Mestinon (Pyridostigmine Bromide)
Acetylcholinesterase inhibitor for myasthenia gravis and intestinal atony
Quick facts about Mestinon
Key takeaways about Mestinon
- Primary treatment for myasthenia gravis: Mestinon improves muscle strength by preventing the breakdown of acetylcholine at the neuromuscular junction
- Short-acting medication: Each dose lasts 3–6 hours, requiring multiple daily doses (typically 3–6 times per day) for continuous symptom control
- Take with plenty of water: Mestinon should be taken with ample water and the dose must be individually determined by your physician
- Never exceed prescribed dose: Overdose can cause a cholinergic crisis with respiratory failure, which is a medical emergency
- Important drug interactions: Several medications can alter Mestinon's effectiveness, including immunosuppressants, aminoglycoside antibiotics, and neuromuscular blocking agents
What Is Mestinon and What Is It Used For?
Mestinon (pyridostigmine bromide) is an acetylcholinesterase inhibitor that prevents the breakdown of the neurotransmitter acetylcholine, allowing nerve impulses to more effectively stimulate muscles. It is primarily used to treat myasthenia gravis and intestinal atony (reduced bowel motility).
Mestinon belongs to a class of medications known as acetylcholinesterase inhibitors, also called anticholinesterase agents. The active substance, pyridostigmine bromide, works by blocking the enzyme acetylcholinesterase, which normally breaks down the neurotransmitter acetylcholine at the neuromuscular junction. By inhibiting this enzyme, Mestinon allows acetylcholine to accumulate and exert a stronger and more prolonged effect on the muscle receptors, thereby improving neuromuscular transmission and restoring muscle function.
The primary indication for Mestinon is myasthenia gravis, a chronic autoimmune neuromuscular disorder in which antibodies attack acetylcholine receptors at the neuromuscular junction. This results in progressive muscle weakness and fatigue that worsens with activity and improves with rest. Myasthenia gravis can affect any voluntary muscle, but most commonly impacts the muscles controlling eye movements, facial expressions, chewing, swallowing, and limb movements. The condition affects approximately 15 to 20 per 100,000 individuals worldwide, according to epidemiological data from the American Academy of Neurology (AAN).
Mestinon is also indicated for intestinal atony, a condition characterized by reduced or absent motility of the intestinal tract. In this context, pyridostigmine stimulates smooth muscle contractions in the gastrointestinal tract through its cholinergic action, promoting normal bowel movements. This application is particularly relevant in post-operative settings where bowel function may be temporarily impaired.
It is important to understand that Mestinon does not cure myasthenia gravis but rather provides symptomatic relief by improving muscle strength and function. The medication is often used alongside other treatments such as immunosuppressive therapies, which address the underlying autoimmune process. According to the European Federation of Neurological Societies (EFNS) and the European Neurological Society (ENS) guidelines, pyridostigmine is considered the first-line symptomatic treatment for myasthenia gravis.
In healthy neuromuscular transmission, nerve impulses trigger the release of acetylcholine, which binds to receptors on muscle cells to cause contraction. In myasthenia gravis, antibodies destroy many of these receptors. Pyridostigmine compensates by preventing the rapid breakdown of acetylcholine, so the remaining receptors have more opportunity to be activated, resulting in improved muscle contraction.
What Should You Know Before Taking Mestinon?
Before starting Mestinon, inform your physician about all existing medical conditions, particularly respiratory diseases, heart conditions, gastrointestinal disorders, epilepsy, and kidney problems. Mestinon must not be used if you have mechanical bowel obstruction or urinary tract obstruction.
