4-MTA

4-methylthioamphetamine is a drug known as 4MT, 4-MTA, "Flatliners" or 1-(4-methylthiophenyl)-2-aminopropane. It was developed by the research team led by David E. Nichols, but was intended to be used only as an agent for laboratory research into the serotonin transporter protein, and Nichols was reportedly horrified when 4-MTA appeared as a drug of abuse on the street. 4-MTA is currently a Class A drug in the United Kingdom although it has been suggested it be rescheduled as a Class B drug.

4-MTA is a stimulant and strong serotonin releaser, similar to paramethoxyamphetamine but more dangerous, as it can cause pronounced hyperthermia which can result in organ failure and death. The subjective effects of 4-MTA are primarily a long-lasting stimulant, with little euphoria. 4MT is also a MAO-A inhibitor, which may explain its tendency to cause death, as MAOI drugs are not generally considered safe to use with stimulants or serotonin releasers, and 4-MTA fits into all three categories. 4-MTA was briefly sold on the black market as MDMA during the late 1990s, mainly in Holland and the USA, but proved unpopular due to its high risk of severe side effects (several deaths were reported) and relative lack of positive MDMA-like euphoria.