(±)-McN 5652 is a potent, orally active 5-HT uptake inhibitor. McN-5652 is characterized by exceptionally high potency as an inhibitor of the uptake of serotonin by rat brain synaptosomes in vitro (Ki approximately 0.6 nM) and ex vivo (ED50 approximately 2 mg/kg p.o.). (±)-McN 5652 is a potent, selective inhibitor of serotonin reuptake in mammalian brain. It potently potentiates 5-HT-induced effects in vivo following oral administration. Its biological activity resides predominantly in the (+)-enantiomer.