Neostigmine

Can cause excess Acetyl Choline and Parasympathetic actions with a Cholinergic crisis/syndrome with salivation and bronchial secretion, severe bronchospasm, cardiac arrhythmias, asystole, hypotension, muscle cramps and seizures. All these are the outcome of excessive parasympathetic activity. Therefore, the patient should always be monitored and any toxicity should be reversed by atropine.

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Mode of action

• Therapeutic effect lasts for up to 4 hours
• Inhibit action of acetylcholinesterase which prolongs the action of Ach
• In excess can impair action and worsen weakness
• It can precipitate cholinergic crises by causing a depolarising block.
• This may be difficult to distinguish from a worsening myasthenic state.

Indications/Dose

• Myasthenia Gravis, Reverse actions of the non-depolarising neuromuscular blocking drugs: Max dose Neostigmine 180 mg daily PO. Neostigmine bromide 15-30 mg PO throughout day up to 180 mg/day
• Myasthenia Gravis, Colonic Pseudo obstruction: Neostigmine 2mg by IM/IV/SC injection at intervals throughout the day, when maximum strength is needed. The usual duration of action of a dose is two to four hours. The total daily dose is usually 5-20mg by injection but higher doses may be needed by some patients.

Interactions

• See BNF

Cautions

• Asthma, bradycardia, arrhythmias, recent MI
• Epilepsy, hypotension, parkinsonism, peptic ulceration, hyperthyroidism

Contraindications

• Bowel/Urinary obstruction

Side effects

• Acetyl choline on muscarinic sites: sweating, colic, excessive salivation, or diarrhoea, excess gastric secretions, bradycardia.
• Monitor patient. Be prepared to reverse with Atropine like drugs.

References