Neostigmine: Uses, Mechanism & Dosage
Neostigmine is a cholinesterase inhibitor used in the treatment of myasthenia gravis, reversal of neuromuscular blockade, and intestinal atony.
Things worth knowing about "Neostigmine"
Neostigmine is a cholinesterase inhibitor used in the treatment of myasthenia gravis, reversal of neuromuscular blockade, and intestinal atony.
What is Neostigmine?
Neostigmine is a reversible acetylcholinesterase inhibitor that has been used in clinical medicine for decades. It belongs to the class of parasympathomimetic agents and enhances the effect of the endogenous neurotransmitter acetylcholine by blocking its breakdown by the enzyme acetylcholinesterase. As a synthetic quaternary ammonium compound, neostigmine does not readily cross the blood-brain barrier, so its effects are predominantly peripheral rather than central.
Mechanism of Action
Neostigmine reversibly inhibits the enzyme acetylcholinesterase, which normally degrades acetylcholine at the neuromuscular junction and at parasympathetic synapses. By blocking this enzyme, acetylcholine accumulates in the synaptic cleft and stimulates both nicotinic receptors (at skeletal muscle) and muscarinic receptors (at smooth muscle, the heart, and glands). This results in enhanced and prolonged cholinergic activity throughout the body.
Indications (Medical Uses)
- Myasthenia gravis: Neostigmine improves neuromuscular transmission in this autoimmune disease, where antibodies block or destroy acetylcholine receptors at the neuromuscular junction.
- Reversal of non-depolarizing neuromuscular blockade: After surgery performed under general anaesthesia, neostigmine is used to reverse the effects of muscle relaxants such as rocuronium or vecuronium and to restore spontaneous breathing.
- Postoperative ileus and intestinal atony: Neostigmine stimulates intestinal motility and can be used in cases of functional bowel obstruction (Ogilvie syndrome, paralytic ileus).
- Urinary retention: In selected cases, neostigmine may be used to treat functional urinary retention by promoting bladder contraction.
Dosage and Administration
Neostigmine is administered by different routes depending on the indication:
- Injection (intramuscular, subcutaneous, or intravenous): Commonly used in anaesthesia for neuromuscular reversal, typically 0.03–0.07 mg/kg body weight intravenously, usually combined with an anticholinergic agent (e.g., atropine) to suppress unwanted muscarinic side effects.
- Oral tablets: Used in myasthenia gravis with individually adjusted dosing; a typical adult dose is 15–30 mg every 3–4 hours.
The exact dose is always determined individually based on the indication, body weight, and clinical condition of the patient.
Side Effects
Because neostigmine enhances acetylcholine activity at all cholinergic synapses, the following cholinergic side effects may occur:
- Increased salivation, sweating, and lacrimation
- Nausea, vomiting, diarrhea, and abdominal cramps
- Bradycardia (slowed heart rate)
- Bronchospasm and increased bronchial secretions
- Miosis (pupil constriction)
- Muscle fasciculations (involuntary muscle twitching) in cases of overdose
To prevent these side effects, neostigmine is frequently co-administered with atropine in anaesthetic practice, which blocks the muscarinic effects while preserving the desired nicotinic reversal at the neuromuscular junction.
Contraindications
- Mechanical intestinal or urinary tract obstruction
- Hypersensitivity to neostigmine or any excipients of the preparation
- Severe bradycardia or atrioventricular block
- Peritonitis
- Bronchial asthma (relative contraindication)
Special Warnings
Neostigmine should only be used under medical supervision and in appropriately equipped facilities. Overdose may lead to a cholinergic crisis, characterized by profound muscle weakness, excessive secretions, bradycardia, and respiratory failure. The antidote is atropine, which counteracts the muscarinic effects of excessive cholinergic stimulation.
References
- Rang H.P., Dale M.M., Ritter J.M., Flower R.J., Henderson G.: Rang and Dale's Pharmacology, 9th edition, Elsevier, 2019.
- Brunton L.L., Hilal-Dandan R., Knollmann B.C. (eds.): Goodman & Gilman's The Pharmacological Basis of Therapeutics, 13th edition, McGraw-Hill, 2018.
- European Medicines Agency (EMA): Neostigmine - Product Information and Assessment Reports. Available at: https://www.ema.europa.eu (accessed 2024).
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