Contraindications
Mestinon must not be used in the following situations:
- Allergy to pyridostigmine bromide or any of the other ingredients in the medication
- Mechanical gastrointestinal obstruction: A physical blockage in the intestinal tract, as the drug's stimulation of bowel motility could worsen the obstruction and potentially lead to perforation
- Urinary tract obstruction: Mechanical blockage of the urinary tract, as increased cholinergic activity could exacerbate urinary retention behind the obstruction
Warnings and Precautions
Your physician should be informed before prescribing Mestinon if you have any of the following conditions, as special caution and potentially adjusted dosing may be required:
- Respiratory conditions: Asthma or chronic obstructive pulmonary disease (COPD), as pyridostigmine can increase bronchial secretions and bronchoconstriction, potentially worsening breathing difficulties
- Cardiac conditions: Heart rhythm disorders (arrhythmias), slow heart rate (bradycardia), low blood pressure (hypotension), or recent coronary occlusion, as cholinergic stimulation can affect cardiac function
- Vagotomy: Disruption of the vagus nerve, which plays a role in the autonomic nervous system and can alter the medication's effects
- Peptic ulcer disease: Active or history of stomach ulcers, as increased cholinergic activity stimulates gastric acid secretion
- Epilepsy or parkinsonism: Conditions affecting the central nervous system that may be exacerbated by cholinergic stimulation
- Thyrotoxicosis (hyperthyroidism): Overactive thyroid gland, which can interact with neuromuscular function
- Renal impairment: Reduced kidney function may affect the clearance of pyridostigmine from the body, potentially requiring dose adjustments
- Thymectomy: Previous surgical removal of the thymus gland, which is relevant to the management strategy for myasthenia gravis
Taking too much Mestinon can cause a cholinergic crisis, which may be difficult to distinguish from a myasthenic crisis (worsening of myasthenia gravis). Both conditions present with severe muscle weakness, but a cholinergic crisis also involves excessive cholinergic symptoms such as profuse sweating, salivation, and small pupils. If you experience worsening symptoms, seek immediate medical attention rather than taking additional doses.
Pregnancy and Breastfeeding
Data from the use of Mestinon in pregnant women is limited. Animal studies have demonstrated effects on fetal development. Therefore, Mestinon should only be used during pregnancy when it is considered absolutely necessary by your physician, and the potential benefits clearly outweigh the risks to the fetus. Women with myasthenia gravis require careful management during pregnancy, as the disease itself can fluctuate during gestation.
Pyridostigmine does pass into breast milk. The decision to breastfeed while taking Mestinon requires careful consideration of both the mother's need for treatment and the potential risks to the nursing infant. Clinical studies have not demonstrated significant adverse effects in breastfed infants when mothers were taking standard doses, but individual circumstances should be discussed with your healthcare provider.
Fertility studies have not shown any negative effects of pyridostigmine on the ability to conceive. However, patients planning pregnancy should discuss their complete treatment plan with their neurologist and obstetrician to optimize outcomes for both mother and child.
Driving and Operating Machinery
During treatment with Mestinon, side effects such as low blood pressure (hypotension) and visual disturbances may occur. These effects should be taken into account when activities requiring heightened alertness are necessary, such as driving motor vehicles or operating heavy machinery. If you experience these symptoms, you should avoid driving until the effects have resolved. Your physician can advise you on whether it is safe to drive while taking this medication.
How Does Mestinon Interact with Other Drugs?
Mestinon can interact with several medications, including immunosuppressants, certain antibiotics, muscle relaxants, anesthetics, and antiarrhythmic drugs. Always inform your physician about all medications you are taking, including over-the-counter medicines and supplements.
Drug interactions with Mestinon can either reduce its therapeutic effect or increase the risk of adverse effects. Understanding these interactions is essential for safe and effective treatment. The following table summarizes the most clinically significant interactions, but this list is not exhaustive. Always consult your physician or pharmacist before starting any new medication while taking Mestinon.
