4-Methylthioamphetamine (4-MTA), also known as para-methylthioamphetamine (MTA), is a designer drug of the substituted amphetamine class developed in the 1990s by a team led by David E. Nichols, an American pharmacologist and medical chemist, at Purdue University.

[5] In both the Netherlands and Switzerland, the unknown compound was encountered in the hydrochloride salt form, and pictures of the different tablets were compared to each other.

Nichols' laboratory had published that the rats perceived the effects of 4-MTA to be like those of ecstasy, which was probably the motivation for its production and distribution to humans.

[7] Nichols also said, "I have never considered my research to be dangerous, and in fact hoped one day to develop medicines to help people.

[8] 4-MTA was briefly sold in smart shops in the Netherlands, though was soon banned by the Dutch government after serious side-effects started to emerge.

The Union of Smartshop Owners decided to leave it out of their assortment after they discovered the drug had only been tested on rats.

[10] 4-MTA is a strong serotonin releaser similar to para-methoxyamphetamine (PMA), which can cause pronounced hyperthermia potentially resulting in organ failure and death.

The symptoms of serotonin syndrome caused by 4-MTA are described in the Report on the Risk Assessment of 4-MTA Symptoms of the serotonin syndrome caused by 4-MTA [15] Another effect is the increase of the secretion of several hormones, like adrenocorticotropic hormone (ACTH), corticosterone, prolactin, oxytocin, and renin induced by 4-MTA through stimulation of serotonergic neurotransmission.

[18] The combination of serotonin release induction and MAOI activity is likely responsible for the severe serotonergic toxicity and hyperthermia that has occurred with 4-MTA.

This compound leads to bioactivation (toxification), since the metabolite increases dramatically the sensitivity to the reduction in ATP content.