Pyridostigmine

What is pyridostigmine?

Pyridostigmine is a medicine that is commonly used to improve muscle strength in individuals with neuromuscular disorders. Pyridostigmine increases the amount of acetylcholine (a neurotransmitter that supports muscle contraction) in the body, which helps alleviate symptoms such as muscle weakness and fatigue. It is most often used in conditions such as myasthenia gravis (MG) and congenital myasthenic syndrome (CMS).

You may hear pyridostigmine called by one of its brand names, Mestinon. It is available as a regular tablet, a slow-release tablet, as well as an oral liquid. Not all pharmacies carry the oral liquid. Double check with your pharmacy that it is available.

How does pyridostigmine work?

Pyridostigmine works by blocking an enzyme (acetylcholinesterase) that breaks down acetylcholine. Acetylcholine is an important chemical messenger that helps nerves and muscles communicate. Pyridostigmine improves muscle function and strength, making it a valuable treatment option for managing neuromuscular symptoms. 

Before giving pyridostigmine to your child

Talk with your child’s health-care provider if your child has:

• any allergies
• any respiratory conditions: pyridostigmine affects muscle function, including respiratory muscles; children with a history of breathing problems, asthma or lung infections may need additional monitoring
• any issues passing urine (peeing) or has bowel block (difficulty passing stools) 

How to give pyridostigmine to your child

Administering pyridostigmine properly is crucial for its effectiveness and minimizing side effects.

• Follow the prescribed dosage and schedule: Pyridostigmine is often prescribed in multiple doses throughout the day to maintain consistent levels in the body. Your child’s health-care provider may adjust the timing to help manage symptoms effectively. Extended-release forms of pyridostigmine require less frequent dosing but must be timed carefully, as they release medication gradually.
• Take with food (if needed): To reduce the chance of stomach upset, give pyridostigmine with food or milk unless directed otherwise by your child’s health-care provider. Taking it with food can help manage common side effects such as nausea or stomach discomfort.
• Giving tablets: Tablets should ideally be swallowed whole, with a glass of water. For young children or those who have difficulty swallowing, speak to your pharmacist about options. Pyridostigmine may be available in liquid form or a crushable tablet, depending on the prescription.
• Never crush or chew extended-release tablets, as this can cause the medication to release all at once, increasing the risk of side effects. 
• Monitor for side effects: Observe your child for potential side effects, such as increased saliva, sweating or mild nausea, which are common when starting pyridostigmine. If you notice severe symptoms, such as extreme muscle weakness, breathing difficulties or an irregular heartbeat, contact your child's health-care provider immediately. 

What should you do if your child misses a dose of pyridostigmine?

• Give the missed as soon as you remember.
• If it is almost time for the next dose, skip the missed dose. Give the next dose at the regular time.
• Do not give two doses at once to make up for one missed dose. This can lead to overdose symptoms, such as excessive muscle weakness or cramps.

What are the possible side effects of pyridostigmine?

While pyridostigmine is generally considered a safe and effective medication, it is important to remember that, like all medications, it is not completely free from possible side effects.

Common side effects: These typically do not require immediate attention

These side effects are generally mild and may lessen as your child’s body adjusts to pyridostigmine. However, if they continue or become bothersome, report them to your child’s health-care provider:

• Diarrhea: Often occurs at the start of treatment and may improve over time.
• Increased saliva: Some children may experience excessive saliva production (drooling).
• Increased sweating: Pyridostigmine can cause increased sweating, which may be managed with dose adjustments.
• Nausea: Mild nausea may occur initially and usually improves as the body adapts to the medication.
• Increased urge to urinate (pee)

Serious side effects: Contact your child’s health-care provider right away if your child experiences any of the following:

• Skin rash, itching, hives or swelling of the face, lips or tongue
• Difficulty breathing, wheezing, tightness in chest or shortness of breath
• Difficulty swallowing or talking
• Sudden blurred vision or double vision, or changes in appearance of pupils
• Muscle cramps, spasms or twitching
• Slow or irregular heartbeat
• Severe abdominal discomfort or pain
• Unusual weakness or fatigue that is new or worse than before
• Upset stomach or throwing up
• Confusion
• Sweating a lot

What safety measures should you take when your child is using pyridostigmine?

There are some medicines that should not be taken together with pyridostigmine, or, in some cases, the dose of pyridostigmine or the other medicine may need to be adjusted. It is important that you tell your child’s health-care provider if your child takes any other medications (prescription, over the counter or herbal), including:

• a group of antibiotics called aminoglycosides (e.g., gentamicin, tobramycin, amikacin)
• some types of general anesthetics used in major surgeries
• certain heart medications including beta blocks (e.g., propranolol) and dipyridamole
• medications that can cause the heart to beat slower
• medications used to relax the muscles during surgeries (e.g., succinylcholine)

If your child is undergoing any kind of surgery, whether they will be put to sleep (anesthetized) or kept awake, ensure the health-care team knows that your child is taking pyridostigmine.

Note: This list may not cover all interactions. Always inform your child’s health-care provider of all medications, herbs or supplements being used.

What to monitor after starting pyridostigmine in your child

After your child begins the medication, their health-care provider will:

• regularly check for any side effects and track symptoms to assess how your child is responding to the treatment
• evaluate your child periodically to determine whether the current dosage is effective. Depending on changes in symptoms, your child’s health-care provider may modify the pyridostigmine dose or suggest additional therapies to enhance muscle strength.

What other important information should you know about pyridostigmine?

• Keep a list of all medications your child is on and show the list to your child’s health-care provider.
• Do not share your child’s medicine with others and do not give anyone else’s medicine to your child.
• Make sure you always have enough pyridostigmine to last through weekends, holidays and vacations. Call your pharmacy at least two days before your child runs out of medicine to order refills.
• Keep all appointments at the clinic or health-care provider’s office so that they can check your child's reaction to pyridostigmine.
• Keep pyridostigmine at room temperature in a cool, dry place away from sunlight. Do NOT store it in the bathroom or kitchen.
• Do not keep any medicines that are out of date. Check with your pharmacist about the best way to throw away outdated or leftover medicines.

At SickKids

SickKids has a specialized neuromuscular clinic that focuses on myasthenia gravis, congenital myasthenic syndrome and similar conditions. Located within the Neurology Department, the clinic is staffed by a neurologist, nurse practitioner and experienced technicians who are dedicated to caring for children with neuromuscular disorders. Our clinic visits range from simple follow-ups to more specialized procedures, such as nerve conduction studies and electromyography. Additionally, we offer access to a professional social worker who can provide support for both you and your child and connect you with relevant support groups if needed.

To learn more about the Neuromuscular Program at SickKids, visit https://www.sickkids.ca/en/care-services/clinical-departments/neurology/neuromuscular-program/.

Keep pyridostigmine out of your child’s sight and reach and locked up in a safe place. If your child takes too much pyridostigmine, call your local Poison Information Centre at one of these numbers. These calls are free. 

• Call 1-844 POISON-X, or 1-844-764-7669, from anywhere in Canada except Quebec.
• Call 1-800-463-5060 if you live in Quebec.