Mechanism of Drug Action

Question 1

What are the 4 types of drug antagonism?

Answer 1

• receptor blockade
• physiological antagonism
• chemical antagonism
• pharmacokinetic antagonism

Question 2

What is receptor blockade?

Answer 2

An antagonist binding to a receptor site and preventing agonist binding

Question 3

What are the 2 type of receptor blockade?

Answer 3

• competitive

- irreversible

Question 4

What does use dependency mean?

Answer 4

The more active the tissue of the drug target, the more effective the drug will be
Refers to ion channel blockers

Question 5

How do local anaesthetics work?

Answer 5

• they bind to the inside of an ion channel after they open
• the more the channels are open the higher the chance that they will be blocked by LAs
• they selectively act on nociceptor neurones (pain conducting fibres that fire more often than normal neurones)

Question 6

What is physiological antagonism?

Answer 6

Two drugs act at different receptors, to have opposite effects in the SAME tissue

Question 7

Give an example of physiological antagonism

Answer 7

NA binds to vasculature causing vasoconstriction

Histamine would result in vasodilation

Question 8

What is chemical antagonism

Answer 8

The interactions of substances in a solution

Question 9

Give an example of chemical antagonism

Answer 9

Dimercaprol is a chelating agent- forms heavy metal complexes that are rapidly excreted from the kidneys
-helps with lead poisoning

Question 10

What is pharmokinetic antagonism?

Answer 10

One drug reduces the concentration of the other at the site of its action
- may reduce absorption, increase metabolism, increase excretion of the other drug

Question 11

Give a clinically important example of pharmacokinetic antagonism?

Answer 11

barbiturates lead to an increase production in microsomal enzymes, another drug that is metabolised by these enzymes will have reduced effects due to this increase

Question 12

What is drug tolerance?

Answer 12

The gradual decline in responsiveness to a drug with repeated administration

Question 13

What are the 5 causes of drug tolerance?

Answer 13

• pharmokinetic factors
• loss of receptors
• conformational change of receptors
• exhaustion of mediator stores (amphetamines)
• physiological adaptation

Question 14

What are the 4 main receptor families classified by?

Answer 14

• molecular structure

- signal transduction systems

Question 15

What are the 4 main receptor types?

Answer 15

Type 1: ionotropic receptor
Type 2: G-protein coupled
Type 3: tyrosine-kinase linked
Type 4: intracellular steroid

Question 16

What is a distinguishing feature of type 1 receptors?

Answer 16

• 4/5 subunits
• alpha helicies
• external binding domain that will open an ion channel

Question 17

What is a distinguishing feature of type 2 receptors?

Answer 17

• 1 subunit

- 7 transmembrane domains

Question 18

What is a distinguishing feature of type 3 receptors?

Answer 18

• kinase linked
• single protein
• 1 transmembrane domain
• intracellular domain inside the cell

Question 19

What is a distinguishing feature of type 4 receptors?

Answer 19

-zinc fingers