Biliary excretion of xenobiotics is a complex process involving uptake into liver, intracellular sequestration and/or biotransformation, and transport into bile. A description of liver morphology is included to aid in the understanding of how chemical and physiological factors affect hepatic uptake and biliary excretion. Data will be presented with morphine and nalorphine that illustrate how efficient the intestinal and hepatobiliary system is in clearing drugs from the body. However, enterohepatic circulation can interfere with these processes.
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