Eserine

Physostigmine

Clinical data
Trade names	Antilirium
AHFS/Drugs.com	Monograph
Pregnancy category	AU: C US: C (Risk not ruled out)
Routes of administration	intravenous, intramuscular, ophthalmic
ATC code	S01EB05 (WHO) V03AB19 (WHO)
Legal status
Legal status	US: ℞-only
Pharmacokinetic data
Metabolism	Major metabolite: Eseroline
Identifiers
IUPAC name (3aR,8aS)-1,3a,8-Trimethyl-1H,2H,3H,3aH,8H,8aH-pyrrolo[2,3-b]indol-5-yl N-methylcarbamate
CAS Number	57-47-6 Y
PubChem CID	5983
IUPHAR/BPS	6598
DrugBank	DB00981 Y
ChemSpider	5763 Y
UNII	9U1VM840SP
KEGG	D00196 Y
ChEBI	CHEBI:27953 Y
ChEMBL	CHEMBL94 Y
ECHA InfoCard	100.000.302
Chemical and physical data
Formula	C15H21N3O2
Molar mass	275.346 g/mol
3D model (Jmol)	Interactive image
SMILES O=C(Oc1cc2c(cc1)N([C@H]3N(CC[C@@]23C)C)C)NC
InChI InChI=1S/C15H21N3O2/c1-15-7-8-17(3)13(15)18(4)12-6-5-10(9-11(12)15)20-14(19)16-2/h5-6,9,13H,7-8H2,1-4H3,(H,16,19)/t13-,15+/m1/s1 Y Key:PIJVFDBKTWXHHD-HIFRSBDPSA-N Y

Physostigmine (also known as eserine from éséré, the West African name for the Calabar bean) is a highly toxic parasympathomimetic alkaloid, specifically, a reversible cholinesterase inhibitor. It occurs naturally in the Calabar bean and the Manchineel tree.

The chemical was synthesized for the first time in 1935 by Percy Lavon Julian and Josef Pikl. It is available in the U.S. under the trade names Antilirium and Isopto Eserine, and as eserine salicylate and eserine sulfate. Today, physostigmine is most commonly used for its medicinal value but before its discovery by Sir Robert Christison in 1846, it was much more prevalent as a poison. The positive medical applications of the drug were first suggested in the gold medal winning final thesis of Thomas Richard Fraser at Edinburgh University in 1862.

Physostigmine acts by interfering with the metabolism of acetylcholine. It is a covalent (reversible - bond hydrolyzed and released) inhibitor of acetylcholinesterase, the enzyme responsible for the breakdown of acetylcholine in the synaptic cleft of the neuromuscular junction. It indirectly stimulates both nicotinic and muscarinic acetylcholine receptors. Physostigmine has an LD50 of 3 mg/kg in mice.

Combination of acetylcholine and physostigmine is an example of supra-additive phenomenon .