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Title: Effects of nalfurafine on the reinforcing, thermal antinociceptive, and respiratory-depressant effects of oxycodone: modeling an abuse-deterrent opioid analgesic in rats. Author: Townsend EA, Naylor JE, Negus SS, Edwards SR, Qureshi HN, McLendon HW, McCurdy CR, Kapanda CN, do Carmo JM, da Silva FS, Hall JE, Sufka KJ, Freeman KB. Journal: Psychopharmacology (Berl); 2017 Sep; 234(17):2597-2605. PubMed ID: 28567699. Abstract: RATIONALE: Strategies to reduce the misuse of mu opioid agonists are critically needed. Previous work has shown that kappa opioid agonists can diminish the abuse-related effects and augment the antinociceptive effects of mu agonists. However, use of traditional kappa agonists is limited by their dysphoric side effects. OBJECTIVES: The current study examined the effects of nalfurafine, a clinically available atypical kappa agonist, on the reinforcing, thermal antinociceptive, and respiratory-depressant effects of oxycodone in male rats. METHODS: To determine oxycodone/nalfurafine mixture proportions to be examined intravenously across procedures, a progressive ratio (PR) self-administration procedure compared the reinforcing effects of oxycodone (56 μg/kg/inj) available alone or as a mixture with co-administered nalfurafine (0.32, 1, or 3.2 μg/kg/inj), corresponding to oxycodone/nalfurafine proportions of 175:1, 56:1, and 18:1, respectively. Next, PR and thermal antinociception dose-effect functions were each determined for oxycodone, nalfurafine, and the same oxycodone/nalfurafine mixture proportions. Finally, the respiratory-depressant effects of equi-antinociceptive doses of oxycodone, nalfurafine, and the mixtures were compared. RESULTS: Nalfurafine decreased the reinforcing effects of oxycodone, and the 18:1 mixture did not function as a reinforcer. Oxycodone and nalfurafine each produced dose-dependent antinociception, and the mixtures produced additive antinociception. In addition, antinociceptive doses of the 56:1 and 18:1 mixtures did not produce respiratory depression. CONCLUSIONS: These results suggest that nalfurafine may augment the thermal antinociceptive effects while reducing the reinforcing and respiratory-depressant effects of oxycodone.[Abstract] [Full Text] [Related] [New Search]