4-Methylamphetamine (4-MA; PAL-313; Aptrol ; p-TAP) is a stimulant and anorectic drug of the phenethylamine and amphetamine chemical classes.

In vitro, it acts as a potent and balanced serotonin, norepinephrine, and dopamine releasing agent with Ki affinity values of 53.4nM, 22.2nM, and 44.1nM at the serotonin, norepinephrine, and dopamine transporters, respectively.[1] However, more recent in vivo studies that involved performing microdialysis on rats showed a different trend. These studies showed that 4-methylamphetamine is much more potent at elevating serotonin (~18 x baseline) relative to dopamine (~5 x baseline). The authors speculated that this is because 5-HT release dampens DA release through some mechanism. For example, it was suggested that a possible cause for this could be activation of 5HT2C receptors since this is known to inhibit DA release. In addition there are alternative explanations such as 5-HT release then going on to encourage GABA release, which has an inhibitory effect on DA neurons.[2]

4-MA was investigated as an appetite suppressant in 1952 and was even given a trade name, but development was apparently never completed.[3] More recently it has been reported as a novel designer drug.

In animal studies, 4-MA was shown to have the lowest rate of self-administration out of a range of similar drugs tested (the others being 3-methylamphetamine, 4-fluoroamphetamine, and 3-fluoroamphetamine), likely as a result of having the highest potency for releasing serotonin relative to dopamine.[4][5]

See also