Unit 1- Pharmacokinetics Flashcards
Clearance
Volume of plasma containing total amount of drug removed in unit time mL/min or L/h
Use of clearance
To assess excretory capacity of an organ
Renal Clearance
Volume of plasma containing the amount of drug that is removed by the kidneys in unit time
Total Body Clearance
Sum of clearance rates for each mechanism involved in eliminating the drug
Rate of Drug Elimination
Amount of drug being eliminated per unit time, clearance is the proportionality factor to determine rate of elimination
Overall Clearance Estimation
Estimated by measuring plasma concentrations at intervals following a single IV bolus
Constant-Rate IV infusion
Used to determine drug clearance by measuring the plasma concentration at intervals, helps to calculate dose rate needed to achieve steady-state plasma concentration
Constant IV Time curve
Plasma concentration increases from 0 but reaches a steady state plateau, and then drops off when infusion stops
IV bolus Time Curve
Plasma concentration rises abruptly and then drops to 0
Elimination Half-Life
Time necessary for plasma concentration to drop by 50%
Increase in Distribution and half life
Increase in volume of distribution leads to more drug being sequestered in the tissues, and half life will increase
Organs that sequester drugs
Fat and bones
Increasing half life
Decreased renal or hepatic blood flow, decreased renal function, decreased metabolism
Decreasing half life
Increased hepatic blood flow, decreased protein binding, increased metabolism
First Order Elimination
Same volume of drug will be cleared by an organ regardless of plasma drug concentration, half life remains constant
Zero Order Elimination
Occurs when mechanisms for first order elimination become saturated, rate of elimination is constant regardless of plasma drug concentration, half life varies
Importance of Pharmacokinetics
interpret drug concentration, adjust dose regimens, identify drug interactions, individualize dose regimen
Therapeutic Drug Montoring
To achieve desired therapeutic effect while minimizing adverse affects in each individual patient
Pharmacokinetic Modeling
Used to predict behavior of a drug in the body, drug is given in a single dose, samples are collected over time
Single Compartment Model
Body is considered one compartment, drug moves out of the body at a single rate
Use of One Compartment Model
When plasma concentration falls exponentially after administration
Two Compartment Model
Two compartments for the tissue and plasma, drug molecules can leave and enter the peripheral compartment via the central compartment by distribution constant and redistribution constant
Multicompartment Model
Employed when experiments are conducted over long time frames, ie describing tissue residue of a drug in a food producing animal
