Mestinon (Pyridostigmine)

Mestinon acts on the cholinergic neuromuscular system and is indicated for several recognized conditions.

• Myasthenia gravis: improves skeletal muscle strength and reduces fatigue.
• Ocular myasthenia: enhances eye muscle function and alleviates double vision.
• Reversal of non‑depolarizing neuromuscular blockade: restores normal neuromuscular transmission after anesthesia.

• 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, thereby improving muscle contraction and counteracting the effects of neuromuscular blocking agents.

Pyridostigmine may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Diarrhea: increased bowel movements.
• Abdominal cramps: discomfort in the stomach area.
• Increased salivation: excess oral secretions.
• Muscle cramps: involuntary tightening of muscles.
• Sweating: heightened perspiration.

Serious or Rare Side Effects

• Cholinergic crisis: severe muscle weakness requiring emergency care.
• Bradycardia: markedly slow heart rate.
• Bronchospasm: narrowing of airways causing breathing difficulty.
• Allergic reaction: rash, itching, or swelling.
• Seizures: rare neurologic events.
• Severe hypotension: dangerous drop in blood pressure.

When prescribing or dispensing Mestinon, consider the following safety measures.

• Renal impairment: adjust dose because the drug is renally excreted.
• Cholinergic crisis: monitor for signs of excessive cholinergic activity.
• Asthma or COPD: use caution as increased secretions may exacerbate airway obstruction.
• Concomitant anticholinergics: avoid because they may diminish therapeutic effect.
• Pregnancy and lactation: safety data are limited; weigh benefits against potential risks.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Pyridostigmine can interact with several medicines, requiring attention to avoid reduced efficacy or toxicity.

Major Interactions (Avoid)

• Anticholinergic agents (e.g., atropine, scopolamine): may counteract pyridostigmine's action.
• Other cholinesterase inhibitors (e.g., neostigmine): increase risk of cholinergic excess.

Moderate Interactions (Monitor Closely)

• Beta‑blockers: may potentiate bradycardia.
• Magnesium sulfate: can enhance neuromuscular blockade.
• Diuretics (e.g., furosemide): may affect renal clearance of pyridostigmine.
• Inhaled bronchodilators: monitor for altered respiratory response.