Monte Carlo Simulation of an Ethanol Pharmacokinetic Model

Physiologically based pharmacokinetic (PBPK) models for ethanol

Physiologically based pharmacokinetic models have been used to describe the distribution and elimination of ethanol after intravenous administration. These models have been used to estimate the ethanol infusion profile that is sufficient for achieving a prescribed breath ethanol concentration time course in individuals, providing a useful platform for several pharmacokinetic and pharmacodynamic investigations. Mathematical foundations of these models are examined, including the derivation of an explicit set of governing equations in the form of a system of nonlinear ordinary differential equations. These equations can then be used to formulate and refine parameter identification and control strategies. Finally, a framework in which models related to this model can be constructed and analyzed is described.

Ordinary differential equation models for ethanol pharmacokinetic based on anatomy and physiology

Physiologically-based pharmacokinetic (PBPK) models have been used to describe the distribution and elimination characteristics of intravenous ethanol administration. Further, these models have been used to estimate the ethanol infusion profile required to prescribe a specific breath ethanol concentration time course in a specific human being, providing a platform upon which other pharmacokinetic and pharmacodynamic investigations are based. In these PBPK models, the equivalence of two different peripheral tissue models are shown and issues concerning the mass flow into the liver in comparison with ethanol metabolism in the liver are explained.

Short-term metabolic ethanol tolerance in dogs

Metabolic ethanol tolerance was studied in a cohort of five dogs with ethanol challenge repeated weekly over a 7-week period. During the 7-week period, the area under the blood alcohol versus time curve (AUC) increased slightly while the rate of ethanol elimination also increased slightly. During the repeated ethanol dosing, ethanol absorption shifted from approximately equal absorption in the stomach and intestine to three-fold more absorption in the intestine than in the stomach. The likely cause of the shift in absorption site was probably a concomitant change in gastric emptying that occurred with repeated dosing. This shift is significant since ethanol absorption in the small intestine has been shown to be over six-fold more rapid than ethanol absorption in the stomach.

Effects of food on ethanol metabolism

The goals of the present study were (1) to obtain ethanol pharmacokinetic data from fed dogs, and (2) perform Monte Carlo simulation to determine the effect of food on pharmacokinetic model parameter values. To a cohort of five fed dogs, 1 g ethanol per km body weight was administered as a gavage of 20% w/v ethanol solution. Blood samples taken at 0, 10, 20, 30, 40, 60, 80, 100, 120, 180, 240, and 360 minutes after the dose were mixed with anticoagulant and stored on ice. Blood ethanol concentration was determined via headspace chromatograph. Monte Carlo simulation with an ethanol pharmacokinetic model was used to estimate model parameter values and parameter standard deviations by minimization of the chi-squared function. Results indicate that 50.6 +/- 21.0% of the ethanol dose was absorbed in the stomach, and an insignificant amount of ethanol was metabolized by gastric alcohol dehydrogenase postulated for the model. At 6 hours after the ethanol dose 59.4 +/- 21.0% of the ethanol dose was retained in the dogs' stomachs.