α-Methylserotonin (αMS), also known as α-methyl-5-hydroxytryptamine (α-methyl-5-HT) or 5-hydroxy-α-methyltryptamine (5-HO-αMT), is a tryptamine derivative closely related to the neurotransmitter serotonin (5-HT).

[1] In addition to its actions at the serotonin receptors, αMS has been found to act as a norepinephrine releasing agent similarly to α-methylphenylalanine and to other α-alkylated tryptamines.

[3][4][5] Unlike serotonin, αMS is not metabolized by monoamine oxidase on account of the α-methyl substituent blocking the enzyme's access to the amine.

[6][7] Similarly to serotonin however, αMS poorly crosses the blood-brain-barrier due to its free hydroxyl group, and thus has only weak or no central effects when administered peripherally.

[8] αMS is not scheduled at the federal level in the United States,[9] but it could be considered an analogue of α-methyltryptamine (AMT), in which case, purchase, sales, or possession could be prosecuted under the Federal Analog Act.