ABSTRACT
<b>Purpose:</b> The simple conversion ratio of 1：1：1/50 between oxycodone injection (OXJ), morphine injection and fentanyl injection is used at Saga－Ken Medical Centre Koseikan. However, there are no studies on the validity of the simple conversion ratio. <b>Methods:</b> A total of 18 patients with opioid switching to OXJ using the simple conversion ratio were reviewed in this investigation. We surveyed the change in the numeric rating scale (NRS) and adverse effects before and after opioid switching. <b>Result:</b> The average period needed to reach a stable dose of OXJ was 0.6 days. The reasons of opioid switching to OXJ were the uncontrolled cancer pain in 11 patients, the impossibility of oral administration in 6 patients, the drowsiness in 1 patient. The average NRS decreased from 3.3 to 1.1 in 11 patients with uncontrolled cancer pain <i>(p＝0.007)</i>. No obvious change in the NRS was observed in 6 patients with the impossibility of oral administration. In 18 patients, there was no significant difference in adverse effects before and after opioid switching. <b>Conclusion:</b> These results indicate that the simple conversion ratio could be safety for opioid switching between OXJ and other opioid in cancer pain treatment.