Pharmacodynamics

Question 1

A clinician wants to calculate the therapeutic index of a drug, but only has information from a graded dose-response curve. Is this possible?

Answer 1

No, a quantal dose-response curve is needed to determine TI

Question 2

A patient is prescribed two drugs. The effect of taking the two drugs together than each drug individually is much greater. What term describes this relationship?

Answer 2

Synergistic

Question 3

What term describes a drug response that is not often observed?

Answer 3

Idiosyncratic

Question 4

What is Kd?

Answer 4

Kd is the dose of a drug necessary for half of the receptors to be bound

Question 5

What term describes a decreased response to a drug compared to most individuals?

Answer 5

Hyporeactive

Question 6

True/False. An antagonist has no physiological effect.

Answer 6

True. An antagonist binds the receptor and prevents the agonist from binding, but has no physiologic effect itself.

Question 7

The heart achieves a maximum effect to catecholamines when only 10% of its receptors are bound. The remaining 90% are termed what kind of receptors?

Answer 7

Spare receptors - that is, extra receptors that need not be bound in order to achieve maximal effect

Question 8

A drug has a high Kd value. What does this indicate about the drug’s affinity for the receptor?

Answer 8

Kd and affinity are inversely related. A high Kd indicates low affinity for the receptor.

Question 9

What is an antagonistic drug relationship?

Answer 9

The combined effect of two drugs is less than the sum of the effect of each individual drug

Question 10

What is a chemical antagonist?

Answer 10

An antagonist that does not bind a receptor. It makes some drug/protein unavailable via ionic binding

Question 11

What is drug potency?

Answer 11

The amount of drug necessary in order to produce a given effect

Question 12

True/False. A partial agonist may out-compete a full agonist.

Answer 12

True. In this case, the effect will be diminished.

Question 13

These types of bonds are responsible for drug-receptor interactions.

Answer 13

Weak ionic bonds

Question 14

This type of agonist produces a lower response at full receptor occupancy.

Answer 14

Partial agonist - formation of active and inhibitory complexes

Question 15

What term describes a drug relationship in which neither drug influences the effect of the other?

Answer 15

Additive/Summation

Question 16

A competitive antagonist causes an increased in EC50, but maintains Emax. What is the effect of a non-competitive antagonists on EC50 and Emax?

Answer 16

Emax will decrease, but EC50 will remain the same assuming no spare receptors are present

Question 17

What formula is used to calculate therapeutic index?

Answer 17

TI = TD50/ED50

Question 18

What is the difference between receptor downregulation and tolerance?

Answer 18

Downregulation causes a decrease in the overall number of receptors due to prolonged exposure to an agonist. Tolerance is a gradual loss of response to the agonist after repeated exposure.

Question 19

This type of receptor regulation leads to increased sensitivity to an agonist.

Answer 19

Receptor upregulation

Question 20

What is the difference between hyperreactive and hypersensitivity in drug responsiveness?

Answer 20

Hyperreactivity is an increased drug response. Hypersensitivity refers to an immunologic or allergic reaction to a drug.

Question 21

What is Emax?

Answer 21

Emax is the greatest effect an agonist can produce at the the highest tolerable dose

Question 22

How do inverse agonists differ from antagonists?

Answer 22

Antagonists have no effect. Inverse agonists form inhibitory complexes that produce an effect below constitutive activity.

Question 23

What are the four primary roles of receptors?

Answer 23

Detect signals, determine dose-response, mediate actions of drugs, responsible for selectivity

Question 24

True/False. Partial and inverse agonists behave as competitive antagonists in the presence of a full agonist.

Answer 24

True

Question 25

These types of bonds are extremely strong and considered unbreakable.

Answer 25

Convalent bonds

Question 26

What information can be calculated using information from a quantal dose-response curve?

Answer 26

ED50 (dose at which 50% patients exhibit quantal effect), TD50 (toxic dose), LD50 (lethal dose), TI (therapeutic index)

Question 27

What is a functional/physiological antagonist?

Answer 27

An antagonist that binds to a different receptor in order to exert a response opposite that of the agonist (ex: glucocorticoids increase blood glucose, but insulin decreases blood glucose)

Question 28

Drug A has an EC50 of 5mg. Drug B has an EC50 of 12mg. Which drug is more potent?

Answer 28

Drug A - lower dose is necessary in order to produce an effect

Question 29

What receptor state is favored under normal conditions?

Answer 29

Inactive receptor state. A continuous equilibrium always exists between active and inactive receptor, but inactive is favored in the absence of an agonist.

Question 30

A graph shows a dose-response and drug binding curves. The dose-response curve has a lower Kd than the drug binding curve. What does this indicate?

Answer 30

The presence of spare receptors - the maximum effect of the drug is being achieved before all receptors are bound

Question 31

What protein is involved in the destruction of receptors by lysosomes?

Answer 31

Beta-arrestin

Question 32

An antagonist binds to a receptor. The agonist dose is increased, but no change in effect is observed. What type of antagonist is bound to the receptors?

Answer 32

Non-competitive antagonist - irreversible and cannot be overcome

Question 33

True/False. Receptors may be immediately desensitized following activation.

Answer 33

True. This prevents harmful continuous activation. The desensitization is only temporarily and may last milliseconds.

Question 34

What type of agonist produces maximal effects?

Answer 34

Full agonist

Question 35

What is the relationship between Emax and efficacy?

Answer 35

Higher Emax = better clinical efficacy

Question 36

A researcher wants to compare the Emax of three drugs using a dose-response curve. What type of curve is needed?

Answer 36

Graded dose-response curve

Question 37

What is tachyphylaxis?

Answer 37

A form of desensitization that occurs very rapidly

Question 38

What is the therapeutic window?

Answer 38

Dosage range between minimum effective dose and minimum toxic dose