Neostigmine is a parasympathomimetic, specifically, a reversible cholinesterase inhibitor. By interfering with the breakdown of acetylcholine, Neostigmine indirectly stimulates both nicotinic and muscarinic receptors. It does cross the blood-brain barrier but only poorly. Neostigmine binds to the anionic site of cholinesterase. The drug blocks the active site of acetylcholinesterase; so the enzyme can no longer break down the acetylcholine molecules before they reach the postsynaptic membrane receptors. This allows for the threshold to be reached so a new impulse can be triggered in the next neuron. In myasthenia gravis there are too few acetylcholine receptors. So with the acetylcholinesterase blocked, acetylcholine can bind to the few receptors and trigger a muscular contraction.
Reversal of the effects of Non-depolarizing Neurormuscular Blocking Agents: The usual dose is 0.5 to 2 mg given by slow intravenous injection over 60 seconds; repeated as required. Total dose should not exceed 5 mg (in exceptional cases). When Neostigmine is administered intravenously, it is recommended that Atropine Sulphate (0.6-1.2 mg) also be given intravenously using separate syringe.
Prevention of post-operative abdominal distention and urinary retention: 0.25 mg intramuscularly or subcutaneously as soon as possible after operation; repeat every 4 6 hours for 2-3 days.
Treatment of post-operative abdominal distention: 0.5 mg intramuscularly or subcutaneously or as required.
Treatment of urinary retention: 0.5 mg intramuscularly or subcutaneously. If urination does not occur within an hour, the patient should be catheterized. After the patient has voided, or the bladder has been emptied, continue the 0.5 mg injection every 3 hours, for at least 5 injections.
Symptomatic control of Myasthenia Gravis: 0.5 mg intramuscularly or subcutaneously. Subsequent dose should be based on the individual patient’s response.
Neonates: 50-250 micrograms (0.1 to 0.5 ml) every 4 hours.
Children: 200-500 micrograms (0.4 ml to 1 ml) as recommended.