Mestinon (pyridostigmine bromide) is a first-line acetylcholinesterase inhibitor medication specifically formulated for the symptomatic treatment of myasthenia gravis. It works by improving communication between nerves and muscles, leading to a significant enhancement in muscular strength and endurance. This agent is a cornerstone of therapy, providing patients with increased functional capacity and a better quality of life. Its well-established efficacy and safety profile have made it a trusted choice for neurologists and patients for decades.

Features

• Active ingredient: Pyridostigmine Bromide
• Available in 60 mg scored tablets and 180 mg extended-release tablets
• Also available as a 5 mg/mL oral syrup formulation
• Cholinesterase inhibitor pharmacologic class
• Onset of action: Approximately 30-45 minutes for standard tablets
• Duration of effect: 3-4 hours for standard tablets, 6-8 hours for extended-release formulation

Benefits

• Rapid Improvement in Muscle Strength: Effectively reduces the hallmark muscle weakness and fatigue associated with myasthenia gravis, allowing for improved mobility and daily function.
• Enhanced Quality of Life: By mitigating symptoms like ptosis (drooping eyelids), diplopia (double vision), and difficulties with chewing, swallowing, and speech, patients can engage more fully in social and occupational activities.
• Flexible Dosing Options: The availability of standard tablets, extended-release tablets, and oral syrup allows for tailored treatment regimens to match individual patient needs and symptom patterns throughout the day.
• Well-Established Safety Profile: Decades of clinical use have provided a deep understanding of its effects, side effects, and management, making it a predictable and reliable therapeutic agent.
• Diagnostic Utility: The Tensilon test, using edrophonium (a related short-acting agent), or observation of response to Mestinon, can be used to support a diagnosis of myasthenia gravis.
• Adjunct to Other Therapies: Works effectively alongside immunosuppressive therapies, thymectomy, and plasma exchange, often serving as the initial symptomatic control while longer-term strategies take effect.

Common use

Mestinon is primarily indicated for the treatment of myasthenia gravis, an autoimmune disorder characterized by weakness and rapid fatigue of voluntarily controlled muscles. It is used for both diagnostic purposes and for chronic symptomatic management. It may also be used in other medical situations, such as the reversal of non-depolarizing neuromuscular blocking agents after surgery (via intravenous administration of a different salt, pyridostigmine methylsulfate) and, less commonly, for the management of orthostatic hypotension. Its use is almost always directed by a neurologist or another specialist familiar with neuromuscular disorders.

Dosage and direction

Dosage is highly individualized based on the patient’s symptoms, response, and tolerance. Treatment is typically initiated at a low dose and carefully titrated upward.

• For standard tablets (60 mg): The typical starting dose for adults is 30-60 mg administered orally every 4-6 hours while awake. The dosage may be gradually increased based on patient response, with a usual maintenance dose ranging from 600 mg to 1500 mg per day, divided into 5 or 6 doses. Dosing intervals are critical and are often scheduled before meals to assist with mastication and swallowing.
• For extended-release tablets (180 mg): These are typically used for overnight coverage to prevent morning weakness. One 180 mg tablet is taken at bedtime. It is crucial that patients do not crush or chew these tablets, as this can lead to a sudden, dangerous release of the entire dose.
• Dosing must be meticulously timed to provide coverage during periods of greatest need (e.g., before meals, before physical activity) and to avoid cholinergic crisis from overdosage.

The timing of doses in relation to meals may be adjusted if abdominal cramping or diarrhea occurs. A healthcare provider must always determine the precise dosage and schedule.

Precautions

Patients taking Mestinon should be closely monitored by their physician. Caution is advised for patients with a history of:

• Asthma or chronic obstructive pulmonary disease (COPD): Bronchoconstriction and increased bronchial secretions can occur.
• Bradycardia (slow heart rate) or arrhythmias: Mestinon can further slow the heart rate.
• Peptic ulcer disease: May increase gastric acid secretion.
• Hyperthyroidism: May exaggerate the side effects of the medication.
• Renal impairment: Dosage adjustment may be necessary as the drug is excreted by the kidneys.
• Pregnancy and Lactation: Should be used during pregnancy only if clearly needed. It may cause uterine irritability. It is excreted in breast milk; caution is advised.

Patients should be educated to recognize the signs of both myasthenic crisis (under-treatment) and cholinergic crisis (over-treatment), as the muscle weakness can appear similar.

