mu-Opioid/5-HT4 dual pharmacologically active agents-efforts towards an effective opioid analgesic with less GI and respiratory side effects (Part I).

Novel compounds were prepared that united the pharmacologies of the mu-opioid tramadol with the 5-HT4 agonists metoclopramide and norcisapride. The synthesis, chiral separation and in vitro activity of the new compounds is described.