Major Interactions
| Drug / Drug Class | Type of Interaction | Clinical Effect |
|---|---|---|
| Aminoglycoside antibiotics (gentamicin, tobramycin, amikacin) | Antagonistic | Can impair neuromuscular transmission and reduce Mestinon's effectiveness, potentially worsening myasthenia gravis symptoms |
| Neuromuscular blocking agents (suxamethonium, atracurium, vecuronium) | Complex interaction | Mestinon can prolong the effect of depolarizing agents (suxamethonium) and antagonize non-depolarizing agents; requires careful anesthetic management |
| Immunosuppressive agents (corticosteroids, azathioprine, mycophenolate) | May alter response | Initial corticosteroid therapy may temporarily worsen myasthenia; dose adjustments of Mestinon may be needed during initiation of immunosuppressants |
| Antiarrhythmic drugs (beta-blockers, calcium channel blockers, procainamide) | Additive/Antagonistic | Can affect cardiac conduction and potentially worsen bradycardia or cause heart rhythm disturbances when combined with Mestinon's cholinergic effects |
| Atropine and hyoscine (anticholinergic agents) | Antagonistic | Directly oppose the cholinergic effects of Mestinon; sometimes used therapeutically to manage excessive muscarinic side effects, but may reduce therapeutic efficacy |
| Local and general anesthetics | Complex interaction | Anesthetic management in myasthenia gravis patients requires special consideration; inform your anesthetist about Mestinon use before any surgical procedure |
Additional Considerations
Medications containing methylcellulose may affect the absorption of Mestinon from the gastrointestinal tract, potentially reducing its effectiveness. Antispasmodic medications that relax smooth muscle may also counteract some of the gastrointestinal effects of pyridostigmine. Patients should avoid taking any new medications, including herbal supplements and over-the-counter products, without first consulting their healthcare provider.
It is particularly important to inform your anesthesiologist about Mestinon use before any surgical procedure, as the interaction between pyridostigmine and neuromuscular blocking agents used during general anesthesia requires careful management. The European Society of Anaesthesiology and Intensive Care (ESAIC) recommends specific protocols for managing patients with myasthenia gravis during surgical procedures.
What Is the Correct Dosage of Mestinon?
The dosage of Mestinon is individually determined by your physician. For myasthenia gravis, the typical adult dose is 60–180 mg taken 3–6 times daily. For intestinal atony, the usual dose is 60 mg at appropriate intervals, such as every 4 hours. Always take Mestinon with plenty of water.
Mestinon dosing is highly individualized because the severity of myasthenia gravis varies considerably between patients and can fluctuate over time. Your physician will determine the optimal dose based on your specific symptoms, muscle strength assessments, and response to treatment. It is essential that you never adjust your dose without consulting your physician, as both underdosing and overdosing can have serious consequences.
Adults
Myasthenia Gravis
Dose: 60–180 mg per dose
Frequency: 3–6 times daily
Total daily dose: Typically 180–1080 mg, individualized to patient response
The dose is titrated according to the patient's clinical response, aiming to achieve optimal muscle strength without excessive cholinergic side effects. Many patients find that spacing doses evenly throughout waking hours provides the most consistent symptom control. The onset of action is typically 30–45 minutes, and the effect duration is 3–6 hours per dose.
Intestinal Atony
Dose: 60 mg per dose
Frequency: At appropriate intervals, e.g., every 4 hours
For intestinal atony, a lower total daily dose is typically sufficient. The dosing schedule is adjusted based on the patient's bowel response and overall condition.
Children
The use of Mestinon in children with juvenile myasthenia gravis follows similar principles to adult dosing but with weight-based calculations. Pediatric dosing is determined by the treating neurologist and typically starts at a lower dose with careful upward titration based on clinical response. The American Academy of Neurology (AAN) recommends individualized dosing in pediatric patients with careful monitoring of both therapeutic response and side effects.
Elderly Patients
Elderly patients may be more sensitive to the effects of Mestinon, particularly cardiac and gastrointestinal effects. Dose initiation should be cautious, starting at the lower end of the dosing range with gradual titration. Renal function should be assessed before and during treatment, as age-related decline in kidney function may affect drug clearance and necessitate dose adjustments.
