Purpose: 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. Methods: 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. Result: 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 (p＝0.007). 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. Conclusion: These results indicate that the simple conversion ratio could be safety for opioid switching between OXJ and other opioid in cancer pain treatment.

In the present study, we examined the sex-related differences and cross-sectional age-related changes in the cross-sectional area of the psoas major muscle. The cross-sectional area was corrected for fat-free mass (FFM-corrected), which was calculated as the 2/3rd power of the total fat-free mass. A total of 240 adults (114 men, 126 women, age: 20-81 years) were included in the study. The cross-sectional area of the psoas major muscle was measured by 0.2T magnetic resonance imaging (MRI), and the total fat-free mass was measured by air displacement plethysmography. We demonstrated that the FFM-corrected cross-sectional area of the psoas major muscle was greater in males than females across all age groups. Furthermore, we examined the mean FFM-corrected cross-sectional area of the psoas major muscle across different age groups and demonstrated that it decreased with age. Our findings, when combined with previous results, show a peak in the 20s, which declined with age. Our study revealed sex-related differences and cross-sectional age-related changes in the FFM-corrected cross-sectional area of the psoas major muscle. Our findings also suggest that it is important to define reference values and ranges that take into account age- and sex-related differences when assessing the psoas major muscle by FFM-corrected cross-sectional area.