Budesonide has been discussed as a potential treatment option in primary biliary cirrhosis (PBC). Therefore, we studied the pharmacokinetics and pharmacodynamics of budesonide in patients with PBC stage I/II and stage IV. Twelve patients with early PBC stage I/II and 7 patients with PBC stage IV under continuous treatment with ursodeoxycholic acid (UDCA) were enrolled in an exploratory trial. Each patient received oral budesonide for 3 weeks at weekly increasing dosages of 3 mg once to thrice per day. Budesonide and cortisol plasma levels, urinary cortisol excretion, serum liver tests, and immunoglobulins were determined on days 1, 7, and 21 of the study. Patients with PBC stage IV showed significantly higher peak plasma concentrations (4.9 +/- 3.5 vs. 1.5 +/- 0.4 ng/mL; P <.05) and areas under the plasma concentration-time curves (AUC) (23.2 +/- 16.8 vs. 5.1 +/- 1.4 hours. ng/mL, P <.01, total AUC extrapolated to infinity [AUC(0- infinity )]) after a single dose of 3 mg budesonide when compared with patients with PBC stage I/II. Equally, AUC of budesonide were significantly increased under a multiple dose regimen on day 21 (14.0 +/- 11.6 vs. 5.0 +/- 1.9 hours. ng/mL, P <.01, AUC at steady state from dosing time to 8 hours [AUC(ss,0-8 h)]). Higher levels of budesonide were related to a significant decrease in plasma cortisol and reduction of urinary cortisol excretion in patients with stage IV disease. Two patients with stage IV disease developed portal vein thrombosis (PVT). In conclusion, administration of budesonide leads to markedly elevated plasma levels in cirrhotic patients with PBC associated with serious adverse drug reactions. Thus, further evaluation of combined treatment with UDCA may be considered in early-stage PBC but not in cirrhotic patients with PBC.