Chapter 4: Pharmacokinetics

Question 1

pharmacokinetics is derived from two Greek words:

Answer 1

pharmakon (drug or poison) and kinesis (motion).

Question 2

Pharmacokinetics

Answer 2

is the study of drug movement throughout the body.

Question 3

Pharmacokinetics also includes what

Answer 3

Pharmacokinetics also includes what happens to the drug as it makes this journey.

Question 4

There are four basic pharmacokinetic processes:

Answer 4

1. Absorption:
2. Distribution:
3. Metabolism:
4. Excretion:

Question 5

Absorption:

Answer 5

Absorption is the drug’s movement from its site of administration into the blood.

Question 6

Distribution:

Answer 6

Distribution is the drug’s movement from the blood to the interstitial space of tissues and from there into cells

Question 7

Metabolism:

Answer 7

Metabolism (biotransformation) is the enzymatically mediated alteration of drug structure.

Question 8

Excretion:

Answer 8

Excretion is the movement of drugs and their metabolites out of the body.

Question 9

Combo of metabolism + excretion=

Answer 9

elimination

Question 10

The four pharmacokinetic processes, acting in concert, determine:

Answer 10

The four pharmacokinetic processes, acting in concert, determine the concentration of a drug at its sites of action.

Question 11

Recall that the intensity of the response to a drug is directly related to:

Answer 11

Recall that the intensity of the response to a drug is directly related to the concentration of the drug at its site of action.

Question 12

To move throughout the body, drugs must

Answer 12

cross membranes.

Question 13

How do drugs enter the blood from their site of administration?

Answer 13

Drugs must cross membranes to enter the blood from their site of administration.

Question 14

Once in the blood, how does blood leave?

Answer 14

Once in the blood, drugs must cross membranes to leave the vascular system and reach their sites of action.

Question 15

Drugs must cross membranes to:

Answer 15

1. enter blood from their site of administration
2. drugs must cross membrane to leave vascular system and reach their sites of action
3. drugs must cross membranes to undergo metabolism and excretion

Question 16

The three most important ways by which drugs cross cell membranes are:

Answer 16

1. Passage through channels or pores,
2. Passage with the aid of a transport system, and
3. Direct penetration of the membrane itself.

Question 17

What is the most common way drugs cross membrane?

Answer 17

Of the three, direct penetration of the membrane is most common.

Question 18

Why do very few drugs cross membranes via channels or pores?

Answer 18

The channels in membranes are extremely small and are specific for certain molecules.

Consequently, only the smallest of compounds (e.g., potassium or sodium) can pass through these channels

Question 19

Transport Systems:

Answer 19

Transport systems are carriers that can move drugs from one side of the cell membrane to the other.

Question 20

What determines whether a transporter will carry a particular drug

Answer 20

Whether a transporter will carry a particular drug depends on the drug’s structure.

Question 21

P-Glycoprotein:PGP

Answer 21

PGP is a transmembrane protein that transports a wide variety of drugs out of cells.

Question 22

What sites are PGP present?

Answer 22

This transporter is present in cells at many sites, including the liver, kidney, placenta, intestine, and capillaries of the brain.

Question 23

What does PGP do in the liver?

Answer 23

In the liver, PGP transports drugs into the bile for elimination.

Question 24

What does PGP do in the kidneys?

Answer 24

In the kidney, it pumps drugs into the urine for excretion.

Question 25

What does PGP do in the brain capillaries?

Answer 25

In brain capillaries, it pumps drugs into the blood, thereby limiting drug access to the brain.

Question 26

What does PGP do in the placenta?

Answer 26

In the placenta, it transports drugs back into the maternal blood, thereby reducing fetal drug exposure.

Question 27

What does PGP do in intestines?

Answer 27

In the intestine, it transports drugs into the intestinal lumen and can thereby reduce drug absorption into the blood.

Question 28

For most drugs, movement throughout the body is dependent on the ability to penetrate membranes directly. Why?

Answer 28

(1) most drugs are too large to pass through channels or pores, and

(2) most drugs lack transport systems to help them cross all of the membranes that separate them from their sites of action, metabolism, and excretion.

Question 29

To directly penetrate membranes, drugs must

Answer 29

Membranes are composed primarily of lipids; therefore to directly penetrate membranes, a drug must be lipid soluble (lipophilic).

“like dissolves like”

Question 30

Certain kinds of molecules cannot penetrate membranes. They are:

Answer 30

-not lipid soluble and therefore cannot penetrate membranes.

-This group consists of polar molecules and ions.

Question 31

pH partitioning

Answer 31

The process whereby a drug accumulates on the side of a membrane where the pH most favors its ionization is referred to as ion trapping or pH partitioning.

Question 32

Absorption

Answer 32

is defined as the movement of a drug from its site of administration into the blood.

Question 33

What determines how soon effects will begin.

Answer 33

The rate of absorption determines how soon effects will begin.

Question 34

What helps determine how intense effects will be?

Answer 34

The amount of absorption helps determine how intense effects will be.

Question 35

Factors Affecting Drug Absorption:

Answer 35

1. Rate of Dissolution:
2. Surface Area
3. Blood Flow
4. Lipid Solubility
5. pH partitioning

Question 36

Drug Half-Life:

Answer 36

Drug half-life is defined as the time required for the amount of drug in the body to decrease by 50%.

Question 37

What does half life tell us:

Answer 37

half-life tells us that, no matter what the amount of drug in the body may be, half (50%) will leave during a specified period of time (the half-life).