Drug Receptors & Pharmacodynamics

Question 1

What determines drug dose?

Answer 1

affinity to receptor

• many drugs given in mg amounts and measure in ng/dL concentrations
• mus thave high affinity

Question 2

Drug size, shape, charge are impt for what characteristic of receptors?

Answer 2

selectivity

Question 3

what mediates pharmacologic action of drugs?

Answer 3

receptors

-implies “signal transduction”

Question 4

Dose Response curves

Answer 4

Question 5

Dose-response curve as semi-log plots

Answer 5

y-axis= agonist effect

x-axis= log (drug concentration)

-yields sigmoidal curve

Question 6

Comparing dose-response curve. Which drug is more portent?

Answer 6

Drug X is more potent than Drug Y

• lower drug concentration for EC50
• but equally efficious (max. effect same)

Question 7

Compare dose-response curves. Which is more efficacious?

Answer 7

Drug X is more efficacious than Drug Y

• ..and more potent too; EC50 is lower

Question 8

What does competitive antagonist do to the dose response curve?

Answer 8

Competitive antagonist shift curve right

• EC50 also increases
• maximal effect remains the same

Question 9

How does competitive antagonism do to the max effect (at high dose)? EC50?

Answer 9

• The max effect (at high does) remains unchanged
• Increased EC50

Question 10

How does a NON-competitive antagonist do to max effect? EC50?

Answer 10

• Max effect is lower
• EC50 is unchanged

Question 11

What does a non competitivea antogonist do to the hight of sigmoidal curve on semi-log and non-log

Answer 11

lower maximal height

Question 12

Chemical antagosnism

Answer 12

Binds to agonist preventing action at receptor

e.g. Protamine vs Heparin

Question 13

Physiologic antogonism

Answer 13

activate a different pathway with essentially opposite effects

e.g. isulin vs glucocorticoid-induced hyperglycemia

Question 14

Potency of dose response curves

Answer 14

• x-axis issue
• what concentration of drug yields 50% maximal effect? EC50

Question 15

Efficacy Dose-response curve

Answer 15

• y axis issue
• What is the maximal response?

Question 16

When is Quantal Dose-effect curves used?

Answer 16

when the effect is either/or?

• provide infor about the variation in sensitivity to the drug in a given population.
• response to at progressively increasing doses
• small variation=steep curve
  e. g. seizure, relief of headache, death

Question 17

Media Effective dose/ Media toxic (lethal dose)/ therapeutic index

Answer 17

used in quantal dose effective curves

1. ED50
2. TD50, LD50
3. ratio btw LD50 to ED50: lower index can overdose more easily

Question 18

Variations in drug response: Idiosyncratic

Answer 18

usually due to genetic diff

Question 19

Variations in drug response: respose

Answer 19

degree of response varies with therapy

• tolerance
• tachyphylaxis (repsonse dimishes rapidly after administrations, may be related to depletion of neurotransmitters)