Evaluation of 'mu' versus 'kappa' receptor agonists for preemptive analgesia

Abstract

The study included 90 adult male and female patients undergoing elective abdominal surgery under general anesthesia. According to the route of drug administration (either i.v. or epidural), they were divided into two major groups (each contained 45 patients). But according to the type of administered opioid, each major group was subdivided into 3 subgroups. All patients included into the study were randomly classified and blindly injected by one of the unknown drugs. The intravenous groups were classified into: group (1) who received fentanyl 100 μg), group (2) who received nalbuphine (20 mg), and group (3) who received saline (control group). The epidural groups were classified into: group (4) who received saline (control group), group (5) who received nalbuphine (5 mg), and group (6) who received fentanyl (100 μg). The results of the study showed that opioids have significant preemptive effects compared to the control groups, whatever their type (μ or κ agonists), and whatever the route of administrations (i.v. or epidural routes). It was also observed that the μ opioid agonist fentanyl provided a better preemptive effect than the κ agonist nalbuphine. The i.v. routes indeed provided better preemptive effects than the epidural routes, but these effects were statistically slightly significant or not significant. The aims of this study were to assess the preemptive effects of opioids, to evaluate the different roles of μ and κ agonists, and lastly to assess the effect of different routes of opioid administration (i.v. versus epidural) on the preemptive response.