Ursodiol: a cholesterol gallstone solubilizing agent.

Ursodiol, a naturally occurring bile acid, has gained Food and Drug Administration approval for the dissolution of cholesterol gallstones. Ursodiol inhibits hepatic cholesterol synthesis and secretion. Lithocholic acid, a potentially hepatotoxic metabolite of ursodiol and chenodiol, may accumulate to a lesser extent with ursodiol than with chenodiol. Enterohepatic recirculation of ursodiol and its metabolites occurs and is essential to the dissolution of cholesterol gallstones. Complete dissolution has been achieved in 17 percent of patients with noncalcified, radiolucent, floating, cholesterol gallstones. Recurrence of cholesterol gallstones may occur in over one-half of initial responders. Diarrhea reported in up to 50 percent of the patients on chenodiol has been reported in only 4 percent of patients treated with ursodiol. Increased mean aspartate aminotransferase levels to more than twice the pretreatment level seen with chenodiol therapy have not been reported with ursodiol. Reportedly fewer adverse reactions may give ursodiol a major advantage over chenodiol in hospital formulary considerations.