Male and female Hairless IAF and Hartley guinea pigs: For i.v. bolus experiments, a dose of 1 mg/kg for both bupropion (BUP) and hydroxybupropion (BUPOH) were infused over a period of 30 s. For transdermal delivery, the developed TTS patches (two patches, 14.5 cm2 diffusional area) were applied to the dorsal region of the hairless guinea pigs. Blood samples were obtained for 48 h while patches were on the animal, and for another 48 h after patches were removed. Blood samples were obtained for 72 h following intravenous administration

Bupropion analogs were evaluated in neurotransmitter uptake assays using synaptosomes prepared from rat brain (adult male Sprague-Dawley rats weighing 250g). Because no significant differences between rat and human synaptosomes were observed in studies of monoamine uptake data obtained using rat tissue should predict the behavior of these compounds at the corresponding human transporter. Bupropion is a relatively weak inhibitor of DA uptake with an IC50 of 550 nM, and it is even less potent as an inhibitor of NE reuptake. Compared with bupropion, its racemic hydroxyl metabolite produces equal inhibition of NE reuptake and much weaker inhibition of DA uptake. The (2S,3S isomer is the active form ), whereas the(2S,3R) isomer shows no significant inhibition of either DA or NE uptake. Compared with bupropion, (2S,3S)-hydroxybupropion produce similar or stronger inhibition of DA and NE uptake, respectively.