Gender differences in the pharmacokinetics of propofol in elderly patients during and after continuous infusion

Differences in the pharmacokinetics of propofol between male and female patients during and after continuous infusion have not been described in detail in patients aged 65 yr and older. To increase our insight into the pharmacokinetics of propofol in this patient population and to obtain pharmacokinetic parameters applicable in target controlled infusion (TCI), the pharmacokinetics of propofol during and after continuous infusion were studied in 31 ASA class 1 and 2 patients, aged 65–91 yr, scheduled for general surgery. Patients received propofol 1.5 mg kg−1 i.v. in 1 min followed by 7 mg kg−1 h−1 until skin closure in the presence of a variable rate infusion of alfentanil during oxygen–air ventilation. On the basis of arterial blood samples that were taken up to 24 h post-infusion, the pharmacokinetics of propofol were evaluated in a two-stage manner. Multiple linear regression analysis was used to explore the effect of age, weight, gender and lean body mass as covariates. Gender significantly affected the pharmacokinetics of propofol. V3, Cl1 and Cl2 were significantly different between male and female patients, weight only affected Cl1. The pharmacokinetic parameters were: V1=4.88 litre, V2=24.50 litre, V3 (litre)=115+147×gender (gender: male=1, female=2), Cl1 (litre min−1)=–0.29+0.022× weight+0.22×gender, Cl2 (litre min−1)=2.84–0.65×gender (male=1, female=2), and Cl3=0.788 litre min−1.