Edrophonium

Edrophonium, formerly sold under the brand name Tensilon among others, 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.

Edrophonium

Clinical data
Trade names	Tensilon, Enlon
AHFS/Drugs.com	FDA Professional Drug Information
ATC code	V04CX07 (WHO)
Legal status
Legal status	US: Discontinued
Pharmacokinetic data
Duration of action	10–30 minutes
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
CompTox Dashboard (EPA)	DTXSID4046943
Chemical and physical data
Formula	C10H16NO+
Molar mass	166.244 g·mol−1
3D model (JSmol)	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?)  (verify)

Medical uses

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— reduces 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 ancetylcholinesterase 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. However, the edrophonium and ice pack tests are no longer recommended as first-line tests due to false positive results. In practice, the edrophonium test has been replaced by testing for autoantibodies, including acetylcholine receptor autoantibodies and muscle specific tyrosine kinase autoantibodies.^[1][2]

The Tensilon test may also be used to predict if neurotoxic paralysis caused by snake envenomation is presynaptic or postsynaptic. If it is postsynaptic, then paralysis will be temporally reversed, indicating that can be reversed by adequate antivenom therapy. If the neurotoxicity is presynaptic, then the Tensilon test will show no response and antivenom will not reverse such paralysis. In this instance reversal of paralysis will not occur until the damaged terminal axons at the neuromuscular junction have recovered, this may take days or weeks.^[3]

The drug may also be used for reversal of neuromuscular blockade at the end of a surgical procedure.^[4]

Chemistry

Edrophonium, ethyl-(3-hydroxyphenyl)dimethylammonium chloride, is made by reacting 3-dimethylaminophenol with ethyl bromide, which forms ethyl(3-hydroxyphenyl)dimethylammonium bromide, the bromine atom of which is replaced with a chlorine atom by reacting it with silver chloride, giving edrophonium.^[5]

Pharmacokinetics

The drug has a brief duration of action, about 10–30 mins.^[4]