Edrophonium test

Edrophonium

Clinical data
Trade names	Tensilon
AHFS/Drugs.com	FDA Professional Drug Information
ATC code	none
Identifiers
IUPAC name N-Ethyl-3-hydroxy-N,N-dimethylbenzenaminium
CAS Number	312-48-1 N
PubChem CID	8307
DrugBank	DB01010 Y
ChemSpider	8006 Y
UNII	70FP3JLY7N
KEGG	D00994 Y
ChEBI	CHEBI:4759 Y
ChEMBL	CHEMBL1128 Y
ECHA InfoCard	100.003.763
Chemical and physical data
Formula	C10H16NO+
Molar mass	166.24 g/mol
3D model (Jmol)	Interactive image
SMILES [Cl-].Oc1cccc(c1)[N+](C)(CC)C
InChI InChI=1S/C10H15NO.ClH/c1-4-11(2,3)9-6-5-7-10(12)8-9;/h5-8H,4H2,1-3H3;1H Y Key:BXKDSDJJOVIHMX-UHFFFAOYSA-N Y
NY (what is this?)

Edrophonium is a readily reversible acetylcholinesterase inhibitor. It prevents breakdown of the neurotransmitter acetylcholine and acts by competitively inhibiting the enzyme acetylcholinesterase, mainly at the neuromuscular junction. It is sold under the trade names Tensilon and Enlon (according to FDA Orange Book).

Edrophonium (by the so-called Tensilon test) is used to differentiate myasthenia gravis from cholinergic crisis and Lambert-Eaton myasthenic syndrome. In myasthenia gravis, the body produces autoantibodies which block, inhibit or destroy nicotinic acetylcholine receptors in the neuromuscular junction. Edrophonium—an effective acetylcholinesterase inhibitor—will reduce the muscle weakness by blocking the enzymatic effect of acetylcholinesterase enzymes, prolonging the presence of acetylcholine in the synaptic cleft. It 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.

Lambert-Eaton myasthenic syndrome (LEMS), is similar to myasthenia gravis in that it is an autoimmune disease. However, in LEMS the neuron is unable to release enough acetylcholine for normal muscle function due to autoantibodies attacking P/Q-type calcium channel that are necessary for acetylcholine release. This means there is insufficient calcium ion influx into presynaptic terminal resulting in reduced exocytosis of acetylcholine containing vesicles. Consequently, there will typically be not as much increase in muscle strength observed after edrophonium injection, if any with LEMS.