Mestinon (pyridostigmine) is a prescription drug that’s used to treat myasthenia gravis (MG). Mestinon comes in three oral forms: a liquid solution, a tablet, and an extended-release tablet.

Mestinon is prescribed to adults with MG. To learn more about Mestinon’s uses, see the “What is Mestinon used for?” section below.

Mestinon basics

Mestinon contains the active ingredient pyridostigmine. (An active ingredient is what makes a drug work.) It belongs to a group of drugs called cholinesterase inhibitors.

Mestinon is a brand-name medication that’s also available as the generic drug pyridostigmine.

Mestinon is prescribed to treat myasthenia gravis (MG) in adults. MG is an autoimmune disease. With an autoimmune disease, your body mistakenly attacks healthy cells instead of damaged or sick ones.

With MG, your immune system damages your skeletal muscle cells. Specifically, it damages the area where muscle cells receive signals from your nerves. This damage leads to muscle weakness.

With muscle weakness, you may experience symptoms such as droopy eyelids, double vision, and fatigue (low energy). Severe MG can cause more serious symptoms, such as difficulty breathing and swallowing.

Mestinon works to treat MG by increasing the strength of the nerve signal to the damaged muscle area. It does this by preventing the breakdown of a chemical messenger called acetylcholine. With more acetylcholine present, the nerve-to-muscle signal is increased. An increased signal helps reduce muscle weakness and other symptoms of MG.

Like most drugs, Mestinon may cause mild or serious side effects. The lists below describe some of the more common side effects that Mestinon may cause. These lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you take

Your doctor or pharmacist can tell you more about the potential side effects of Mestinon. They can also suggest ways to help reduce side effects.

Mild side effects

Here’s a list of some of the mild side effects that Mestinon can cause. To learn about other mild side effects, talk with your doctor or pharmacist or read Mestinon’s prescribing information.

Mild side effects of Mestinon that have been reported include:

Mild side effects of many drugs may go away within a few days to a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.

* To learn more about this side effect, see the “Allergic reaction” section below.

Serious side effects

Serious side effects from Mestinon can occur, but they aren’t common. If you have serious side effects from Mestinon, call your doctor right away. But if you think you’re having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of Mestinon that have been reported include:

  • cholinergic crisis,* which occurs when the chemical messenger, acetylcholine, builds up in your body
  • severe allergic reaction†

* It may be difficult to tell whether you’re having a cholinergic crisis or a myasthenia gravis flare. To learn more, talk with your doctor.

† To learn more about this side effect, see the “Allergic reaction” section below.

Allergic reaction

While allergic reaction was not reported in studies of Mestinon, it can still happen. Some people may have an allergic reaction to Mestinon.

Symptoms of a mild allergic reaction can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, usually in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause difficulty breathing.

Call your doctor right away if you have an allergic reaction to Mestinon. But if you think you’re having a medical emergency, call 911 or your local emergency number.

Your doctor will recommend the dosage of Mestinon that’s right for you. Below are commonly prescribed dosages, but always follow the dosage your doctor prescribes.

Forms and strengths

Mestinon comes in three oral forms. The liquid solution and standard tablets are immediate-release (IR) drugs. This means that they release the drug into your body right away. There is also an extended-release (ER) tablet. With ER tablets, the drug is slowly released into your body over a long period of time.

Mestinon’s different forms are available in the following strengths:

  • liquid solution: 60 milligrams per 5 milliliters (60 mg/5 mL)
  • tablet: 60 mg
  • ER tablet: 180 mg

Recommended dosages

Your doctor will recommend the dosage of Mestinon that’s right for you. Below are commonly prescribed dosages, but always follow the dosage your doctor prescribes.

Your doctor may recommend that you combine different forms. For example, they may suggest that you take the liquid solution in the morning when swallowing is more difficult and then switch to the tablets later in the day. And they may recommend a combination of ER and IR forms to best manage your symptoms.

Mestinon’s maximum recommended dosage is 1,500 mg per day. This applies to all forms in any combination.

IR tablet and liquid solution

For these IR forms, the average dosage is 600 mg per day. This can consist of tablets, liquid solution, or a combination of both. Your doctor will explain how to divide this dosage into smaller doses throughout the day. You won’t take it all at once.

ER tablet

Each ER tablet has a strength of 180 mg. Your doctor may recommend that you take 1–3 tablets at a time, once or twice per day. ER doses should be separated by at least 6 hours.

Questions about taking Mestinon

Below are some common questions about taking Mestinon.

