Module 6 Flashcards
What is the underlying principle of clinical pharmacokinetics?
A relationship exists between the effects of a drug and the concentration of drug in the body.
What are the most important parameters determining drug disposition in humans?
Clearance, volume of distribution, elimination half-life, bioavailability
Ideally, drug concentrations would be measured from _______, however this is not feasible (generally, and thus drug concentrations are usually measured in ________.
the site of action
plasma
Why is the plasma a good site to measure drug concentrations?
1 - Relatively non-invasive
2 - Good correlation between plasma concentration and therapeutic/toxic effects (generally)
How is plasma obtained?
Phlebotomy (take blood from pt) –> centrifuge blood sample –> obtain plasma
What is measure in terms of drug concentration, in plasma.
Total drug concentration (since free drug concentration is difficult)
Describe the oral administration plasma concentration vs. time curve.
A >> E Cmax - A = E A << E A - absorption E - elimination
What are the different characteristics of plasma concentration time curves?
MEC - minimum effective concentration
Duration
Toxic concentration
Therapeutic range
The minimum concentration required to have a therapeutic effect.
MEC - minimum effective concentration
Length of time the drug is above the MEC.
Duration
Above which, toxic side effects will occur.
Toxic concentration
Range at which the plasma drug concentration is between the toxic concentration and the MEC.
Therapeutic range
The ________ of the therapeutic range is an index for how ________ a drug can be used.
width
safely
Drugs with a narrow therapeutic range often undergo ________ _________ to ensure that drug concentrations are within the target range.
Therapeutic monitoring
Describe therapeutic monitoring.
Typically performed on troughed blood samples
= Take a blood sample just prior to patient’s next dose
What is another word for therapeutic range?
Therapeutic window
Why do oral drugs have a lag time before they reach the MEC?
They have to be absorbed first, and rise in plasma concentration to have therapeutic effects
Using IV administration, there is no drug ________.
absorption
Describe the different phases of the IV plasma drug concentration time curve.
I >> E Steady state - I = E I << E = infusion stopped I - infusion rate E - elimination rate
The elimination of a drug given by IV bolus follows what type of kinetics?
First order - the rate of elimination is dependent on the blood concentration
When patients take repeated dosing of drugs, ___________ occurs.
accumulation
Repeated dosing of drugs results in ________ in the body until a ________ is reached. This is called the _______ _______.
accumulation
plateau
steady state
When drugs are repeatedly administered orally or as an IV bolus, drug concentrations fluctuate. The high level is called the ______, and the low level is called the _________. The goal of drug therapy is for the fluctuations at steady state to be within the ________ _______.
peak
trough
therapeutic range
Steady state is reached in repeated dosing when?
When the peak and trough concentrations are the same between doses.
