Pharmacodynamics

Question 1

What is pharmacodynamics?

Answer 1

The effects of the drugs and their mechanisms of action within the body. (what the drug does to the animal)

Pharmacokinetics is what the animal does to the drug.

Question 2

What is a therapeutic effect?

Answer 2

The effect that we want the drug to have.

Question 3

What is a side effect?

Answer 3

Expected effects secondary to the intended effect (can be good or bad) .

Question 4

What is an adverse effect?

Answer 4

Unintended and unwanted effects (including the desired effect NOT being produced).

Question 5

What is a toxic effect?

Answer 5

Responses to a drug that are harmful to the health or life of the animal.

Question 6

What are osmotic diuretics?

Answer 6

Example of physical drug interactions.

These drugs drag water with them through the body by osmosis until they are excreted.

Question 7

What are antacids?

Answer 7

Example of physical drug interactions.

Drugs that interact with the acid in the GI system.

Question 8

What is radioactive iodine?

Answer 8

Example of physical drug interactions.

Iodine concentrated in the thyroid will be focally destroyed by the radiation.

Question 9

What are Ionotropic receptors?

Answer 9

Ligand-mediated receptors in the membrane creating a channel or pore to allow an influx of ions.

Drugs can activate them or prevent opening.

Example: Neurotransmitters

Question 10

What are Metabotropic receptors?

Answer 10

G-protein coupled receptor where a drug binds and causes G proteins in the cell to take up GTP and open a channel.

Example: Secretory/smooth muscle functions (muscarinic ACh receptors)

Question 11

What are Kinase-coupled receptors?

Answer 11

Transmembrane proteins where the intracellular portion has enzymatic activity (kinase domain) which are activated by phosphorylation.

Example:
Insulin receptors

Question 12

What are nuclear receptors/transcription factor receptors?

Answer 12

Receptors are in the cytoplasm but translocate to the nucleus and alter transcription when bound to a ligand.

Example: Steroid/Thyroid hormones.

Question 13

What are receptor subtypes?

Answer 13

When receptors have different effects from the same signaling molecule.

Example: Adrenergic receptors have alpha and beta subtypes.

Question 14

What is up-regulation?

Answer 14

Increase in the number of receptors resulting in an increase in the effect of the drug.

Question 15

What is down-regulation?

Answer 15

Reduction in the number and effect of the receptors by internalizing in lysosomes, recycling, degrading, or developing tolerance.

Question 16

What is tachyphylaxis?

Answer 16

An acute tolerance to a drug.

Question 17

Drugs effect on voltage-gated ion channels?

Answer 17

Blocking of ion channels can occur by physically obstructing the channel or modulating its opening/closing.

Question 18

What are prodrugs?

Answer 18

Drug needs to be metabolized before it is in its active form.

Question 19

What are carrier proteins?

Answer 19

Carry small, polar molecules through the membrane (in or out) and this movement can be prevented by drugs.

Question 20

What is an agonist?

Answer 20

Mimic the effect of the endogenous ligand.

Question 21

What is a full agonist?

Answer 21

Binds to the receptor to elicit a maximal response.

Question 22

What is a partial agonist?

Answer 22

Binds to the receptor but does not cause as much of an effect translating to a lower efficacy.

Also called a ceiling effect.

Question 23

What is a reverse agonist?

Answer 23

Binds to the receptor and cause the opposite effect of the endogenous ligand.

Question 24

What is an antagonist?

Answer 24

Binds to the receptor but does nothing except prevent anything else from binding (blocks the receptor).

Question 25

What is competitive antagonism?

Answer 25

Antagonist and agonist compete for binding resulting in a varying degree of efficacy depending on which has the greater concentration.

Question 26

What is irreversible competitive antagonism?

Answer 26

Receptors are never free and the competing ligand does not have a chance once the antagonist is introduced.

Question 27

What is non-competitive antagonism?

Answer 27

Interacts somewhere other than the receptor to block the ability of the normal ligand to bind to the receptor

Question 28

What is a mixed agonist-antagonist?

Answer 28

Acts as an agonist on one receptor but an antagonist on the other receptor.

Question 29

What is chemical antagonism?

Answer 29

Two drugs chemically inactivate each other.

i.e. ppt forming in the fluid line.

Question 30

What is pharmacokinetic antagonism?

Answer 30

One drug alters the ADME of the other drug and reduces its effect.

Question 31

What is physiologic antagonism?

Answer 31

Drugs have opposite effect that cancel each other out.

i.e. increase BP meds, decrease BP meds.

Question 32

What is efficacy?

Answer 32

The maximal effect a drug can have (e=1 is the full effect)

A partial agonist may never be able to achieve e=1 (ceiling effect)

Question 33

What is potency?

Answer 33

Comparison of the concentration of two drugs necessary to induce the same magnitude of effect.

**A partial agonist could be more potent

Question 34

What is EC50? (Effective concentration 50%)

Answer 34

Concentration at which the drug produces 50% of its maximal effect. (only applies to in vitro studies)

Question 35

What is ED50? (Effective dose 50%)

Answer 35

Dose that produces a result in 50% of the animals (this applies to in vivo observed effects)

**LD50 is the dose at which 50% of animals are killed

Question 36

What is the therapeutic index?

Answer 36

The ratio of LD50 to ED50.

The higher the therapeutic index (curves will be far apart) the safer the drug.

Question 37

What is the ‘onset of action’?

Answer 37

The time required after drug administration for a response to be observed (aka latent period)

Question 38

What is the ‘duration of action’?

Answer 38

The length of time that a drug is effective (onset to termination of action)

Question 39

Clicker question:
Compared to a full agonist, a partial agonist can generally be assumed to have which of the following:

A. lower efficacy compared to a full agonist
B. lower potency compared to a full agonist
C. an ability to act as an inverse agonist
D. a tendency to cause receptor down-regulation

Answer 39

A. lower efficacy compared to a full agonist

Has a ceiling effect, so will not reach the same level of efficacy.

BUT potency is not necessarily dictated by partial or full agonist.