Abstract: Objective To investigate the analgesic effect of 10 mg and 20 mg oxycodone hydrochloride prolonged⁃release tablets as initial titration doses in patients with severe cancer pain, and the relationship between genetic polymorphisms of OPRM1 A118G and ABCB1 C3435T and the requirement for oxycodone hydrochloride prolonged⁃release tablets. Methods A total of 148 patients with severe cancer pain, who had not previously used opioids systematically and were initially treated at the Department of Medical Oncology of the People's Hospital of Guangxi Zhuang Autonomous region between January 2019 and October 2020 were selected, and randomly divided into the experimental group and the control group, with 74 patients each, using 20 mg and 10 mg oxycodone hydrochloride prolonged⁃release tablets as the initial titration dose. The pain relief rate, the completion rate of pain titration within 3 d, the requirement for oxycodone hydrochloride prolonged⁃release tablets, and adverse reactions in both groups were recorded. The requirement for oxycodone hydrochloride prolonged⁃release tablets under different genotypes was calculated. Results The pain relief rates at 1 hour and 24 hours, as well as the completion rate of pain titration within 3 days in the experimental group were significantly higher than those in the control group（90.5% vs 68.9%, P=0.001; 89.2% vs 75.7%, P=0.031; 70.3% vs 54.1%, P=0.040）. After the titration of cancer pain was stabilized, there was no statistical significance in the 24 h requirement of oxycodone hydrochloride prolonged⁃release tablets and common adverse reactions in both groups (all P>0.05). The median 24 h requirement of oxycodone hydrochloride prolonged⁃release tablets in the experimental group and the control groups were 54.62 (35.18, 105.82) mg and 62.15 (42.69, 102.79) mg, respectively. Nausea and vomiting, constipation, and dizziness were the most common adverse reactions, all of which could be alleviated with symptomatic treatment. Patients carrying AA, AG, and GG genotypes at the OPRM1 A118G site exhibited different requirements for 24 h oxycodone hydrochloride prolonged⁃release tablets (P<0.05), among which the patients carrying the GG genotype having the highest demand , while the genetic polymorphisms of ABCB1 C3435T had no significant effect on the requirement of oxycodone hydrochloride prolonged⁃release tablets in patients with severe cancer pain. Conclusions Using 20 mg oxycodone hydrochloride prolonged⁃release tablets as the initial titration dose can improve the remission rate of severe cancer pain and ensures greater safety. The OPRM1 A118G genetic polymorphism may influence the requirement for oxycodone hydrochloride prolonged⁃release tablets and could serve as a potential biomarker to guide cancer pain treatment.

Key words: Severe  cancer  pain,  Oxycodone  hydrochloride  prolonged?release  tablets,  Genetic  polymorphism,  Analgesia,  Initial  titration  dose