Missed Dose
If you miss a dose of Mestinon, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to compensate for a missed dose, as this increases the risk of cholinergic side effects and potentially a cholinergic crisis.
Overdose
An overdose of Mestinon constitutes a medical emergency. If you suspect an overdose, contact your physician, hospital emergency department, or poison control center immediately. Overdose symptoms reflect excessive cholinergic stimulation and may include:
- Respiratory system: Respiratory failure, increased bronchial secretions, bronchospasm
- Gastrointestinal: Severe abdominal cramps, diarrhea, nausea, vomiting, increased salivation
- Musculoskeletal: Muscle cramps, muscle weakness, fasciculations (twitching), generalized weakness, paralysis
- Cardiovascular: Hypotension (low blood pressure), bradycardia (slow heart rate), cardiac arrest
- Neurological: Agitation, confusion, speech disturbances, nervousness, visual hallucinations, seizures, coma
- Other: Pupil constriction (miosis), excessive sweating
If you or someone else has taken too much Mestinon and experiences difficulty breathing, severe muscle weakness, or cardiovascular symptoms, call emergency services immediately. Do not wait for symptoms to worsen. Treatment of cholinergic crisis typically requires atropine and supportive care in a medical facility.
What Are the Side Effects of Mestinon?
Like all medications, Mestinon can cause side effects, although not everyone experiences them. The most common side effects are related to its cholinergic mechanism of action and include gastrointestinal symptoms (nausea, diarrhea, abdominal cramps), increased secretions (saliva, sweat, tears), and muscular effects (twitching, weakness).
The side effects of Mestinon are largely predictable from its pharmacological action as an acetylcholinesterase inhibitor. By increasing acetylcholine levels, the drug enhances both the desired effects at the neuromuscular junction and unwanted cholinergic effects throughout the body. Many side effects are dose-dependent and can often be managed through careful dose adjustment. If any side effects become troublesome, contact your physician – do not adjust your dose on your own.
Common Side Effects
May affect up to 1 in 10 users
- Pupil constriction (miosis) and difficulty focusing, especially on close objects
- Increased tear production and eye inflammation
- Heart rhythm disturbances
- Increased mucus production in the airways (particularly in patients with pre-existing lung disease)
- Breathing difficulties and runny nose
- Nausea, vomiting, and diarrhea
- Increased intestinal motility and abdominal cramps
- Increased saliva and sweat production
- Muscle weakness, muscle twitching, and muscle cramps
- Urinary urgency and loss of appetite
Uncommon Side Effects
May affect up to 1 in 100 users
- Dizziness
- Restlessness
- Difficulty falling asleep (insomnia)
Rare Side Effects
May affect up to 1 in 1,000 users
- Skin rash
- Hair loss (alopecia) with long-term treatment
Very Rare Side Effects
May affect up to 1 in 10,000 users
- Heart rhythm disturbances (arrhythmia)
- Urticaria (hives)
Frequency Not Known
Reported in post-marketing surveillance
- Prinzmetal's angina (variant angina with coronary artery spasm)
- Skin flushing
- Hypotension (low blood pressure)
- Syncope (fainting)
- Drug hypersensitivity reactions
Many of the common side effects of Mestinon are muscarinic cholinergic effects that occur because acetylcholine acts on receptors throughout the body, not just at the neuromuscular junction. Your physician may prescribe a low dose of an anticholinergic medication (such as glycopyrrolate or propantheline) to be taken alongside Mestinon to reduce these unwanted effects while preserving the beneficial neuromuscular effects. Do not take anticholinergic medications without medical advice, as they can mask signs of overdosage.
It is important to report any suspected side effects to your healthcare provider. Post-marketing surveillance relies on voluntary reporting to continuously monitor the benefit-risk balance of medications. Your report contributes to the safe use of medicines for everyone.
How Should You Store Mestinon?
Store Mestinon at or below 25°C (77°F) in a dry place, out of sight and reach of children. Do not use the medication after the expiry date printed on the packaging.