  • Can Mestinon be chewed, crushed, or split? Mestinon IR and ER tablets can likely be split. They are scored, which means they have one or two lines dividing the tablet into sections. This makes it easier to split them. But the drug manufacturer hasn’t provided information about whether Mestinon should be split, chewed, or crushed. Talk with your doctor if you have questions about splitting, chewing, or crushing the tablet. And if you have difficulty swallowing tablets, talk with your doctor about Mestinon liquid solution. You can also read this article for tips on taking tablets.
  • Should I take Mestinon with food? Mestinon can be taken with or without food. But taking Mestinon with food may help to decrease digestion-related side effects.
  • Is there a best time of day to take Mestinon? It’s best to take Mestinon on a consistent schedule each day. This helps keep a steady level of the drug in your body, which helps Mestinon work effectively.
  • What if I miss a dose of Mestinon? If you miss a dose of Mestinon, take it as soon as you remember. But if it’s almost time to take your next dose, skip the missed dose and take the next dose at its usual time. You should not take two doses at once to make up for a missed dose. Doing so could raise your risk of side effects.
  • Will I need to take Mestinon long term? Mestinon is usually taken as a long-term treatment. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely take it long term.

Overdose

Do not take more Mestinon than your doctor prescribes. Taking more than this can lead to harmful effects.

Symptoms of overdose

An overdose of Mestinon may cause a cholinergic crisis. This is a serious condition that can lead to death. Symptoms of a cholinergic crisis include:

What to do in case you take too much Mestinon

Call your doctor if you think you’ve taken too much Mestinon. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, immediately call 911 or your local emergency number. Or go to the nearest emergency room.

Below is important information you should consider before taking Mestinon.

Interactions

Taking a drug with certain medications, vaccines, foods, and other things can affect how the drug works. These effects are called interactions.

Mestinon can interact with several other medications. Before taking Mestinon, talk with your doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs you take. Also, tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

Drug interactions

Below is a list of medications that can interact with Mestinon. This list does not contain all drugs that may interact with Mestinon. If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Drug groupDrug examples
anticholinergics• atropine (Atropen)
• drugs that contain atropine, such as diphenoxylate/atropine (Lomotil)
benztropine (Cogentin)
corticosteroidsprednisone (Rayos)
methylprednisolone (Medrol)

Mestinon and alcohol

Alcohol is not known to interact with Mestinon. Talk with your doctor to determine whether it’s safe for you to consume alcohol during Mestinon treatment.

Pregnancy and breastfeeding

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

Warnings

Mestinon can sometimes cause harmful effects in people who have 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 you take Mestinon. Be sure to tell them if any of the following factors apply to you:

Find answers to some commonly asked questions about Mestinon.

Is Mestinon a controlled substance? If so, can it cause withdrawal?

Mestinon isn’t a controlled substance. This means it isn’t known to cause dependence or misuse.*

When treatment with Mestinon is stopped, you shouldn’t experience withdrawal symptoms. (Withdrawal symptoms are side effects that can occur when you stop taking a drug that your body has become dependent on.)

However, you should not stop taking Mestinon without discussing it with your doctor first. Stopping Mestinon may cause your myasthenia gravis (MG) symptoms to become worse. You could experience an MG exacerbation (flare) or crisis.

If you have questions about the potential for withdrawal symptoms if you stop taking Mestinon, talk with your doctor or pharmacist.

* With misuse, a drug is taken in a way other than how a doctor prescribes it. And with dependence, your body needs the drug to function as usual.

Does Mestinon cause constipation?

No, it doesn’t. Mestinon increases gastric motility, which is the movement of food, liquids, digestive juices, and air through your intestines. Mestinon is more likely to cause diarrhea than constipation.

In fact, the active ingredient in Mestinon, pyridostigmine, has been studied as a potential treatment for chronic constipation. (An active ingredient is what makes a drug work.)

If you experience digestive side effects while taking Mestinon, talk with your doctor.

Does Mestinon cause long-term side effects?

Long-term side effects weren’t reported in studies of Mestinon. Side effects resolved when treatment was stopped or when drugs to reverse the effects of Mestinon were given.

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

Whether you have health insurance or not, cost may be a factor when you’re considering Mestinon. What you’ll pay for Mestinon may depend on several things, such as your treatment plan and the pharmacy you use.

Here are a few things to consider regarding cost:

  • Cost information and savings coupons. You can visit Optum Perks* to get price estimates of what you’d pay for Mestinon when using coupons from the site.
  • Generic form. Mestinon is available as the generic drug pyridostigmine. Generics usually cost less than brand-name drugs. Talk with your doctor if you’d like to know whether generic pyridostigmine could be an option or you.

If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. You can also check out this article to learn more about saving money on prescriptions.

* Optum Perks is a sister site of Healthline. Optum Perks coupons cannot be used with any insurance copays or benefits.

Other drugs are available that can treat your condition. If you’d like to explore an alternative to Mestinon, talk with your doctor. They can tell you about other medications that might work well for you.

The following drugs are also prescribed to treat myasthenia gravis:

If you have questions about taking Mestinon, talk with your doctor or pharmacist. Questions you may want to ask include:

  • What do I do if I experience side effects from Mestinon?
  • When will I notice Mestinon is working?
  • Which form of Mestinon is right for me?

To learn more about Mestinon, see these articles:

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

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.