Pharmacokinetics

Question 1

Pharmacokinetics

Answer 1

Use of mathematical models to quantitate the time course of drug disposition in man and animals

Allows us to evaluate the rate and extent of ADME

Question 2

Rate

Answer 2

Refers to how fast the mass (dose) of a drug changes per unit time (mg/min)

Question 3

Extent

Answer 3

How much the mass (dose) of a drug changes in total

Question 4

Metabolism + Excretion = ?

Answer 4

Elimination

Question 5

Remember, she said she would give us the formulas. We just need to know how to apply them.

Answer 5

:) isn’t that just dandy

Question 6

Area under the curve (AUC)

Answer 6

measure of drug exposure

Question 7

Bioavailabillity (F)

Answer 7

Fraction of the given dose which finds its way into systemic circulation

** Calculated from the AUC

Question 8

What are some pharmacokinetic models?

Answer 8

• Compartment model
• Non-compartmental model (stochastic)
• Population pharmacokinetics
• Allmetric scaling
• Non-linar models

Question 9

What model views the patient as a number of compartments?

Answer 9

Compartment model

Question 10

What are the three types of compartment models?

Answer 10

One-compartment model
Two compartment model
Multi-compartment model

Question 11

What model involves using statistical analysis of large numbers of actual animal data and is the PRIMARY method by which pharmacokinetic parameters are now determined in veterinary medicine?

Answer 11

Non-compartmental (stochastic)

Question 12

What model estimates pharmacokinetics by looking at populations?

Answer 12

Population pharmacokinetics

Question 13

What model uses pharmacokinetic data in multiple species to try to predict the behavior of a drug in a species for which this information is unknown?

Answer 13

Allometric scaling

Question 14

What mode is used when drugs follow zero-order kinetics?

Answer 14

Non-linear models

Question 15

What three things are important for an optimum dosage regimen?

Answer 15

Effective
No toxicity
No drug residues

Question 16

Bioequivalence

Answer 16

Different formulations of the same drug are bioequivalent when they are absorbed to a similar extent and similar rate

Question 17

Half- Life (t1/2)

Answer 17

The time required for the drug concentration to decrease by one-half (50%).

• Will be constant with first-order elimination (does not depend on dose)

Question 18

Zero- Order Elimination

Answer 18

The amount of drug eliminated per unit time is fixed, regardless of plasma concentration

Question 19

First- Order Elimination

Answer 19

The proportion of drug eliminated per unit time is fixed and the rate of elimination is dependent upon plasma concentration

The rate will change over time, but will do so in predictable way

Question 20

What are some examples of drugs that use zero-order elimination?

Answer 20

• Phenylbutazone in horses
• Acetaminophen in cats
• Phenytoin in dogs

Question 21

When saturation occurs, the clearance _____ (increase/decrease) and the half- life ________ (increase/decrease) which can lead to drug accumulation and potential toxicity.

Answer 21

clearance decreases

half-life increases

Question 22

After 1 half-life ___ (%) of the drug is gone. 2 half-lives? 3.3 half-lives? 5 half-lives?

Answer 22

1 half-life = 50% of the drug gone
2 half-lives = 75%
3.3 half-lives = 90%
5 half-lives = 97%

Question 23

Apparent volume of distribution (Vd)

Answer 23

The theoretical volume a drug would occupy if it was evenly distributed through the body at the same concentration as in plasma

Question 24

What does it mean to have a very high Vd?

Answer 24

It suggests that the drug is being sequestered in tissue and distributes preferable to tissues.

Question 25

What does it mean to have a very low Vd?

Answer 25

It suggests that the drug is not being distributed to all of the tissues.

Question 26

Total body clearance

Answer 26

The volume of distribution of drug in the body cleared of the body per unit time

sum of the clearance by the kidneys, liver, and everywhere else

Question 27

As clearance increases, t1/2 ____ (increase/decrease)

Answer 27

Decreases

Question 28

As Vd increases, t1/2 ______ (increase/decrease)

Answer 28

Increases

Question 29

Plasma concentration at steady state (Cp)

Answer 29

Concentration at which the amount of drug going in is equal to the amount going out.

Question 30

After how many half-lives of repeated dosing or CRI will the plasma concentration be 97% of the eventual steady state concentration?

Answer 30

5 half-lives

Question 31

T/F: The time to achieve steady state levels depends on the dose given.

Answer 31

F: the time to achieve the steady is INDEPENDENT of dose

Question 32

The higher the dose, the ______ (higher/lower) the Cp

Answer 32

Higher

Question 33

Watch for units in your calculations!!!!!

Answer 33

Don’t make stupid mistakes….