Drugs that May Worsen MG

Important Statement

Many different drugs have been associated with worsening myasthenia gravis (MG). However, these drug associations do not necessarily mean that a patient with MG should not be prescribed these medications because in many instances the reports are very rare and in some instances, they might only be a “chance” association (i.e. not causal). Also, some of these drugs may be necessary for a patient’s treatment. Therefore, some of these drugs should not necessarily be considered “off limits” for MG patients. Careful thought needs to go into decisions about a prescription. It is advisable that patients and physicians recognize and discuss the possibility that a particular drug might worsen the patient’s MG. They should also consider, when appropriate, the pros and cons of an alternative treatment, if available.  It is important that the patient notify his or her physicians if the symptoms of MG worsen after starting any new medication. We are only listing the more common prescription drugs with the strongest evidence suggesting an association with worsening MG.

For a list of our drugs that may worsen MG, please click here.


It is generally believed that vaccinations (e.g. influenza) are safe for patients with MG, with a major exception below. The evidence suggests that vaccine-related worsening of MG is rare. Most MG specialists believe the benefits of immunization outweigh any small risk related to possible transient worsening of MG symptoms.

Exception: If you are taking immunosuppressive medication, such as prednisone, azathioprine or mycophenolate, it is usually recommended that you avoid live, attenuated vaccines. Examples of live, attenuated vaccines include the shingles vaccine and the nasal spray form of the influenza vaccine (the influenza injection is inactivated and thus not alive, so it is much safer in immunosuppressed patients). It is important that you discuss this with any doctor when considering a vaccine. If you are not sure, ask your doctor if you are taking immunosuppressive drugs and, if so, whether the vaccine is safe for you. Of note, most vaccines are inactivate (e.g. dead), but few vaccines are alive and attenuated (i.e. the pathogen is alive but not very virulent and thus immunizes the patient without causing the disease). As the live, attenuated vaccines carry higher risk for those who are immunosuppressed, this technicality is important and is always worth consideration.

Shingrix Vaccine: Shingrix is a new non-live vaccine against varicella zoster, the virus that causes Shingles and Chicken Pox. Shingles occurs most often in patients with compromised immune system function. Many of the treatments for myasthenia gravis increase the risk of developing Shingles. The Shingrix vaccine has been shown extremely effective in two large clinical trials of adults over the age of 50. The vaccine is now recommended by the Centers for Disease Control (CDC) for all adults over age 50. Unlike the previous shingles vaccine, Shingrix does not have a live virus component. Shingrix is likely safe for patients with reduced immune system function, like MG patients taking immunosuppressant medications. Studies are underway to evaluate efficacy of Shingrix in patients with reduced immune system function. MG patients over age 50 should discuss the risks and benefits of Shingrix with their primary care doctor and neurologist.