The clinical value and the sensitivity of saliva caffeine clearance measurement was evaluated as an indicator of liver metabolic capacity in patients with primary biliary cirrhosis (PBC). Saliva test was performed in 12 female patients with PBC and 8 healthy female volunteers. After a 48 hour caffeine exclusion period two doses of 140 mg of caffeine separated by a 4 hour interval were administered orally. Saliva samples were taken 6 and 14 hours later. Caffeine concentrations were measured by high-performance liquid chromatography. Pharmacokinetic parameters were calculated by the fitting procedure of the Bayesian feedback method. There was a significant increase of caffeine half-life in patients with PBC with the mean (SD) value of 5.47 (1.33) hours as compared to that in healthy controls - 4.5 (0.69) hours. The correlation between the pharmacokinetic parameters of caffeine (half-life, clearance and volume of distribution) was statistically significant (p < 0.05) both with the prothrombin ratio and staging, based on morphologic findings in the PBC group. There was no significant correlation neither between the pharmacokinetic parameters of caffeine and conventional liver function tests, nor between the pharmacokinetic parameters and galactose elimination capacity (GEC). Our results suggest that caffeine clearance, like GEC, quantitates a very particular enzymatic reaction which may not be representative for the functional capacity of the entire organ. Thus, a simplified caffeine clearance test represents a helpful additional criterion for the assessment of hepatic function in patients with PBC.

Keywords: primary biliary cirrhosis, caffeine clearance, Bayesian estimate