(+)Amphetamine-stimulus generalization to an herbal ephedrine product

We have previously demonstrated that a (+)amphetamine stimulus generalizes both to (-)ephedrine and caffeine. Using rats trained to discriminate intra peritoneal (IP) administration of 1.0 mg/kg of (+)amphetamine (ED50 = 0.4 m g/kg) from saline vehicle in a standard two-lever drug discrimination proce dure, the present investigation shows that the (+)amphetamine stimulus gene ralizes to (+)amphetamine (ED50 = 1.0 mg/kg) when administered via the intr agastric (IG) route, and that (+)amphetamine appears about 2.5-fold less po tent when administered via the IG route compared to the IP route. Likewise, (-)ephedrine (ED50 = 10.8 mg/kg) and caffeine (ED50 = 32.9 mg/kg) are also 2.5-fold less potent when administered via the IG route compared to their potency when administered via the TP route. The (+)amphetamine stimulus als o generalizes to an IG-administered herbal preparation (i.e., Herbal XTC(R) ; the herbal preparation possesses an approximate potency roughly comparabl e to what might have been expected on the basis of its reported ephedrine a nd/or caffeine content. These results demonstrate, for the first time, that an ephedrine-containing herbal preparation can produce a (+)amphetamine-li ke effect in animals. (C) 2000 Elsevier Science Inc.