Comparative study of 1-cyclohexyl-4-(1,2-diphenylethyl)-piperazine and its enantiomorphs on analgesic and othe pharmacological activities in experimental animals.

The analgesic activity of (+/-)-1-cycylohexyl-4-(1,2-diphenylethyl)-piperazine (MT-45) was comparable to that of morphine. The activity of the S(+)-isomer was 1.14 to 1.97 times in mice and 1.00 and 1.23 times in rats as potent as MT-45, and 18.3 to 61.6 times as potent as the R(--)isomer, which was approximately comparable to that of Spa. The hyperglycemic and miotic activities of MT-45 and its S(+)-isomer in rabbits were negligible or very low, though they showed potent morphine-like activites. On the other hand, the R(--)-isomer showed no or very weak effects on those, while Spa showed definite effects. These results suggest that the modes of action of MT-45 and its enantiomorphs are partly different from those of morphine and Spa, and it may be concluded that MT-45 belongs to a new series of compounds having a potent analgesic activity.