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Enterohepatic circulation

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  p16-17

2026-09-13

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Enterohepatic circulation

Drugs and metabolites present in the liver are often also excreted into bile. These pass into the jejunum and may be reabsorbed or passed into the faeces. The process of biliary excretion and reabsorption may occur a number of times before a drug is completely eliminated by the body. This recycling of drugs is known as enterohepatic circulation.

Common examples include the glucuronide conjugates of drugs such as morphine. Enterohepatic circulation prolongs the persistence of a drug in the body and may lead to delayed toxicity. Drugs that undergo enterohepatic circulation may be detected in the faeces or in gastric contents (small amounts) after reflux or vomiting, or in unchanged forms, even if administered by a parenteral route. Basic drugs (e.g. amfetamine) may also appear in the gastric contents by passive diffusion across the gastric mucosa from the blood. It is therefore important that if gastric contents are analysed and small amounts of drug are detected, these are not automatically assumed to be from oral administration.

In the absence of urine, bile can be a useful body fluid for analysis (e.g. for opioids, benzodiazepines and colchicine).