Plasma clearance of cholyl-lysyl-fluorescein: a pilot study in humans

Background/Aims: Cholyl-lysyl-fluorescein is a fluorescent analogue of the natural bile acid, cholyl glycine. In vivo and in vitro studies showed that this analogue has many biological characteristics similar to cholyl glycine. In this study we analysed cholyl-lysyl-fluorescein plasma clearance in six healthy volunteers as a potential quantitative liver function test. Methods: The compound in water for injection was administered as an i.v. bolus in the dose of 0.02 mg/kg b.w. Results: The plasma elimination curve showed rapid, intermediate and slow phases of clearance. Half-life (T 1 2 time) for the first (t 1 2 1st phase ), second (t 1 2 2nd phase ) and third (t 1 2 3rd phase ) phases of elimination was 1.7±0.9 min, 6.7±1.6 min and 68±17 min, respectively. Ninety-minute plasma retention (% dose/l plasma) was 2.2%. Cholyl-lysyl-fluorescein volume of distribution and residual fluorescence after 60 min were similar to the data obtained by others for natural or radiolabelled bile acids. In five out of six healthy volunteers a 25-fold higher dose of cholyl-lysyl-fluorescein (0.5 mg/kg b.w.) was injected to estimate the safety margins of the compound. This dose was eliminated at a disappearance rate similar to that of the dose of 0.02 mg/kg b.w. and did not cause any adverse reactions. Serum liver tests measured before and after injection did not change significantly. Conclusions: This study showed that cholyl-lysyl-fluorescein clearance is similar to the clearance of endogenous natural bile acids and may potentially offer a new, dynamic test of liver function.