Influence of different fat emulsion-based intravenous formulations on the pharmacokinetics and pharmacodynamics of propofol.
OBJECTIVE
The influence of different intravenous formulations on the pharmacokinetics and pharmacodynamics of propofol was investigated using the effect on the EEG (11.5-30 Hz) as pharmacodynamic endpoint.


METHODS
Propofol was administered as an intravenous bolus infusion (30 mg/kg in 5 min) or as a continuous infusion (150 mg/kg in 5 hours) in chronically instrumented male rats. Propofol was formulated as a 1% emulsion in an Intralipid 10%-like fat emulsion (Diprivan-10, D) or as a 1%- or 6% emulsion in Lipofundin MCT/LCT-10% (P1% and P6%, respectively). EEG was recorded continuously and arterial blood samples were collected serially for the determination of propofol concentrations using HPLC.


RESULTS
Following bolus infusion, the pharmacokinetics of the various propofol emulsions could adequately be described by a two-compartmental pharmacokinetic model. The average values for clearance (Cl), volume of distribution at steady-state (Vd,ss) and terminal half-life (t1/2, lambda 2) were 107 +/- 4 ml/min/kg, 1.38 +/- 0.06 l/kg and 16 +/- 1 min, respectively (mean +/- S.E. n = 22). No significant differences were observed between the three propofol formulations. After continuous infusion these values were 112 +/- 11 ml/min/kg, 5.19 +/- 0.41 l/kg and 45 +/- 3 min, respectively (mean +/- S.E., n = 20) with again no statistically significant differences between the three propofol formulations. Comparison between the bolus- and the continuous infusion revealed a statistically significant difference for both Vd,ss and t1/2, lambda 2 (p < 0.05), whereas Cl remained unchanged. In all treatment groups infusion of propofol resulted in a burst-suppression type of EEG. A profound hysteresis loop was observed between blood concentrations and EEG effect for all formulations. The hysteresis was minimized by a semi-parametric method and resulted in a biphasic concentration-effect relationship of propofol that was described non-parametrically. For P6% a larger rate constant onset of drug effect (t1/2,keo) was observed compared to the other propofol formulations (p < 0.05).


CONCLUSIONS
The pharmacokinetics and pharmacodynamics of propofol are not affected by to a large extent the type of emulsion nor by the concentration of propofol in the intravenous formulation.
Cox
E H
EH
Division of Pharmacology, University of Leiden, Sylvius Laboratory, The Netherlands.
Knibbe
C A
CA
Koster
V S
VS
Langemeijer
M W
MW
Tukker
E E
EE
Lange
R
R
Kuks
P F
PF
Langemeijer
H J
HJ
Lie-A-Huen
L
L
Danhof
M
M
D018686:Anesthetics, Intravenous / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D000818:Animals; D004338:Drug Combinations; D004569:Electroencephalography / Q000187:drug effects; D005217:Fat Emulsions, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D007262:Infusions, Intravenous; D008297:Male; D015233:Models, Statistical; D010743:Phospholipids / Q000494:pharmacology; D015742:Propofol / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013012:Sorbitol / Q000494:pharmacology; D018709:Statistics, Nonparametric
D018686:Anesthetics, Intravenous; D004338:Drug Combinations; D005217:Fat Emulsions, Intravenous; D010743:Phospholipids; C008288:Lipofundin; D013012:Sorbitol; D015742:Propofol