The route of prolonged morphine administration affects the pattern of its metabolites in the urine of chronically treated patients.

Differences in the patterns of urinary morphine metabolites were determined in 15 patients after the prolonged administration of morphine via various routes (oral, subcutaneous, intravenous). The possible correlation between metabolite pattern and the route of prolonged morphine administration was investigated. It was established that the concentration ratios of the active metabolite, morphine-6-glucuronide to morphine and its inactive metabolite, morphine-3-glucuronide are significantly (p less than 0.05) higher after prolonged oral morphine treatment than after the systemic administration (subcutaneous or intravenous infusion) of morphine. It may therefore be concluded that patients receiving morphine orally produced significantly greater amounts of its pharmacologically more active metabolite than patients subjected to chronic systemic morphine treatment.