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. 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 activat