FENTANYL PRETREATMENT DOES NOT AFFECT THE PHARMACOKINETIC PROFILE OF AN INDUCTION DOSE OF PROPOFOL IN ADULTS

The initial disposition of propofol was reported to change when the ad ministration was preceded by fentanyl. The pharmacokinetic profile of the induction dose of propofol (2 mg kg-1 body weight) was studied in 20 ASA I patients randomly allocated to receive fentanyl 1.5 ug kg-1 ( n=12) or not (n=8). Anaesthesia was maintained with isoflurane in N2O/ O2. Venous blood drawn from the contralateral arm was used to determin e whole blood propofol concentrations. The mean propofol blood concent rations were comparable in the two groups and were best fitted by a th ree exponential equation in all the patients, conforming to a three-co mpartment open mammillary model. Distributions (T1/2alpha) redistribut ion (T1/2(7)) and elimination (T1/2beta half-lives were comparable in the groups, without significant differences in the total body clearanc e in the area under the time-concentration curve (zero-infinity) in th e volume of distribution at steady-state, in the volume of distributio n during the elimination phase or in the mean resident time. Our data support the conclusion that pretreatment with fentanyl does not affect the pharmacokinetic profile of the induction dose of propofol in ASA I patients.