Oxycodone is a semi-synthetic opioid that is effective in alleviating cancer-related pain, post-operative pain, osteoarthritis and neuropathic non-malignant pain (25
). In 2001, oxycodone was suggested as one alternative to morphine in the WHO and the European Association for Palliative Care (EAPC) recommendations (26
). During the past decade, oxycodone has still been considered as a step II opioid, or as a constituent of compound preparations with a non-opioid analgesic in China. However, the use of oxycodone has increased significantly in China (27
). The clinical efficacy of oxycodone is similar to that of morphine sulfate, codeine and tramadol, but oxycodone is more potent with an equianalgesic ratio of 1/1.5–2 (28
). Common side-effects of oxycodone are nausea, constipation, dizziness, vomiting, sleepiness, pruritus, anorexia and dysuria (29
). In severe cases, intoxication coma, pulmonary edema and circulatory failure may appear and cause mortality (30
). The aim of this study was to provide evidence-based guidelines on a wide variety of issues relevant to the use of oxycodone in cancer patients with moderate-severe cancer-related pain in China.
This meta-analysis was the first study to evaluate the differences between oxycodone and other strong opioids in moderate-severe cancer-related pain in China and may be able to add more information regarding this question. In this meta-analysis, we quantitatively assessed the differences in the efficacy and tolerability of oxycodone and other strong opioids in moderate-severe cancer-related pain in China. Finally, seven RCTs were included with a total of 613 cancer patients with moderate-severe pain. The meta-analysis results showed that oxycodone was statistically superior to other strong opioids in pain intensity scores following intervention and the differences between them were statistically significant. However, there was no significant difference between oxycodone and other strong opioids in pain intensity scores prior to intervention. In addition, there were statistically significant differences between oxycodone and other strong opioids for cancer-related pain on the obvious effective rate and overall effective rate. Compared with other strong opioids, nausea and constipation occurred significantly less with the use of oxycodone for cancer-related pain. There was no difference between oxycodone and other strong opioids in six other common side-effects, including dizziness, vomiting, sleepiness, pruritus, anorexia and dysuria. Publication bias of the literature was assessed by Begg’s funnel plot and Egger’s linear regression test. No statistical significance for all evaluations of publication bias was found.
Similar to other meta-analyses, a number of limitations of this study should be addressed. First of all, a meta-analysis is a type of retrospective study and is limited by the quality of the primary studies. Secondly, although a perfect searching strategy was designed prior to initiating this study, and computerized and manual searching were performed simultaneously, there is a possibility that suitable studies were not included. Thirdly, although we defined strict inclusion criteria, there may be potential studies that were not included in this meta-analysis due to incomplete raw data. Although we actively contacted the authors, they did not provide a comprehensive set of data. Most importantly, this meta-analysis was based on unadjusted data, and the main confounding variables were not available in the original papers and could also not be quantitatively analyzed.
In conclusion, our meta-analysis of seven RCTs demonstrated that the efficacy and tolerability of oxycodone are superior to other strong opioids, including morphine sulfate, codeine and tramadol, supporting its use as an opioid for cancer-related pain in China. As few studies are available in this field and current evidence remains limited, this conclusion should be further confirmed by large case-control studies with an adequate methodological quality and proper controlling for possible confounding factors.