Proper storage of Mestinon is essential to maintain the medication's potency and safety. The sugar-coated 60 mg tablets should be stored at a temperature not exceeding 25°C (77°F). Keep the medication in its original packaging to protect it from moisture and light. Do not store Mestinon in the bathroom or other humid environments, as moisture can degrade the medication.
Always check the expiry date before taking a dose. The expiry date refers to the last day of the month indicated on the packaging. Do not use Mestinon after this date. Unused or expired medication should not be disposed of via household waste or flushed down the drain. Return unused medication to your pharmacy for proper disposal, which helps protect the environment.
Keep Mestinon and all medications out of the sight and reach of children. The sugar coating may make the tablets appear attractive to young children, making proper storage particularly important. Consider using a child-resistant storage location or container if children are present in the household.
What Does Mestinon Contain?
The active ingredient in Mestinon is pyridostigmine bromide. The 60 mg sugar-coated tablets contain sucrose (162 mg) and various excipients including rice starch, talc, acacia, paraffin, colloidal silicon dioxide, maize starch, povidone, magnesium stearate, and iron oxide colorants (E172).
Understanding the composition of your medication is important, particularly if you have known allergies or intolerances to certain substances. The complete ingredient list for Mestinon 60 mg sugar-coated tablets is as follows:
Active substance: Pyridostigmine bromide 60 mg
Inactive ingredients (excipients):
- Sucrose: 162 mg per tablet (used in the sugar coating) – patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase insufficiency should not take this medicine
- Rice starch: Used as a filler and binding agent
- Talc: Used as a glidant to improve tablet manufacturing
- Acacia (gum arabic): Used in the sugar coating as a binding agent
- Solid paraffin and liquid paraffin: Used in the coating for surface polish
- Colloidal anhydrous silicon dioxide: Used as a flow agent
- Maize starch: Used as a disintegrant to facilitate tablet dissolution
- Povidone: Used as a binding agent
- Pregelatinized potato starch: Used as a binder and disintegrant
- Magnesium stearate: Used as a lubricant during tablet pressing
- Red and yellow iron oxide (E172): Colorants in the sugar coating, giving the tablet its characteristic beige appearance
Appearance: Mestinon 60 mg tablets are beige, biconvex sugar-coated tablets supplied in glass bottles containing 150 tablets.
If you have been told by your physician that you have an intolerance to some sugars, contact your physician before taking Mestinon, as the 60 mg sugar-coated tablets contain sucrose (162 mg per tablet). This is particularly relevant for patients with diabetes who need to account for all sources of sugar in their diet.
Frequently Asked Questions About Mestinon
Mestinon (pyridostigmine bromide) is primarily used to treat myasthenia gravis, a chronic autoimmune condition that causes severe muscle weakness and fatigue. It works by preventing the breakdown of the neurotransmitter acetylcholine, which helps improve communication between nerves and muscles. Mestinon is also used to treat intestinal atony (reduced bowel motility), where it stimulates smooth muscle contractions in the gastrointestinal tract. It does not cure myasthenia gravis but provides symptomatic relief and is often used alongside immunosuppressive therapies.
Mestinon typically begins to take effect within 30 to 45 minutes after oral administration. The peak effect occurs at approximately 1 to 2 hours, and each dose provides relief for approximately 3 to 6 hours, depending on the dose size and individual patient factors. Because of its relatively short duration of action, most patients with myasthenia gravis need to take Mestinon multiple times throughout the day (typically 3 to 6 times) to maintain consistent symptom control.
Yes, Mestinon can be taken with or without food. However, taking it with food may help reduce some of the gastrointestinal side effects such as nausea, abdominal cramps, and diarrhea that can occur with this medication. It is important to take Mestinon with plenty of water regardless of whether you take it with food. Some patients find that taking the medication shortly before meals helps optimize muscle strength for chewing and swallowing, which can be particularly beneficial for those with oropharyngeal muscle weakness.
