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32 Cards in this Set

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Anatomical and physiological factors involved in the model of absorption from extravascular sites includes what?
Includes factors such as GI motility, and surface area for absorption.
Give an example of how the dosage form used can effect absorption?
For example, a solid needs to first disintegrate, then dissolve in GI fluids before absorption is possible.
Give some examples of the physicochemical properties of a drug?
Lipid solubility, size, etc.
For oral absorption the rate of drug build-up in the body is equivalent to what?
It is the rate of drug absorption minus the rate of drug elimination.

dDb/dt = dDgi/dt - dDe/dt
What does Dgi equal?
Dgi is the amount of drug in the gastrointestinal tract.
What does De equal?
The amount of drug eliminated.
What three phases can be identified from the PLASMA DRUG LEVEL-TIME curve?
1. The absorption phase

2. post-absorption phase

3. elimination phase
In a plasma drug concentration verses time curve what is equal at the peak concentration?
At peak concentration:

Rate of absorption = rate of elimination

[dDgi/dt] = [dDe/dt]
In a Cp against t curve for oral absorption what is the relationship between the rate of absorption and rate of elimination during the post-absorption phase?
During the post-absorption phase the rate of absorption is less than the rate of elimination.
During the absorption phase what is the relationship between the rate of absorption verses the rate of elimination?
During the absorption phase the rate of absorption is greater than the rate of elimination.
During the elimination phase what is the rate of absorption equal to?
During the elimination phase the rate of absorption is 0.
What is Ka?
Ka is the first-order rate constant for absorption.
What do K and Ka make it possible to determine?
They make it possible to determine peak and trough plasma concentrations during multiple dosing.
If Ka increases at a steady K how does it affect the Cmax, tmax, and AUC?
1. Cmax increases

2. tmax decreases

3. AUC remains the same
If k increases at a steady Ka how does it affect the Cmax, tmax, and AUC?
Cmax, tmax, and AUC all decrease
The parameters Ka, K, and tmax are useful in determining what?
They are useful in determining the bioequivalence of chemically equivalent products.
The selection of a ? and ? is typically based on the data gathered.
The selection of a model and order is typically based on the data gathered.
When does a Zero-order absorption process occur?
It occurs when the process is saturable or when a controlled-release system is used.
The Wagner-Nelson Method assumes a ? model.
The wagner-nelson method assumes a one-compartment model.
What is Du representative of in the Wagner-Nelson Method?
Du is the amount of unchanged drug in the urine.
In Wagner-Nelson Method why is only the initial segment of the curve used?
Because the terminal part tends to be non-linear (as absorption nears 100%, it becomes difficult to accurately assay Cp)
Only ? ? samples will yield accurate pharmacokinetic parameters.
Only valid urine samples will yield accurate pharmacokinetic parameters.
What does De represent?
De is the total amount of drug eliminated (parent and metabolites).
In a one-compt model what does Db equal?
Db = VdCp
The loo-riegelman method assumes what? What is required to determine all the parameters needed?
It assumes a two-compt model. The drug needs to be given both po and iv in order to determine all the parameters needed.
In the loo-riegelman method what does Dp, Dt, and Du refer to respectively?
1. Dp = amt of drug in the central compt

2. Dt = amt of drug in the tissue compt.

3. Du = amt of drug eliminated by all routes
When using the feathering technique does k or ka represent the steeper slope?
ka represents the steeper slope.
When can a reversal of the values for the rate constants ka and k occur?
A reversal of the values for these can occur when they are estimated from oral absorption data. This occurs for drugs with very fast elimination (k>ka).

Reversal occurs for some drugs with k>.69/hr such as isoproterenol and salicyluric acid.

It could also occur for an extended release product if ka drops well below k.
In order to be sure that Ka>K (as would be indicated by oral data) the drug must be given to the same patient how?
In order to be sure that Ka > k the drug must be given to the same patient intravenously.
A drug with a high value for k, which means it has a ? half-life, is probably not suitable for what?
A drug with a high value for k, which means it has a short half-life is probably not suitable for oral administration.
What may create a lag time in some individuals?
Factors such as stomach emptying time and intestinal motility create a lag time in some individuals. This is a delay in absorption.
Absorption begins at the end of ?. What does onset time represent?
Absorption begins at the end of lag time (t0). Onset time, on the other hand, represents the time needed for drug levels to attain the minimum effective concentration.