Analgesic and other CNS depressive effects of dihydroetorphine

The analgesic, respiratory depressive, immobilizing effects and a cute toxicity of dihydroetorphine (DHE) have been evaluated and compared with those of morphine and etorphine (E). The minimal analgesic doses of DHE were 0.1—0.5 μg/kg in dogs (im), mice, rabbits and monkeys (sc). DHE injected sc was 6277 and 11488 times more potent than morphine, 5.5 and 2.7 times than E in mice (hot-plate method) and rabbits (K+ iontophoresis method), respectively. DHE caused a respiratory depression in the animals, but was less potent than morphine and E in rabbits. DHE, resembling morphine, caused Straub's tail and a marked increase in locomotor activity in mice, sedation in dogs and monkeys, and miosis in dogs. In contrast to morphine, DHE did not induce emesis in dogs. At high doses DHE resembled E in producing the immobilization of animals. The therapeutic index of DHE was high in animals. The effects of DHE were easily antagonized by nalorphine.