Contraindications

Mestinon is contraindicated in patients with:

• Known hypersensitivity or allergy to pyridostigmine bromide or any component of the formulation.
• Mechanical intestinal or urinary obstruction. The drug increases smooth muscle tone and can exacerbate these conditions.
• Peritonitis or acute inflammatory bowel disease.

Possible side effect

Side effects are generally related to the increased cholinergic activity and are often dose-dependent. Common side effects include:

• Gastrointestinal: Nausea, vomiting, diarrhea, abdominal cramping, increased salivation, and increased gastrointestinal motility.
• Muscarinic effects: Increased sweating, increased bronchial and salivary secretions, lacrimation (tearing), miosis (pupil constriction).
• Nicotinic effects: Muscle cramps, fasciculations (muscle twitching), and weakness (if excessive, can indicate cholinergic crisis).

More serious side effects requiring immediate medical attention include: severe dizziness, slow or irregular heartbeat, severe stomach pain, shortness of breath, and significant weakness.

Drug interaction

Mestinon can interact with several other classes of medication:

• Other Cholinesterase Inhibitors: Concurrent use with drugs like neostigmine, ambenonium, or rivastigmine can lead to additive effects and toxicity.
• Anticholinergic Agents: Drugs like atropine, glycopyrrolate, benztropine, and certain antidepressants can antagonize the muscarinic effects of Mestinon (e.g., reducing abdominal cramps) but may mask the early signs of a cholinergic overdose.
• Beta-Blockers: May have additive effects on heart rate, potentiating bradycardia.
• Succinylcholine: Mestinon can potentiate the neuromuscular blocking effects of this depolarizing agent.
• Non-depolarizing Neuromuscular Blocking Agents: Mestinon is used to reverse the effects of these drugs (e.g., rocuronium, vecuronium) after surgery.
• Corticosteroids: Initiation of high-dose corticosteroids for myasthenia gravis can paradoxically cause a temporary worsening of weakness, potentially necessitating a temporary adjustment of the Mestinon dose.

A complete list of all medications, including over-the-counter drugs and supplements, must be reviewed with a doctor or pharmacist.

Missed dose

If a dose is missed, it should be taken as soon as it is remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped. Patients should never double a dose to make up for a missed one, as this significantly increases the risk of a cholinergic crisis. It is essential to maintain the regular dosing schedule.

Overdose

An overdose of Mestinon leads to a cholinergic crisis, characterized by severe muscarinic and nicotinic overstimulation. Symptoms include:

• Severe nausea, vomiting, diarrhea, and abdominal cramps.
• Increased salivation, sweating, and tearing.
• Pupil constriction (miosis).
• Bradycardia, hypotension.
• Increased bronchial secretions, leading to respiratory difficulty and pulmonary edema.
• Muscle fasciculations followed by profound weakness or paralysis, including respiratory muscles.

A cholinergic crisis is a medical emergency requiring immediate hospitalization. Treatment involves withdrawal of Mestinon, respiratory support, and administration of the antidote, atropine sulfate, intravenously.

Storage

• Store at room temperature (20°C to 25°C or 68°F to 77°F).
• Keep the container tightly closed to protect from moisture and light.
• Keep all medications out of the reach of children and pets.
• Do not use after the expiration date printed on the container.
• Do not flush medications down the toilet or pour them down a drain unless instructed to do so. Dispose of unused medication through a medicine take-back program.

Disclaimer

This information is for educational purposes only and is not a substitute for the professional medical advice, diagnosis, or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Never disregard professional medical advice or delay in seeking it because of something you have read here. The information provided may not cover all possible uses, directions, precautions, drug interactions, or adverse effects.

Reviews

• Clinical Consensus: Mestinon is universally regarded by neurologists as the foundational symptomatic therapy for myasthenia gravis. Its rapid onset and predictable effect make it indispensable for daily management. Reviews in medical literature consistently highlight its role in improving functional outcomes and quality of life metrics for patients.
• Patient Perspectives: Many patients report a “life-changing” effect, noting the return of abilities like chewing food, holding their head up, and speaking clearly. The main criticisms from patients often relate to the side effects (particularly gastrointestinal) and the challenge of managing a strict, multi-dose daily schedule. The extended-release formulation is frequently praised for preventing debilitating morning weakness.