PKQuest: a general physiologically based pharmacokinetic model. Introduction and application to propranolol.
BACKGROUND
A "physiologically based pharmacokinetic" (PBPK) approach uses a realistic model of the animal to describe the pharmacokinetics. Previous PBPKs have been designed for specific solutes, required specification of a large number of parameters and have not been designed for general use.


METHODS
This new PBPK program (PKQuest) includes a "Standardhuman" and "Standardrat" data set so that the user input is minimized. It has a simple user interface, graphical output and many new features: 1) An option that uses the measured plasma concentrations to solve for the time course of the gastrointestinal, intramuscular, intraperotineal or skin absorption and systemic availability of a drug - for a general non-linear system. 2) Capillary permeability limitation defined in terms of the permeability-surface area products. 4) Saturable plasma and tissue protein binding. 5) A lung model that includes perfusion-ventilation mismatch. 6) A general optimization routine using either a global (simulated annealing) or local (Powell) minimization applicable to all model parameters.


RESULTS
PKQuest was applied to measurements of human propranolol pharmacokinetics and intestinal absorption. A meal has two effects: 1) increases portal blood flow by 50%; and 2) decreases liver metabolism by 20%. There is a significant delay in the oval propranolol absorption in fasting subjects that is absent in fed subjects. The oral absorption of the long acting form of propranolol continues for a period of more than 24 hours.


CONCLUSIONS
PKQuest provides a new general purpose, easy to use, freely distributed www.pkquest.com and physiologically rigorous PBPK software routine.
Levitt
David G
DG
Department of Physiology, Minneapolis, MN 55455, USA. levitt@dcmir.med.umn.edu
D000042:Absorption; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003692:Delayed-Action Preparations; D004333:Drug Administration Routes; D006801:Humans; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D011433:Propranolol / Q000008:administration & dosage / Q000493:pharmacokinetics*; D014018:Tissue Distribution
D000959:Antihypertensive Agents; D003692:Delayed-Action Preparations; D011433:Propranolol