Pharmacokinetic interaction of propofol and fentanyl: single bolus injection study

The effect of pretreatment with fentanyl on the pharmacokinetics of a single bolus of propofol was studied in 17 female patients (mean age 35 yr), ASA grade I. Eight patients received fentanyl 1.5 micrograms kg-1 5 min before induction of anaesthesia. In all patients anaesthesia was induced with propofol 2.5 mg kg-1 and maintained with halothane and nitrous oxide in oxygen. Pretreatment with fentanyl resulted in prolonged apnoea in all eight patients compared with three of nine patients in the control group. The pharmacokinetic values for propofol were described by a three-compartment mammillary model with rapid distribution phases (T1/2 alpha mean (SEM) 3.1 (2.0) min and T1/2 beta 44 (9.1) min) and a slower final phase of T1/2 gamma 520 (96) min. The clearance of propofol was rapid (mean 1.6 (0.24) litre min-1). Propofol was distributed initially into a relatively large central compartment (mean 23.7 (6.6) litre) and was extensively redistributed (mean Vss 593 (157) litre). There was no difference in the pharmacokinetic profile of propofol between the two groups.