Comparison of analgesic effect of oxycodone and morphine on patients with moderate and advanced cancer pain: a meta-analysis

BACKGROUND: Morphine and oxycodone are considered as wide-spreadly used opioids for moderate/severe cancer pain. However, debate exists about the evidence regarding their relative tolerability and underlying results. METHODS: A systematic search of online electronic databases, including PubMed, Embase, Cochrane library updated on October 2017 were conducted. The meta-analysis was performed including the studies that were designed as randomized controlled trials. RESULTS: In total, seven randomized clinical trials met our inclusion criteria. No statistical differences in analgesic effect between oxycodone and morphine were observed. Both the pooled analysis of API (MD =0.01, 95% CI -0.22 – 0.23; p = 0.96) and WPI (MD = − 0.05, 95% CI -0.21 – 0.30; p = 0.72) demonstrated clinical non-inferiority of the efficacy of morphine compared with oxycodone, respectively. Additionally, no significant difference in PRR response was observed in either oxycodone or morphine that were used in patients (MD =0.99, 95% CI -0.88 – 1.11; p = 0.87). With the pooled result of AEs indicating the comparable safety profiles between the 2 treatment groups, the meta-analysis on the nausea (OR = 1.20, 95% CI 0.90–1.59; p = 0.22), vomiting (OR = 1.33, 95% CI 0.75–2.38; p = 0.33), somnolence (OR = 1.35, 95% CI 0.95–1.93; p = 0.10), diarrhea (OR = 1.01, 95% CI 0.60–1,67; p = 0.98), and constipation (OR = 1.04, 95% CI 0.77–1.41; p = 0.79) was conducted, respectively. CONCLUSIONS: In the current study, no remarkable difference was identified either in analgesic efficacy or in tolerability of oxycodone and morphine as the first-line therapy for patients with moderate to severe cancer pain. Thus, no sufficient clinical evidence on the superior effects of oxycodone to morphine was provided in this experimental hypothesis.