Figure 1. Change in mean pain scores on verbal rating scale (VRS). VRS scores were determined before and on days 3, 5, and 7 after methadone administration. Numerical rating scale (NRS) scores were converted to VRS scores as follows: NRS 0 = no pain (VRS 0), NRS 1-4 = mild pain (VRS 1), NRS > 4-7 = moderate pain (VRS 2), and NRS > 7-10 = severe pain (VRS 3).
Figure 2. Change in mean usage counts of rescue drugs. The usage count of rescue drugs was investigated before methadone administration, and on days 3, 5, and 7 after starting methadone administration. When multiple types of rescue drugs were used, the total usage counts were counted.