Mestinon (Pyridostigmine Bromide)

Mestinon (pyridostigmine) is used in disorders of neuromuscular transmission.

• Myasthenia gravis: improves skeletal muscle strength and reduces fatigue.
• Reversal of non‑depolarizing neuromuscular blockade: restores spontaneous breathing after anesthesia.
• Myasthenic crisis: provides temporary support of respiratory muscles while definitive therapy is initiated.

• Pyridostigmine reversibly inhibits acetylcholinesterase at the neuromuscular junction, preventing the breakdown of acetylcholine. The resulting increase in acetylcholine concentration enhances stimulation of nicotinic receptors on skeletal muscle, improving neuromuscular transmission and muscle contraction. This action is rapid, dose‑dependent, and does not cross the blood‑brain barrier in significant amounts.

Adverse reactions may range from mild to severe and should be monitored during therapy.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Diarrhea: increased bowel movements.
• Abdominal cramps: intermittent stomach discomfort.
• Excessive salivation: drooling or watery mouth.
• Sweating: generalized hyperhidrosis.
• Muscle cramps: involuntary limb tightening.

Serious or Rare Side Effects

• Cholinergic crisis: severe muscle weakness and respiratory failure.
• Bradycardia: markedly slow heart rate requiring medical attention.
• Bronchospasm: narrowing of airways causing breathing difficulty.
• Allergic reactions: rash, itching, or anaphylaxis.
• Seizures: rare central nervous system events.
• Hypotension: sudden drop in blood pressure.

When prescribing Mestinon, clinicians should consider several safety measures.

• Renal impairment: adjust dose because the drug is primarily excreted unchanged.
• Asthma or COPD: monitor for bronchospasm due to cholinergic stimulation.
• Cardiovascular disease: watch for bradycardia or arrhythmias.
• Pregnancy: safety not established; use only if benefit outweighs risk.
• Breastfeeding: unknown excretion in milk; assess risk before use.
• Store at room temperature: keep in original packaging, protect from moisture and direct sunlight.

Pyridostigmine may interact with other medicines, altering its efficacy or safety.

Major Interactions (Avoid)

• Anticholinergic agents (e.g., atropine): opposite pharmacologic effect reduces benefit.
• Aminoglycoside antibiotics: may potentiate neuromuscular blockade.
• Other cholinesterase inhibitors: risk of excessive cholinergic activity.

Moderate Interactions (Monitor Closely)

• Beta‑blockers: additive bradycardic effect.
• Diuretics: potential electrolyte disturbances.
• Anesthetic agents (e.g., volatile anesthetics): may enhance neuromuscular effects.
• Muscle relaxants: may require dose adjustment.
• NSAIDs: monitor for gastrointestinal irritation.