Naltrexone fails to antagonize the sigma effects of PCP and SKF 10,047 in the dog.

SKF 10,047, N-allylnormetazocine, a benzomorphan narcotic antagonist, and the arylcyclohexylamine anesthetic phencyclidine produced similar reflex, autonomic and behavioral effects in the chronic spinal dog which were not antagonized by naltrexone pretreatment. Naltrexone did effectively prevent the effects of morphine. These data provide further evidence that the acute effects of phencyclidine and SKF 10,047 are alike and that their principal mechanism of action does not involve opiate activity of the morphine type.