W3- Lecture 14.2- Pharmacodynamics

Question 1

Name 4 main mechanism antagonists work by

Answer 1

Competitive antagonism
Non-competitive antagonism
Pharmacokinetics antagonism
Physiological antagonism

Question 2

Define antagonism

Answer 2

Blockade of a receptor by a drug to reduce the effect of an agonist
(0 efficacy )

Question 3

Describe a competitive antagonist
Emax ?
E50?

Answer 3

Competes for the active site
Is surmountable (more agonist needed for same effect ) 
Maximal effect of agonist unchanged
E50 shift to the right (higher dose needed)

Question 4

What is the dissociation constant for a competitive antagonist ?

Answer 4

KA

Question 5

How can affinity effect reversibility ?

Answer 5

Relatively low affinity – Reversible competitive antagonism.

High affinity – Irreversible competitive antagonism

Question 6

Name three competitive antagonists
+ receptor
+treatment

Answer 6

ranitidine (Zantac)
Histamine H2 receptor antagonist
that inhibits the production of stomach acid

propranolol (Inderal)
Beta2 adrenergic receptor antagonist
-

haloperidol (Haldol)
Dopamine D2 receptor antagonist
used in the treatment of schizophrenia

Question 7

Describe action of a non-competitive/allosteric antagonist

Answer 7

Blocks activation of receptor

By binding to the allosteric site

Question 8

Name an allosteric antagonist
+use
+receptor

Answer 8

New HIV drugs

Acting at chemokine receptor CCR5

Question 9

Describe Pharmacokinetic antagonism

Answer 9

Antagonist drug acts to increase clearance, reduce plasma concentrations and affect half life of active drug in the body.

Question 10

Describe Physiological Antagonism

Answer 10

Interaction between two drugs that initiate opposing effects via different receptors in the same target tissue.