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level: Level 5 - MODELS

Questions and Answers List

level questions: Level 5 - MODELS

Question	Answer
It is a hypothesis using mathematical terms to describe quantitative relationships concisely	Models
Why use Pharmacokinetic models?	1 To stimulate the RATE PROCESS of drug ADME to predict drug concentration in the body 2 Predict plasma, tissue, and urine drug level with any dosage regimen 3 Calculate the optimum dosage regimen for each patient individually 4 Estimate the possible accumulation of drugs and metabolites 5 Correlate drug concentration with pharmacologic or toxicologic activity 6 Evaluate differences in the rate or extent of availability between formulations (bioequivalence) 7 describe how changes in physiology or disease affect the absorption, distribution or elimination of the drug 8 explain drug interaction
Types of Pharmacologic Models	1 Empirical Models 2 Physiologically based models 3 Compartment models
A model which is EXPERIENCE-BASED practical but not useful	Empirical model
A model which is used for concentrations of drug in the LIVER but have limitations	Physiologically-based models
A model which is used as representation; simple and useful	Compartment models
Compartment models TYPES	1 Caternary models 2 Mamillary models 3 Physiologic Pk models
Train Model Compartments joined to one another in a series like compartments of a train It is not used because it is not observed that anatomically or physiologically various organs are directly linked to the blood compartment	Caternary models
Most commonly used model used in Pharmacokinetics. Consist of one or more compartments connected to a Central compartment Central compartment (Represent the plasma and highly perfused tissues)	Mamillary models
Blood flow or Perfusion Model Binding of drug in the tissues determined the uptake Realistic prediction but requires much information to describe the pk models, hence difficult to obtain Determination of drug concentration is hard to achieve due to different kinetics to the flow	Physiologic Pharmacokinetic Model
Is a tank containing a volume of fluid that rapidly equilibrate with the drug Assumes a drug is given by IV injection and dissolves rapidly into the body fluids A fraction of the drug would be continually eliminated as a function of time	One-Compartment Model
Drug can move between the central/plasma compartment to ad from the tissue compartment. Drug in central compartment + Drug in tissue compartment = Total Amount of Drug	Two-Compartment Model
Represents the plasma and tissues in the body that easily equilibrate with the drug concentration These tissues are kidneys and liver Amount of drugs in the body and amount eliminated can be estimated using these compartment models	Compartment
Are used to REPRESENT the overall rate processes of drug entry into and exit from the compartment	Rate constants
Rate constants TWO PARAMETERS	1 Fluid Volume that will dilute the drug (v) 2 Elimination rate of drug (k) per unit of time
Represents the pharmacokinetic Rate Constants	K
At what time should plasma drug concentration be taken in order to best predict drug response and side effects?	At time of elimination