Fig. 1. Plasma concentrations of morphine, morphine-3-glucuronide (M3G), and morphine-6-glucuronide (M6G) after administration of morphine (top) or M6G (bottom) as intravenous loading dose followed by intravenous infusion at doses targeted at plasma concentrations of 25 ng/ml (87.6 nm) morphine or 1,200 ng/ml (2,589 nm) M6G, respectively. Please note the different scaling of the ordinates.