Model to study long-term effects of propoxyphene napsylate (darvon-N) on narcotic-dependent mice

Five different strains of mice were investigated for their suitability to serve as models for the study of long-term effects of propoxyphene napsylate (PN) on narcotic-dependent mice. The NIH/Swiss outbred strain proved to be most suitable because of its high liability to manifest physical dependence on morphine. Following removal of subcutaneously-implanted morphine pellets from the mice, the incidence of spontaneous withdrawal jumping was used as a quantifiable criterion of physical dependence. An orally administered suspension of PN suppressed the withdrawal jumping in a dose-dependent manner. However, chronic (daily) administration of PN at doses high enough to prevent withdrawal jumping was characterized by a high degree of toxicity.