L57- Pharmadynamics

Question 1

What is efficacy?

Answer 1

describes the ability of the drug, after binding to the receptor, to activate transduction mechanisms that lead to a response”

Question 2

what is intrinsic efficacy?

Answer 2

describes the ability of the drug, after binding to the receptor, to activate transduction mechanisms that lead to a response in a tissue

Question 3

why are tissues different from each other?

Answer 3

◦ different number of receptors present
◦ different nature of coupling of receptors to response
◦ different drugs (different interaction with different parts of tissue?)

Question 4

what is an agonist?

Answer 4

a drug has affinity, high efficacy and rapid rate of association and dissociation with its receptor

Question 5

what is a partial agonist?

Answer 5

• a drug has affinity, weak efficacy and moderate association and dissociation. It produces an effect < the full agonist when it has saturated the receptors. It acts as antagonist in the presence of full agonist.
• it can look like a full agonist

Question 6

what is a antagonist?

Answer 6

• drug that prevents the action of an agonist.
• Antagonist has affinity for a receptor, but does not produce a conformational change in the receptor protein
• little of no efficacy
• has affinity

Question 7

what is an inverse agonist?

Answer 7

it turns of the small activation a receptor may have in the absence of an agonist

Question 8

what is a competitive antagonist?

Answer 8

-The antagonist binds reversibly with the receptor and could be displaced by
excessive dose of agonist
-The competitive antagonist decreases the potency of the agonist but does not alter its maximal effect

Question 9

describe the dose-response curve?

Answer 9

• displaced to the right in a parallel manner in the presence of the antagonist
• the higher the concentration of antagonist the more the curve is to the right
• the maximum receptor activation doesn’t change
• x=ligand conc log y=change in receptor activation

Question 10

what is pA2 value?

Answer 10

represents the negative logarithm of the molar dose of antagonist to produce a dose ratio of 2

Question 11

Dose Ratio (DR) =

Answer 11

EC50 in presence of antagonist/EC50 in absence of antagonist

Question 12

how does a competitive antagonist work?

Answer 12

the antagonist covalently binds to the agonist binding site of the receptor

Question 13

what happened to the ‘change in receptor activation’ as the conecntration of antagonists increase?

Answer 13

it decreases

Question 14

what happened to the ‘change in receptor activation’ as the concentration of antagonists increase?

Answer 14

it decreases

Question 15

what type of antagonist does not displace the agonist?

Answer 15

• non-competitive antagonist

- The non-competitive antagonist decreases the potency and the maximal effect of the agonist

Question 16

what are the different types of other antagonists?

Answer 16

-Physiological Antagonist
-Chemical antagonist
-

Question 17

what is a physiological antagonist?

Answer 17

a ligand acts on a different type of receptors giving rise to an antagonized pharmacological effects e.g.
(1) Adrenaline antagonizes the histamine-induced allergic reactions.

Question 18

what is a chemical antagonist? antagonist?

Answer 18

occurs when a drug reduces the concentration of an agonist by forming a chemical complex

Question 19

why don’t drugs always give the same response? biological affects?

Answer 19

• different biological factors such as:
  1. Body weight and size
  2. Age and Sex
  3. Genetics - pharmacogenetics 4. Condition of health
  5. Placebo effect

Question 20

why don’t drugs always give the same response? conditions of administration?

Answer 20

1. Dose, formulation, route of administration
2. Resulting from repeated administration of drug:
   drug resistance; drug tolerance; drug allergy 3. Drug interactions:
   chemical or physical
   GI absorption
   protein binding/distribution metabolism (stimulation/inhibition) excretion (pH/transport processes) receptor (potentiation/antagonism) changes in pH or electrolytes

Question 21

what is drug interaction?

Answer 21

drug interaction can be defined as the modifications of the effects of one drug by the prior or concomitant of another drug