Flashcards in Coatzee's stuff Deck (32):
MAthematical description of drug movement throughout the body
Absorption, Distribution, Metabolism, Elimination
How the drug interacts with the target
Describe the drug concentration graph for an orally administered drug. IV adminstered drug.
The orally administered drug follows the normal curve of ADME.
IV injected drugs lack the absorption phase
Define AUC and what it indicates:
Area under the plasma concentration curve. Indicates the rate and extent of drug absorption.
It is a total concentration of drug in systemic circulation as a function of time
What drug is the AUC important for and why?
Fluroquinolones. Activity depends on AUC above MIC
Define Tmax and Cmax and what they indication
Tmax: Time taken to reach maximum plasma drug concentration. This is a rate of absorption indicator
Cmax: this is the max concentration reached in plasm. Extent of drug absorption indicator
Use Tmax and Cmax for IV, SQ, and IM injections True/False
FALSE; These are not applicable for IV injections
What is the activity of Beta-lactam drugs dependent on?
Time drug concentration is above MIC
What is the activity of aminoglycosides dependent on?
Cmax above MIC (Ideally more than 10x)
Describe the one compartment model.
Absorption is at one time point as it is administered via IV. The drug does not distribute in the other tissues. The clearance rate is expressed as Kel. Elimination is done via the kidney, liver, GIT.
Describe a zero order elimination:
This means that the drug is eliminated at a constant amount over a period of time.
Describe a first order elimination:
The drug is eliminated at a constant % over a period of time.
This is the amount of plasma cleared of a drug per unit time per unit bodyweight
Why is clearance rate important?
Excretion of drugs are affected by kidney failure. If you have 2x plasma creatinine concentration = aminoglycoside toxicity
This is elimination half time. It is the time that it takes for the concentration in the plasma to decrease by half.
What is half-life dependent on?
Speed of elimination process (Clp)
Exposure of drug to elimination
Doubling the dose does what?
Doubles the Cmax
Adds a half-life
Doubling the dose does not change what?
The half-life time
What's the difference in treating gram negative and gram positive bacteria?
Gram negative bacteria have the outer envelope; more important to make sure right dosage of drug is in the body
Describe a two compartment model:
This is when a drug can readily diffuse out of the central compartment. This is used to treat skin, eyes, prostate, etc. Biexponential IV curve has a bend in the curve.
Where does elimination occur in the two compartment model?
Still the central compartment only.
Describe the two phases in a two compartment model
Alpha phase: Fast; distribution of drug into peripheral tissues
Beta phase: Slow; elimination of drug from the central compartment
Describe Flip-Flop Kinetics
This is when absorption occurs slower than elimination; see in three compartment models
What portion of the three compartment model is of concern when it comes to residues?
Terminal gamma portion
What is the volume of distribution?
This is the amount of drug in the body divided by the plasma drug concentration
What is the clinical application of Vd?
The smaller the Vd, the less likely the drug is to distribute to other parts of the body
How do you calculate half time?
Volume of distribution divided by clearance rate
How is bioavailability calculated?
Compare the AUC of IM/SQ/Oral route against the AUC for IV administered drugs
What is the bioavailability of an IV drug?
What drugs are usually highly protein bound?
Ionized drugs: NSAIDs, Penicillin, and Sulfonamides