The absorption and excretion of carbenoxolone in man

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Abstract
Blood, urine and bile concentrations of carbenoxolone have been measured after oral dosage to patients. The compound is rapidly absorbed attaining high blood concentrations and, as with rats, is excreted mostly in the bile, with only traces (2% of the dose) appearing in the urine. Blood concentrations of the drug generally exhibit two maxima, at 1–2 and 3–6 h after dosage, which are taken to indicate enterohepatic circulation of the biliary-excreted conjugates. As absorption of orally administered carbenoxolone is so rapid and does not occur when the gastric contents have pH >2, it is inferred that the major site of absorption is the stomach. The high blood concentrations of carbenoxolone (60% of the dose present in the blood) are probably due to a high degree of binding of the drug to the plasma proteins. In contrast to the rat, in which carbenoxolone is largely hydrolysed to β-glycyrrhetic acid before absorption, in man carbenoxolone is absorbed largely unchanged and is excreted in the bile as the glucuronide. Gastric absorption of carbenoxolone may be necessary for the increased production of gastric mucus observed with the drug and hence is necessary for its gastric ulcer-healing activity.