A myasthenic crisis occurs when myasthenia gravis symptoms worsen to the point where respiratory muscles are significantly affected, typically due to insufficient treatment. A cholinergic crisis, on the other hand, results from too much acetylcholinesterase inhibitor medication (overdose of Mestinon). Both conditions present with severe muscle weakness and respiratory difficulty, making them difficult to distinguish. However, a cholinergic crisis also produces excessive muscarinic symptoms including profuse sweating, salivation, small pupils (miosis), abdominal cramps, and diarrhea. Both are medical emergencies requiring immediate hospital care. Never attempt to self-diagnose or self-treat either condition.
While there is no specific absolute contraindication to alcohol consumption with Mestinon, alcohol can worsen muscle weakness and fatigue, which are the very symptoms Mestinon is meant to treat. Alcohol can also increase the risk of side effects such as dizziness, drowsiness, and gastrointestinal disturbances. Furthermore, alcohol may affect the absorption and metabolism of medications. It is advisable to discuss alcohol consumption with your physician, who can provide personalized advice based on your specific medical situation and symptom severity.
If you notice that Mestinon is becoming less effective, do not increase the dose on your own. Reduced effectiveness may indicate disease progression, the need for immunosuppressive therapy, or may sometimes suggest overmedication (where excess acetylcholine actually causes additional weakness). Contact your neurologist to reassess your treatment. They may adjust your Mestinon dose, add or modify immunosuppressive medications, or investigate other factors that may be affecting your muscle strength, such as infections, medication interactions, or metabolic imbalances.
References
This article is based on the following international medical guidelines, regulatory documents, and peer-reviewed research. All medical information has been reviewed according to evidence level 1A standards (systematic reviews and meta-analyses of randomized controlled trials).
- Sanders DB, Wolfe GI, Benatar M, et al. "International consensus guidance for management of myasthenia gravis." Neurology. 2016;87(4):419-425. American Academy of Neurology (AAN).
- Sussman J, Farrugia ME, Maddison P, et al. "Myasthenia gravis: Association of British Neurologists' management guidelines." Practical Neurology. 2015;15(3):199-206.
- Gilhus NE, Tzartos S, Evoli A, et al. "Myasthenia gravis." Nature Reviews Disease Primers. 2019;5(1):30.
- European Federation of Neurological Societies/European Neurological Society (EFNS/ENS). "Guidelines for the treatment of autoimmune neuromuscular transmission disorders." European Journal of Neurology. 2023.
- World Health Organization (WHO). WHO Model List of Essential Medicines. 23rd List. Geneva: WHO; 2023.
- British National Formulary (BNF). "Pyridostigmine bromide." National Institute for Health and Care Excellence (NICE). 2024.
- European Medicines Agency (EMA). Summary of Product Characteristics: Pyridostigmine bromide. 2024.
- U.S. Food and Drug Administration (FDA). Prescribing Information: Mestinon (pyridostigmine bromide) Tablets. Valeant Pharmaceuticals.
- Maggi L, Mantegazza R. "Treatment of myasthenia gravis: focus on pyridostigmine." Clinical Drug Investigation. 2011;31(10):691-701.
- Farmakidis C, Pasnoor M, Dimachkie MM, Barohn RJ. "Treatment of Myasthenia Gravis." Neurologic Clinics. 2018;36(2):311-337.
About the Medical Editorial Team
This article has been written and medically reviewed by the iMedic Medical Editorial Team, comprising licensed specialist physicians with expertise in neurology, clinical pharmacology, and internal medicine.
Medical Review Board
Independent panel of board-certified physicians who verify accuracy, completeness, and adherence to current clinical guidelines (AAN, EFNS/ENS, NICE, WHO).
Evidence Standards
All content follows the GRADE evidence framework. Drug information is cross-referenced with EMA, FDA, BNF, and WHO sources. No commercial funding or pharmaceutical sponsorship.