Sympathomimetic drugs are substances that mimic the effects of the hormone epinephrine (adrenaline) and the hormone/neurotransmitter norepinephrine (noradrenaline). They all raise blood pressure and are all weak bases.
Classical sympathomimetic drugs are amphetamines (including MDMA), ephedrine and cocaine, which act by blocking and reversing norepinephrine transporter (NET) activity. NET is a transport protein expressed on the surface of some cells that clears noradrenaline and adrenaline from the extracellular space and into cells, terminating the signaling effects.
Substances like cocaine also affect dopamine, and some substances like MDMA affect serotonin.
Norepinephrine is synthesized by the body into epinephrine, causing central nervous system stimulation. Thus, all sympathimimetic amines fall into the larger group of stimulants (see psychoactive drug chart). Many of these stimulants have therepeutic use and abuse potential, can induce tolerance, and possibly physical dependence.