Stereoselective inhibition of monoamine oxidase and semicarbazide-sensitive amine oxidase by 4-dimethylamino-2,alpha-dimethylphenethylamine (FLA 336).

The in vitro inhibition by amiflamine [FLA 336(+)] and related compounds of the activity of rat monoamine oxidase (MAO) -A and -B, rat semicarbazide sensitive amine oxidase (SSAO) and human platelet poor plasma benzylamine oxidase was studied. Amiflamine was an MAO-A selective inhibitor, but also inhibits SSAO with both a reversible (competitive, Ki = 200 mumol/l) and a small time-dependent component which was irreversible in nature. The optical isomer FLA 336(-) was ten times less potent towards MAO-A. However, this compound was much more potent an inhibitor of SSAO (competitive, Ki = 4.6 mumol/l). The amiflamine metabolites FLA 788(+) and FLA 668(+) inhibited SSAO, but only at concentrations considerably higher than required for MAO-A inhibition. Ex vivo experiments indicated that there was no significant irreversible inhibition of rat heart and lung SSAO after both single and repeated administration of amiflamine at doses up to 20 times higher than required for inhibition of MAO-A within central serotoninergic neurones.