Analgesic Efficacy and Safety of Butorphanol versus Morphine in Adults: A Meta-Analysis of Randomized Controlled Trials
Background: Morphine, a reference analgesic, has been widely used for a long time, but its safety profile is unsatisfactory. Butorphanol, a partial agonist and antagonist of the mu-opioid receptor and agonist of the kappa-opioid receptor, may offer a better safety profile than morphine. Therefore, the present meta-analysis was conducted to compare the analgesic efficacy and safety of butorphanol with that of morphine.
Methods: Three electronic databases, MEDLINE, EMBASE, and Cochrane CENTRAL, were systematically searched to identify studies comparing the analgesic efficacy and safety of butorphanol with that of morphine. If heterogeneity tests revealed statistical heterogeneity, pooled analysis was conducted using a random-effects model; otherwise, a fixed-effects model was adopted. Sensitivity analysis was applied to assess the robustness of the results, and publication bias was evaluated using funnel plots and Begg’s test.
Results: Nine studies, comprising 246 patients in the butorphanol groups and 245 patients in the morphine groups, were included in the meta-analysis. Pooled analysis revealed no significant difference between the analgesic efficacy of butorphanol and morphine (risk ratio [RR] = 0.96, 95% confidence interval [CI] 0.79–1.17; P = .664). However, compared with morphine, butorphanol was associated with a lower incidence of pruritus (RR = 0.05, 95% CI 0.01, 0.17, P = .000), nausea (RR = 0.33, 95% CI 0.15–0.75, P = .008), and vomiting (RR = 0.33, 95% CI 0.12–0.95, P = .039). In contrast, the incidence of drowsiness/somnolence/sedation with butorphanol which was used was significantly higher than that with morphine (RR = 2.46, 95% CI 1.14–5.31, P = .022).
Conclusion: The analgesic efficacy of butorphanol was comparable to that of morphine. However, butorphanol offered a better safety profile than morphine in terms of pruritus, nausea, and vomiting, but was associated with a higher incidence of drowsiness/somnolence/sedation. Thus, butorphanol may be an appropriate substitute for morphine for patients with risk factors of pruritus and postoperative nausea and vomiting, and patients requiring both analgesia and sedation. Because of the limited number of the studies currently available, more research is needed.