Efficacy and Safety of Oxycodone Injection for Relieving Cancer Pain: A Study in Japan Consisting of Two Open Trials for Intravenous and Subcutaneous Administration

Abstract

Pure oxycodone injection became increasingly necessary after oral oxycodone was launched in Japan in 2003. However, trials clarifying the efficacy and safety of injection are rare. Therefore, a multicenter open study on injection was designed and carried out in 2010, resulting in the launch of injection therapy in 2012. As published domestic case reports on efficacy already show widespread prescription, this study aimed to provide useful information for cancer pain relief in Japan and other countries. Our oxycodone injection study consisted of two trials, one of intravenous (S#9131) and the other of subcutaneous (S#9132) administration. The minimum required number of enrolled patients suffering cancer pain was determined to be 70 in S#9131 and 20 in S#9132. These studies had the same dose-titration protocol as the main endpoint, i.e., pain relief rate (PRR) defined as the rate of achieving adequate pain control (APC), as in prior oral oxycodone trials in Japan. In S#9131, PRR was 81.4% (95% confidence interval: 70.3-89.7%), therefore, the null hypothesis of PRR<70% was rejected using the binominal one-sided test (p=0.0217). In S#9132, PRR was 73.7% also surpassing 70%. Safety was also assessed in the same way as in prior trials. The majority of adverse effects were moderate or mild and recovered with no sequelae. As shown above, the injection was considered to be effective and safe in cancer pain treatment. The details of these trials, particularly the dose-titration protocol for achieving APC and route switching information, are expected to enhance injection convenience for prescribers.

Keywords: cancer pain; opioid switching; oxycodone; pain management; route switching.