27-09-2013, 04:53 PM
One compartment open model
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Models and compartments
Model: is a mathematic description of a biologic system and is used to express quantitative relations concisely
Compartment: is a group of tissues with similar blood flow and drug affinity. A compartment is not a real physiologic or anatomic region.
Drug distribution: drug distribute rapidly to tissues with high blood flow and more slowly to tissues with low blood flow.
Drugs rapidly cross capillary membranes into tissues because of passive diffusion and hydrostatic pressure
INTRODUCTION
when a drug is given extravascularly the drug moves in the human body through the process of absorption, distribution, metabolism and elimination.
After sometime, the drug is completely eliminated from our body
The body is open with respect to the drug movement.
The movement of the drug in the body can be described with the help of a mathematical model.
One compartment open model is the simplest model which can depicts the body as a single homogeneous unit.
One compartment open model
The process of drug absorption from the absorption site may be in first order kinetics
Once the drugs enter in to the systemic circulation it rapidly distribute to other body fluids and tissues and a dynamic equilibrium is achieved instantaneously between the drug inn the blood and the drug in other tissues.
Any changes that occur in the plasma level of a drug reflect proportional changes in the tissue drug level
Estimation of pharmacokinetic parameters-IV Bolus administration
A drug that follows one-compartment kinetics and administered as rapid i.v injections, the decline of plasma drug concentration is only due to elimination of drug from the body (elimination phase).
Elimination phase can be characterized as 3 parameters
1. Elimination rate constant
2. Elimination Half –life
3. Clearance