Mestinon (pyridostigmine) is a prescription drug used to treat myasthenia gravis. Mestinon can cause side effects that range from mild to serious. Examples include digestive symptoms, such as diarrhea, nausea, and vomiting.

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
  • oral tablet
  • oral solution

Keep reading to learn about the common, mild, and serious side effects that Mestinon can cause. For a general overview of the drug, including details about its uses, see this article.

* “Extended release” means the drug is slowly released into your body over a period of time.

Some people may experience mild to serious side effects during Mestinon treatment. Examples of the drug’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

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*
  • mild allergic reaction*†

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.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Mestinon, but this side effect wasn’t reported in studies.

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

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.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Mestinon, but this side effect wasn’t reported in studies.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Mestinon, visit MedWatch.

Get answers to some frequently 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:

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.

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

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.

Learn more about some of the side effects Mestinon may cause.

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.

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.

Allergic reaction

Like most drugs, Mestinon can cause an allergic reaction in some people. But this side effect wasn’t reported in studies. Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin (usually in your eyelids, lips, hands, or feet)
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

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. Examples include:

  • an oral antihistamine, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Mestinon, they’ll decide if you should continue taking it.

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.

Keeping track of side effects

During your Mestinon treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Mestinon affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before starting Mestinon.

Warnings

Mestinon can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Mestinon is a good treatment option for you.

Talk with your doctor about your health history before starting this medication. Be sure to tell them if any of the following factors apply to you:

Alcohol and Mestinon

There are no known interactions between alcohol and Mestinon. If you have questions about consuming alcohol during treatment with this drug, talk with your doctor or pharmacist.

Pregnancy and breastfeeding with Mestinon

There is limited information about the safety of Mestinon use during pregnancy or while breastfeeding.

Pregnancy

It’s not known whether it’s safe to take Mestinon during pregnancy. If you’re pregnant or planning to become pregnant, talk with your doctor before starting treatment with this medication.

Breastfeeding

It isn’t known whether Mestinon is safe to take while breastfeeding. If you’re breastfeeding or planning to do so, talk with your doctor before starting this medication.

Like most drugs, Mestinon can cause a number of side effects that range from mild to serious. But most are temporary and go away after a few days to weeks. If you have questions about side effects that Mestinon can cause, talk with your doctor. Examples of questions to help get you started include:

  • How do the side effects of Mestinon compare with those of other treatments for my condition?
  • Does my dosage of Mestinon impact my risk of side effects?
  • Do I have any medical conditions that increase my risk of side effects from Mestinon?

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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.