Trade name Tensilon.

Refers to a readily reversible acetylcholinesterase inhibitor, that prevents breakdown of the neurotransmitter acetylcholine and acts by competitively inhibiting the enzyme acetylcholinesterase, mainly at the neuromuscular junction.

It is used to differentiate myasthenia gravis from cholinergic crisis and Eaton-Lambert syndrome.

In myasthenia gravis, the body produces autoantibodies which block, inhibit or destroy nicotinic acetylcholine receptors in the neuromuscular junction.

Edrophonium being an effective acetylcholinesterase inhibitor reduces the muscle weakness by blocking the enzymatic effect of acetylcholinesterase enzymes, prolonging the presence of acetylcholine in the synaptic cleft.

Edrophonium binds to a Serine-103 allosteric site, while pyridostigmine and neostigmine bind to the AchE active site for their inhibitory effects.

In a cholinergic crisis, where a person has too much neuromuscular stimulation, edrophonium will make the muscle weakness worse by inducing a depolarizing block.

The Eaton- Lambert myasthenic syndrome is similar to myasthenia gravis in that it is an autoimmune disease.

However, in the Eaton- Lambert myasthenic syndrome the neuron is unable to release enough acetylcholine for normal muscle function due to autoantibodies attacking P/Q-type calcium channel, necessary for acetylcholine release.

This means there is insufficient calcium ion influx into presynaptic terminal resulting in reduced exocytosis of acetylcholine containing vesicles, so there will typically be not as much increase in muscle strength observed after edrophonium injection, if any the Eaton- Lambert myasthenic syndrome.

The test may also be used to predict if neurotoxic paralysis caused by snake envenomation is presynaptic or postsynaptic.

The drug may also be used for postoperative decurarization.

The drug has a duration of action of about 10–30 mins.

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