Maintenance of hepatic bile acid secretion rate during overnight fasting by bedtime bile acid administration.

We have tested the hypothesis that the greater clinical efficacy of bedtime administration of bile acid in gallstone dissolution is due to prevention of the reduction in hepatic bile acid secretion that normally accompanies overnight interruption of the enterohepatic circulation, thus also reducing the secretion of supersaturated hepatic bile. We measured the hepatic bile acid secretion rate by combining duodenal perfusion of a nonabsorbable recovery marker (polyethylene glycol) with continuous intravenous infusion of a hepatic bile marker (indocyanine green). We studied 6 subjects with gallstones before and during administration of ursodeoxycholic acid (UDCA, 675 mg) at bedtime. Duplicate pretreatment studies revealed good reproducibility. Mean values for hepatic bile acid secretion rate were uninfluenced by chronic UDCA administration before the acute bedtime dose, but during the 4-h period after acute administration of UDCA the total bile acids secreted increased by a mean value of 2.2 mmol (p less than 0.01). Before treatment, nine of the 78 hourly samples were secreted at a hepatic bile acid secretion rate of less than 5 mumol/kg.h in the 6 patients studied, compared with only one hourly sample during UDCA administration. Super-saturated hepatic bile was secreted for a mean of 9.5 h before treatment, and for 1.2 h during UDCA treatment (p less than 0.005). We conclude that if UDCA is administered at bedtime, this maintains the hepatic bile acid secretion rate overnight, thus reducing secretion of supersaturated hepatic bile, in addition to the well-established effect of UDCA on cholesterol secretion.