Binding of propofol to human serum albumin.

The binding properties of the short-acting hypnotic agent propofol (CAS 2078-54-8) to human serum albumin were studied in vitro. Using centrifugation through ultrafiltration membranes the ratio of free and bound propofol as a function of the human serum albumin concentration was determined. In addition, a biomathematical approach was tested that allowed the determination of the number of binding sites from the measured binding profile. At a total propofol concentration of 8.81 +/- 0.25 microg/mL the concentration of the free fraction of propofol ranged from 338 +/- 11 ng/mL (mean +/- SE) at an albumin concentration of 0.5% to 15 +/- 2 ng/ mL at an albumin concentration of 8.0%. The corresponding percentage of propofol binding ranged from 96.07 +/- 0.14% to 99.83 +/- 0.02%. From this binding profile the binding site was estimated to be n(0) = 2. The measured influence of the albumin concentration on propofol binding might be of relevance in states of hypo- or hyperalbuminaemia which could result in an altered demand of propofol.