Abstract
Modes of action of codeine epoxide, a new metabolite of codeine, and epoxides of morphine and heroin on the electrically stimulated guinea pig ileum were studied. The opiates and their epoxides inhibited the twitch response of the ileum to electrical stimulation. The inhibitory actions of the test drugs were antagonized by naloxone. The activities of epoxides were not strikingly different from those of the parent opiates. Dependence liabilities of the epoxides were also tested on the guinea pig ileum which was treated with a high concentration of the test drugs. Epoxydation of 7, 8-double bond in the parent opiates showed a trend toward a decrease in dependence liability.
