Para-Chloromethamphetamine

para-Chloromethamphetamine (also known as 4-chloromethamphetamine and 4-CMA; code name Ro 4-6861) is a stimulant that is the N-methyl derivative and prodrug of the neurotoxic drug para-chloroamphetamine (4-CA). It has been found to decrease serotonin in rats. Further investigation into the long-term effects of chloroamphetamines discovered that administration of 4-CMA caused a prolonged reduction in the levels of serotonin and the activity of tryptophan hydroxylase in the brain one month after injection of a single dose of the drug.

Another study on rats found that 4-chloromethamphetamine was more potent at inducing conditioned taste aversion than methamphetamine.

4-Chloromethamphetamine was further investigated in the 1960s along with 4-CA and it was noted that they differed from their parent amphetamine and methamphetamine substances by exhibiting only a slight central stimulant effect in both animals and humans and that they acted like antidepressants rather than stimulants.

Studies in the 1970s found that a single dose of 10 mg/1 kg 4-CMA resulted in a decreased level of 5-hydroxytryptamine in the brain for several weeks.

4-Chloromethamphetamine was identified outside of the laboratory for the first time at the Tomorrowland festival edition 2015, where a tablet was found in possession of a drug dealer (see picture). In the following year, tablets with 4–CMA were also found in Romania, Austria and Croatia. Fortuitously, and for unknown reasons, 4-CMA disappeared briefly from the European rave scene after the Spring of 2016. However, a 2019 study of participants of a dance music festival in Belgium reported detection of 4-CMA in pills (out of 178 analyzed samples only one was mostly 4-CMA, while in one other 4-CMA was a minor ingredient).