Several 5-(4-arylpiperazin-1-yl)-4-benzyl-1, 2-oxazin-6-ones have been synthesized and tested for analgesic activity in a visceral pain model (phenylbenzoquinone-induced writhing test= PBQ test). A good correlation has been found between the antinociceptive effects of drugs and both their lipophilic and steric properties. The most active derivatives 5c and 5f, with intraperitoneal ED 50 values of 10.5 and 10.3 mg kg-1 respectively, were more ...