The present invention discloses novel compounds of general formula (I) ##STR00001## or a pharmaceutically acceptable salt or prodrug thereof (in which X.sub.1-X.sub.5, R.sub.5-R.sub.8b, Z.sub.1-Z.sub.2 and Ar.sub.1 are defined herein), a method for inhibiting the VR1 receptor in mammals using these compounds, a method for controlling pain in mammals, and pharmaceutical compositions including those compounds and a process for making those compounds.