BACKGROUND: Aquafol^® is a microemulsion formulation of propofol. This study was designed to investigate the population pharmacokinetic and pharmacodynamic modeling in beagle dogs sedated by Aquafol^®.

METHODS: Electroencephalogram was recorded and venous blood was sampled at preset times in 15 beagle dogs during 3 hours of infusion of Aquafol^® and subsequently during 3 hours of recovery. Venous blood was sampled at 0, 2, 10, 30, 60, 120, 180, 190, 240 and 360 minutes after infusion. We evaluated the effect of propofol on electroencephalogram by calculating SEF₉₀. In the preliminary analysis, two compartment model best described all data from all subjects. The pharmacodynamics were best described using an effect compartment model and k_e0, a first-order elimination rate constant characterizing the effect-site equivalent to estimate the apparent effect-site concentrations. The relationship between propofol effect-site concentration and SEF₉₀ was analyzed using an inhibitory sigmoid E_max model.

RESULTS: The final pharmacokinetic model was best described with the followings: V₁ = 18.5e^0.114*BWT, k₁₀ = 1.86 min^-1, k₁₂ = 0.6 min^-1, k₂₁ = 0.684 min^-1. The final pharmacodynamic model was best described with the followings: t_1/2k_e0 = 0.62 min, C_e50 = 32.2 ng/ml, E_o = 31.3 Hz, E_max = 20.9 Hz, γ = 1.28.

CONCLUSIONS: The propofol microemulsion shows different pharmacokinetics and pharmacodynamics compared with the propofol lipid emulsion.