Abstract
During long-term administration of slow-release oral morphine, plasma concentrations of morphine (M), morphine-3-glucuronate (M3G) and morphine-6-glucuronate (M6G) were analyzed. A 75-year-old woman with lung cancer received 120mg of slow-release oral morphine twice a day for 30 weeks. The patient obtained good pain control without adverse effects during this period. At the same time, weekly blood samples were collected just before morphine administration. Plasma M concentration varied between 12 and 45ng/ml and seemed to decrease gradually during the course of that period. Both plasma concentrations of M3G and M6G were linearly related to that of the morphine.
These results indicate that plasma concentrations of morphine and morphine metabolites change variably even in the state of good pain control during long-term administration of slow-release oral morphine.
