Alpha-methyltryptamine is a variant of tryptamine with a methyl substituent on the alpha carbon. It acts as both a MAOI (monoamine oxidase inhibitor), which is how it was first proposed to work as an anti-depressant, and as a non-selective serotonin receptor agonist. It appears to work relatively equally as a reuptake inhibitor and releasing agent of the main three monoamines (dopamine, norepinephrine and serotonin).
Despite similarities in effect to MDMA, they are not chemically closely related, with AMT having a similar relationship to tryptamine as amphetamine has to phenethylamine.
AMT is pharmacologically active at doses as low as 5mg and it can take as long as 3 hours for the initial effects to be felt when used recreationally, meaning inexperienced users are sometimes at risk of believing the substance has not worked and re-dosing too early.