Makindo Medical Notes

⚠️ Neostigmine increases acetylcholine activity at both nicotinic and muscarinic receptors. Excessive dosing can cause a cholinergic crisis with salivation, bronchospasm, bradyarrhythmias, hypotension, muscle cramps, and seizures. Always monitor patients closely and be ready to reverse severe muscarinic toxicity with atropine.

📖 About

Neostigmine is a reversible acetylcholinesterase inhibitor. Check the BNF link here.

⚡ Mode of Action

• Inhibits acetylcholinesterase → prolongs action of acetylcholine at the neuromuscular junction.
• Duration of effect: ~2–4 hours.
• Improves neuromuscular transmission in Myasthenia Gravis.
• In excess, causes depolarising block → worsens weakness (difficult to distinguish from myasthenic crisis).

💊 Indications & Dose

• Myasthenia Gravis:
  • Oral: 15–30 mg throughout the day, up to 180 mg/day.
  • Parenteral: 2 mg IM/IV/SC, repeated as needed (total daily 5–20 mg, sometimes higher).
• Reversal of non-depolarising neuromuscular blockade: with atropine or glycopyrronium to counter muscarinic effects.
• Colonic pseudo-obstruction: IV neostigmine (2 mg over 3–5 mins, with resus facilities available).

🤝 Interactions

• See BNF for full list. Key: additive bradycardia with β-blockers or digoxin; antagonised by corticosteroids.

⚠️ Cautions

• Asthma or COPD (risk of bronchospasm).
• Bradycardia, conduction disorders, recent MI.
• Epilepsy, Parkinsonism.
• Peptic ulcer disease, hyperthyroidism.

🚫 Contraindications

• Bowel or urinary obstruction (risk of perforation or retention).

💥 Side Effects

• Muscarinic effects: Sweating, salivation, diarrhoea, colic, bronchospasm, bradycardia, hypotension.
• Nicotinic effects: Muscle cramps, fasciculations, weakness (esp. in overdose).
• Other: Headache, seizures (rare).
• ⚠️ Severe toxicity = cholinergic crisis → treat with atropine ± ventilatory support.

🩺 Clinical Pearls

• 💡 Myasthenic vs Cholinergic Crisis: Both present with weakness; a trial dose of edrophonium (historically) or careful specialist assessment helps distinguish.
• Always co-administer atropine or glycopyrronium when reversing neuromuscular blockade to avoid severe bradycardia.
• Monitor ECG and airway closely when giving IV for pseudo-obstruction.

📚 References

• BNF – Neostigmine
• Association of Anaesthetists: Guidelines for the Management of Neuromuscular Blockade