โ ๏ธ 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.
๐ About
Neostigmine is a reversible acetylcholinesterase inhibitor.
Check the BNF link here.
โก Mode of Action
- Inhibits acetylcholinesterase โ prolongs action of acetylcholine at the neuromuscular junction.
- Duration of effect: ~2โ4 hours.
- Improves neuromuscular transmission in Myasthenia Gravis.
- In excess, causes depolarising block โ worsens weakness (difficult to distinguish from myasthenic crisis).
๐ Indications & Dose
- Myasthenia Gravis:
- Oral: 15โ30 mg throughout the day, up to 180 mg/day.
- Parenteral: 2 mg IM/IV/SC, repeated as needed (total daily 5โ20 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 3โ5 mins, with resus facilities available).
๐ค Interactions
- See BNF for full list. Key: additive bradycardia with ฮฒ-blockers or digoxin; antagonised by corticosteroids.
โ ๏ธ Cautions
- Asthma or COPD (risk of bronchospasm).
- Bradycardia, conduction disorders, recent MI.
- Epilepsy, Parkinsonism.
- Peptic ulcer disease, hyperthyroidism.
๐ซ Contraindications
- Bowel or urinary obstruction (risk of perforation or retention).
๐ฅ Side Effects
- Muscarinic effects: Sweating, salivation, diarrhoea, colic, bronchospasm, bradycardia, hypotension.
- Nicotinic effects: Muscle cramps, fasciculations, weakness (esp. in overdose).
- Other: Headache, seizures (rare).
- โ ๏ธ Severe toxicity = cholinergic crisis โ treat with atropine ยฑ ventilatory support.
๐ฉบ Clinical Pearls
- ๐ก 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.
๐ References
- BNF โ Neostigmine
- Association of Anaesthetists: Guidelines for the Management of Neuromuscular Blockade
