Pharmacokinetics Flashcards
The protein-binding of a drug
A. Will render the drug inactive
B. Will enable the drug to cross membranes
C. Enables the drug to undergo metabolism and excretion
D. Is subject to competition and would be clinically important across any degree of protein-binding
E. AOTA
A
For at least 99% of the drug to be removed from the body after a single dosing under the first-order kinetic reaction, this minimum number of half-lives should have been completed
A. 3 B. 5 C. 7 D. 9 E. 12
C
Pharmacokinetic parameters in distribution is/are:
A. Bioavailability and half-life B. Protein binding and apparent volume of distribution C. Half-life and clearance D. A and B E. B and C
B
Oral bioavailability is dependent on liver and renal metabolism. T/F
F
Bioavailability is a measure of drug absorption, may be affected by first pass metabolism but not by renal metabolism/clearance
Noncompartmental analysis is appropriate only for 1-compartment model. T/F
F
Non-compartmental analysis holds no assumptions in the compartmentalization of drug distribution
The intravenous route is considered 100% absorption. T/F
T
Since all of the drug administered enters the systemic circulation
Oral and IV AUC are adequate to compute for oral bioavailability provided that the doses are the same. T/F
T
The most important of the CYP450 enzymes is CYP3A4 because it metabolizes 33% of all drugs that are metabolized. T/F
F
It metabolizes over 50% of the prescription drugs metabolized by the liver.
For a drug that behaves in a linear fashion, doubling the dose would mean doubling the Cmax and AUC. T/F
T
In first order reactions, rates are linearly related to dose administered.
If the Ka is increased, absorption is faster and Cmax will be attained earlier. T/F
T
An increase in Ka (rate of absorption), will lead to a lower Tmax—hence faster absorption and Cmax reached earlier
In a one-compartment model with first order input and first order elimination, absorption stops when Cmax is reached. T/F
F
Once Cmax is reached, absorption does not stop, it’s just that Ke>Ka rate of elimination is faster than absorption, hence the graph starts to go down
For a first-order, two compartment equation, distribution is immediate and instantaneous within the same compartment. T/F
F
In a 2-compartment model, the distribution phase from the central to the peripheral compartment is signified by the steeper initial slope of the graph, hence it’s not immediate.
If there is a change in plasma protein binding, the impact will be greater in a drug that is more highly protein-bound than one which is less protein-bound. T/F
T
Scenario where there is 1% decrease in protein binding: 99% protein bound- from 1% free drug becomes 2% which is a 100% increase 90% protein bound- from 10% free drug becomes 11% which is a 10% increase
Absolute bioavailability always varies from 0 to 1. T/F
T
It’s a ratio between BA in oral and IV administration.
Vd should always match actual body fluid compartments. T/F
F
Volume of distribution is a hypothetical volume, hence it can be larger than actual body fluid volumes.
The therapeutic margin ranges from the minimum therapeutic concentration to the maximum therapeutic concentration. T/F
F
Aka therapeutic index: ratio of the minimum toxic dose, and the minimum effective dose
Increasing dosage will always increase therapeutic effect. T/F
F
When ceiling dose is reached, increased dose will not result to increased response (hyperbolic graded dose-response curve)
Regardless of the number of compartments, when the equilibrium is reached, the whole system behaves like a one compartment model. T/F
T
When the drug distribution to all compartments reaches equilibrium, it acts like a one compartment model
The purpose of metabolism is to convert the drug into a more polar form and make them more excretable by the kidneys. T/F
T
A drug that is highly protein-bound would have a high volume of distribution. T/F
T
A highly protein bound drug stays intravascularly, hence Vd will be limited to the intravascular blood volume.
After giving a drug repeatedly for 8 half-lives, we are confident that it is in steady state concentration
T
Steady state is achieved after 4-7 half lives
The half-life of a drug is 8 hours. What is the plasma drug concentration after 24 hours if the current concentration is 100 pmol/L?
A. 25 pmol/L B. 16.33 pmol/L C. 12.5 pmol/L D. 6.25 pmol/L E. 3.125 pmol/L
C
In 24 hours= 3 half lives.
After 1st 8 hours= 50 pmol/L
After 2nd 8 hours= 25 pmol/L
After 3rd 8 hours= 12.5 pmol/L
If clearance is reduced by 50% and volume of distribution is doubled, half-life is equivalent to
A. Reduced by 75%
B. Increased by 1.33x
C. Increased by 4x
D. No change
C
t ½ = 0.693Vd/ Cl
t ½ = 0.693 (2) Vd/ 0.5Cl
t ½ = 4(0.693Vd/ Cl)
What happens to bioavailability as the dose increases when there is saturable liver metabolism?
A. Increase
B. Decrease
C. Remains the same
A
When first pass metabolism has been saturated, the additional dose will not undergo first-pass anymore, hence BA increases