Effect of adjuvant drugs on the analgesic activity of opioid morphine analgesics and compound RU-1205

Introduction: Adjuvant medications can be used to increase the analgesic effect of opioid analgesics, reduce the manifestation of side effects, and also for premedication. This paper provides information on the effect of clonidine, haloperidol, metocloparmide, diazepam, midazolam on opioid analgesics: - morphine and the selective kappa-opioid agonist compound RU-1205. Materials and methods: A probable interaction between RU-1205, morphine and adjuvant drugs in pain behaviors was carried out on the model of somatogenic pain. 95 male mice received either RU-1205 (5 mg/kg, i.p.) and morphine (1 mg/kg, i.p.) separately or in combination with haloperidol (0.45 mg/kg, i.p.); midazolam (0.3 mg/kg, i.p.); diazepam (1 mg/kg, i.p.); metoclopramide (5 mg/kg, i.p.), and clonidine (1 mg/kg, i.p.). The analgesic effect was assessed by tail flick test. Registration of the latent period of the reaction was carried out 30, 60 and 90 minutes after the adjuvant drug administration. Results: When studying the interaction with morphine, it was found that clonidine, haloperidol and metoclopramide enhanced the effects; diazepam offset them, and midazolam had no affect on the analgesic properties. In the course of the studies, RU-1205 showed an increase in analgesic activity when combined with clonidine, a slight increase with midazolam, and a decrease when co-administered with diazepam. Haloperidol had no influence on the effect of RU-1205, while metoclopramide both potentiated and reduced the analgesic effect. Discussion: Pharmacodynamic and pharmacokinetic interactions of RU-1205 with an α2AR agonist, benzodiazepine receptor agonists, D2P antagonist, and σ-receptor blocker were established. Conclusion: The presented data make it possible to more accurately formulate ideas about the localization and action mechanism of the kappa-agonist of opioid receptors, the compound RU-1205.