement of a brain chemical called acetylcholine. Acetylcholine helps your muscles contract (activate). When autoantibodies block acetylcholine receptors (AChRs) in your nervous system, your muscles have difficulty contracting properly. Consequently, they weaken and tire easily.

Some medications, including certain antibiotics, also interfere with your acetylcholine. As a result, there’s a chance they may make your symptoms worse. Keep reading to learn about doxycycline and how it may affect you if you’re diagnosed with MG.

What Can Doxycycline Treat?

Doxycycline is an antibiotic that belongs to a family of medications called tetracyclines. It works by stopping the growth and spread of bacteria, and it also can help reduce inflammation. Doctors prescribe doxycycline to treat a wide range of bacterial infections, including:

• Acne
• Eye infections
• Gum disease
• Infections caused by lice, mites, or ticks
• Malaria
• Respiratory infections like pneumonia
• Rosacea, a skin condition that causes discoloration and bumps
• Sexually transmitted infections, such as chlamydia, gonorrhea, and syphilis
• Urinary tract infections

Like many medications, doxycycline can cause side effects. Some common ones include nausea, vomiting, diarrhea, loss of appetite, and an upset stomach. It may also lead to darkened skin, itching, and vaginal yeast infections.

Who Should Avoid Doxycycline?

Doxycycline is generally safe for most adults and children over age 12. But it isn’t for everyone. You should not take doxycycline if you’re allergic to other tetracycline medications or if you’re pregnant or breastfeeding.

Additionally, before starting on doxycycline, tell your doctor if you’re also taking:

• Isotretinoin, a medication for severe acne
• Seizure medication
• Blood thinners like warfarin

Be sure to let your doctor know if you have or have ever had:

• Asthma
• Intracranial hypertension (high pressure in your skull)
• Inflammation of the esophagus (food pipe)
• Kidney disease
• Liver disease
• Lupus (an autoimmune condition that can affect the skin, joints, and organs)
• A sulfite allergy

How Does Doxycycline Affect Myasthenia Gravis?

If you have myasthenia gravis, the most important thing to know about doxycycline is how it affects acetylcholine — the chemical that helps your muscles contract. MG weakens muscles by blocking acetylcholine from reaching AChRs at the neuromuscular junction — the connection point between nerves and muscles where signals trigger movement. Doxycycline may also interfere with acetylcholine signals, which could make muscle weakness worse.

However, some research shows that tetracyclines like doxycycline typically have little to no effect on myasthenia gravis symptoms. In fact, compared to other types of antibiotics — including fluoroquinolones like ciprofloxacin or macrolides like erythromycin — doxycycline is less likely to worsen MG symptoms. If it does cause changes, they may be mild or go away once you stop taking the antibiotic.

That said, there is a small risk of a rare condition called drug-induced myasthenia. In these cases, certain antibiotics, including tetracyclines like doxycycline, can trigger temporary muscle weakness that mimics MG. While this is uncommon, it’s still important to be aware of the possibility.

If your doctor prescribes doxycycline, pay close attention to any side effects. Call your doctor immediately if you notice any worsening of your muscle weakness, fatigue, or other MG symptoms.

What Are the Symptoms of Drug-Induced Myasthenia?

In rare cases, certain medications — including doxycycline and the autoimmune drug penicillamine — can trigger drug-induced myasthenia. This condition causes symptoms that closely resemble myasthenia gravis, making it feel like your MG has worsened.

If you develop drug-induced myasthenia, you may experience:

• Difficulty speaking
• Difficulty swallowing
• Fatigue (extreme tiredness that doesn’t improve with sleep)
• Muscle weakness (especially around your eyes, face, arms, and legs)
• Respiratory (breathing) problems

If you notice any of these signs, tell your doctor right away. They may adjust your treatment, stop doxycycline, or switch you to a different medication. In rare cases, additional treatments may be needed to help manage temporary symptoms.

Why Should You Talk to Your Doctor About All Medications?

As an autoimmune disease, myasthenia gravis can make you sensitive to certain medications that could trigger symptoms to flare up. This includes both prescription and over-the-counter drugs. That’s why keeping your healthcare team informed about any new medication is essential.

Your healthcare provider can help you weigh the risks and benefits of taking a new prescription — such as doxycycline for an infection. In some cases, doxycycline may still be the best option, even if it temporarily worsens your MG symptoms. Your doctor might adjust your dose, monitor your symptoms closely, or recommend a safer alternative. A pharmacist can also check for interactions with any immunosuppressive medications you take.

Before starting a new medication, always talk to your doctor or pharmacist. Your doctor can assess the medical risks, while your pharmacist can check for drug interactions with your current medications. A well-informed healthcare team can help you get the treatment you need while minimizing potential risks.

Find Your Team

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 experiences with others who understand life with myasthenia gravis.

Have you ever taken doxycycline? Did it make your muscle weakness worse? Share your story in the comments below or start a conversation by posting on your Activities page.