Analgesic and tolerance studies with AP-237, a new analgesic.

1-n-Butyryl-4-cinnamylpiperazine hydrochloride, AP-237, is a new analgesic that has been reported in both Japan and the United States to have good analgesic activity in animals and is currently undergoing clinical trials. A detailed study of the analgesic and side effect profile of this compound is presented. AP-237 was an effective analgesic in a variety of species by several different routes of administration. Results of studies in an inflamed paw pressure and tail flick test in rats, hot plate and writhing test in mice, tooth pulp test in rabbits and intra-arterial bradykinin test in dogs are reported. AP-237 had a low physical dependence liability in rodents as measured by a mouse jumping test and a lack of withdrawal syndrom. Tolerance and cross tolerance results are reported. AP-237 is compared to morphine and pentazocine in most tests.