Neostig

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.

Anti-arrhythmic Procainamide, Quinidine and possibly Propafenone antagonise effect of Neostigmine. Antibacterials, Aminoglycosides, Clindamycin, Lincomycin and Polymyxins antagonise effect of Neostigmine.

Nausea, vomiting, increased salivation, diarrhoea and abdominal cramps (more marked with high doses). Signs of overdose are increased gastrointestinal discomfort, bronchial secretions and sweating, involuntary defecation and micturition, miosis, nystagmus, bradycardia, hypotension, agitation, excessive dreaming and weakness eventually leading to fasciculation and paralysis.

Pregnancy Category C. There are no adequate or well-controlled studies of Neostigmine in either laboratory animals or in pregnantwomen. It is not known whether Neostigmine can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Neostigmine should be given to a pregnant woman only if clearly needed.

Nonteratogenic Effects: Anticholinesterase drugs may cause uterine irritability and induce premature labor when given intravenously to pregnant women near term.

Nursing Mothers: It is not known whether Neostigmine is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions from Neostigmine in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Asthma, bradycardia, recent myocardial infarction, epilepsy, hypotension, parkinsonism, vagotonia, peptic ulceration. Atropine or other antidote to muscarinic effccts may be necessary (particularly when Neostigmine is given by injection), but it should not be given routinely as it may mask signs of overdose.

Anti-cholinesterases, Drugs used in Myasthenia Gravis

Store in a cool and dry place, protected from light.