Fig. 1. Pain intensity (0–10 verbal score; left ) or pain affective magnitude (0–30.2 arbitrary units; right ) before and after intravenous administration of butorphanol (But), meperidine (Mep), or their combination (Both). Each bar represents the mean ± SEM of 15 subjects. * P < 0.05 compared with predrug value within groups. Groups do not differ before or after drug administration .