2-Fluoroamphetamine (2-FA) is a stimulant drug from the amphetamine family which has been sold as a designer drug. 2-Fluoroamphetamine differs from 3- and 4-fluoroamphetamine in the position of the fluorine atom on the aromatic ring, making them positional isomers of one another. The replacement of a hydrogen atom with a fluorine atom in certain compounds to facilitate passage through the blood–brain barrier, as is desirable in central nervous system pharmaceutical agents, is a common practice due to the corresponding increase in lipophilicity granted by the substitute.