<unk> , a sympathomimetic amine, acts on part of the sympathetic nervous system (SNS). The principal mechanism of action relies on its indirect stimulation of the adrenergic receptor system by increasing the activity of norepinephrine at the postsynaptic α and β receptors. The presence of direct interactions with α receptors is unlikely, but still controversial. L-ephedrine, and particularly its stereoisomer norpseudoephedrine (which is also present in Catha edulis) has indirect sympathomimetic effects and due to its ability to cross the blood-brain barrier, it is a CNS stimulant similar to amphetamines, but less pronounced, as it releases noradrenaline and dopamine in the substantia nigra. The presence of an N-methyl group decreases binding affinities at α receptors, compared with norephedrine.<unk> , though, binds better than N-methylephedrine, which has an additional methyl group at the nitrogen atom. Also the steric orientation of the hydroxyl group is important for receptor binding and functional activity. ;Compounds with decreasing α-receptor affinity RS-Norephedrine.Norephedrine RS-Ephedrine.Ephedrine RS-N-Methylephedrine.N-Methylephedrine
Ephedrine
Pseudoephedrine
Tesofensine
Eptazocine
Dezocine
Naloxone
Butalbital
Bremazocine