Key takeaways

  • Mestinon (pyridostigmine) is a prescription drug used to treat myasthenia gravis.
  • Mestinon can cause side effects that range from mild to serious, including digestive symptoms, such as diarrhea, nausea, and vomiting.
  • Mestinon belongs to the drug class cholinesterase inhibitors and is not an immunosuppressant drug.

Mestinon is used in adults to treat myasthenia gravis. The active ingredient in Mestinon is pyridostigmine. (An active ingredient is what makes a drug work.) The drug comes in three forms:

  • extended-release oral tablet (The drug is slowly released into the body over a period of time.)
  • oral tablet
  • oral solution

Keep reading to learn about the common, mild, and serious side effects that Mestinon can cause.

Mestinon can cause certain side effects, some more common than others. These side effects may be temporary, lasting a few days to weeks. Talk with your doctor if side effects do not go away, get worse, or become too difficult to tolerate.

Mestinon’s commonly reported side effects include:

Mild side effects have been reported with Mestinon. These include:

  • muscle cramps, twitches, or weakness
  • skin rash
  • increased mucus and saliva
  • pinpoint pupils
  • excessive sweating
  • digestive side effects

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Mestinon unless your doctor recommends it.

Mestinon may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

Mestinon may cause serious side effects. The following list may not include all possible serious side effects of the drug. For more information, you can refer to Mestinon’s prescribing information.

If you develop serious side effects while taking Mestinon, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

  • cholinergic crisis, which can be life threatening

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while taking Mestinon and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

For some people, Mestinon can cause an allergic reaction.

But this side effect wasn’t reported in studies.

In general, symptoms of all allergic reaction can be mild to serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking Mestinon.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Mestinon, they may have you switch to a different treatment.

Here are answers to some commonly asked questions about Mestinon’s side effects.

Does Mestinon cause long-term side effects?

It’s unlikely. Long-term side effects weren’t reported in studies of Mestinon.

If you’re concerned about possible long-term side effects from this medication, talk with your doctor or pharmacist.

Can Mestinon cause changes in blood pressure?

Changes in blood pressure weren’t reported as a side effect in studies of Mestinon. However, the drug may be prescribed off label for the following blood pressure-related conditions:

With off-label use, a drug is prescribed for a condition it isn’t approved to treat.

Talk with your doctor if you have questions about taking Mestinon for these conditions or how the drug may affect your blood pressure when taken for myasthenia gravis.

Do side effects of Mestinon go away?

Yes, in most cases. The length of time side effects may last hasn’t been reported in Mestinon studies. But most side effects of Mestinon are expected to be temporary. They’re likely to go away soon after you start or stop taking the drug.

If you have bothersome or long lasting side effects while taking Mestinon, talk with your doctor. They can recommend ways to ease your symptoms.

There may be things you can do to help make certain Mestinon side effects more manageable. If you have ongoing, worsening, or bothersome side effects, talk with your doctor or pharmacist. They can suggest tips for managing them or recommend other available treatment options for your condition.

Digestive side effects

It isn’t known how common digestive side effects were in studies of Mestinon. Digestive side effects may cause symptoms such as:

  • diarrhea
  • nausea and vomiting
  • abdominal cramps
  • increased movement of the muscles in your digestive system

Taking a high dosage of Mestinon can increase the risk of digestive side effects from the medication.

What might help

If you have digestive side effects during Mestinon treatment, talk with your doctor. They may lower your dosage to help ease your symptoms. They can also recommend over-the-counter options, such as Pepto Bismol (bismuth subsalicylate), to help with symptom relief.

Cholinergic crisis

It isn’t known how common a cholinergic crisis was in studies of Mestinon. This condition is caused by a high level of a chemical called acetylcholine in your system.

A cholinergic crisis may cause symptoms such as muscle weakness. This can affect your lung muscles, which may cause trouble breathing. This condition can be life threatening in extreme cases.

Taking a high dosage of Mestinon can increase the risk of a cholinergic crisis. Cholinergic crisis can mimic worsening myasthenia gravis, which is important because not having a proper diagnosis can delay appropriate treatment.

What might help

Keep in mind that a cholinergic crisis may cause symptoms that are similar to worsening myasthenia gravis. (Mestinon is used to treat myasthenia gravis.)

If you have muscle weakness or trouble breathing during Mestinon treatment, tell your doctor right away. They can help you decide if your symptoms may be caused by the drug or a worsening of your condition. They can also advise you on whether it’s safe to keep taking Mestinon and whether your symptoms need treatment.

Before taking Mestinon, discuss your health history with your doctor. Mestinon may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.Mestinon- pyridostigmine bromide solution; Mestinon- pyridostigmine bromide tablet; Mestinon- pyridostigmine bromide tablet, extended release. (2020).
https://pi.bauschhealth.com/globalassets/BHC/PI/Mestinon-PI.pdf