α-Ethyltryptamine (αET, AET), also known as etryptamine, is an entactogen and stimulant drug of the tryptamine family.

[1][5][6] It was originally developed and marketed as an antidepressant under the brand name Monase by Upjohn in the 1960s before being withdrawn due to toxicity.

[1][5][7] Side effects of αET include facial flushing, headache, gastrointestinal distress, insomnia, irritability, appetite loss, and sedation, among others.

[1][11] There has been renewed interest in αET, for instance as an alternative to MDMA, with the development of psychedelics and entactogens as medicines in the 2020s.

[1][5][4][6] αET was available pharmaceutically as the acetate salt under the brand name Monase in the form of 15 mg oral tablets.

[6] Side effects of αET at antidepressant doses have included facial flushing, headache, gastrointestinal distress, insomnia, irritability, and sedation.

[4] Additional side effects of αET at recreational doses have included appetite loss and feelings of intoxication.

[1][11][4] Rarely, agranulocytosis has occurred with prolonged administration of αET at antidepressant doses and has been said to have resulted in several cases and/or deaths.

[1][4][14] An approximate but unconfirmed 700 mg dose resulted in fatal hyperthermia and agitated delirium in one case.

[1] It is known to act as a weak partial agonist of the serotonin 5-HT2A receptor (EC50Tooltip half-maximal effective concentration > 10,000 nM; Emax = 21%).

[1][18] An IC50Tooltip half-maximal inhibitory concentration value of 260 μM in vitro and 80 to 100% inhibition of MAO-A at a dose of 10 mg/kg in rats in vivo have been reported.

[1] The relatively weak MAOI actions of αET have been considered unlikely to be involved in its stimulant, antidepressant, and other psychoactive effects by certain sources.

[1] αET has been found to produce serotonergic neurotoxicity similar to that of MDMA and para-chloroamphetamine (PCA) in rats.

[1] Originally believed to exert its effects predominantly via monoamine oxidase inhibition, αET was developed during the 1960s as an antidepressant by Upjohn chemical company in the United States under the generic name etryptamine and the brand name Monase, but was withdrawn from potential commercial use due to incidence of idiosyncratic agranulocytosis in several patients.

[1][5] αET gained limited recreational popularity as a designer drug with MDMA-like effects in the 1980s.

[1][5][6] Other synonyms of αET and/or its acetate salt include 3-(2-aminobutyl)indole, 3-indolylbutylamine, PAL-125, U-17312E, Ro 3-1932, NSC-63963, and NSC-88061, as well as its former brand name Monase.