Pharmacodynamics

Question 1

Receptors?

Answer 1

Proteins that recognise + bind to endogenous signal (ligand)

Question 2

What happens when ligand binds with receptor?

Answer 2

Initiates cascade of chemical reactions

Results in biological response

Question 3

Describe an agonist

Answer 3

Binds to + activates receptor

Adds to effect of normal endogenous ligand

Question 4

Describe an antagonist

Answer 4

Binds to but does not activate receptors
When bound prevents an endogenous ligand from binding
Inhibits / reduces effect of endogenous signal

Question 5

Therapeutic Window?

Answer 5

Range of drug doses that give desired effects without toxic side effects

Question 6

Therapeutic Index (Defintion + Equation)

Answer 6

D: Measure of difference between an effective dose + toxic dose
E: minimum toxic dose in 50% of population DIVIDED BY minimum effective dose in 50% of population

Question 7

Higher therapeutic index =

Answer 7

safer drug

Question 8

Safest drugs have… (3)

Answer 8

1) Have a wide therapeutic window
2) Have no overlap between therapeutic + toxic dose-response curves
3) Have high therapeutic index

Question 9

Side effects of drugs can be due to…

Answer 9

can be due to off-target binding (drug can bind to other receptors that have a similar binding site)

Question 10

Non-selective beta blockers

Answer 10

block B1 + B2 adrenoreceptors equally (cause bronchoconstriction and reduction in heart rate

Question 11

Cardio-selective beta blocker

Answer 11

More effect on B1 adrenoreceptors

Question 12

Characteristics of completive antagonist

Answer 12

Prevents A from binding when Ant is bound to receptor

Dynamic (can bind + unbind)

Question 13

(Overcoming inhibition) If Antagonist has a higher affinity than Agonist…

Answer 13

even more A needed to overcome inhibition

Increasing [A] overcomes inhibition by reversible antagonist

Question 14

Inhibition of biological effects depends on… (4)

Answer 14

1) Relative conc of A and Ant
2) Relative affinities for receptor
3) Rate of dissociation of Ant from receptor
4) Relationship between receptor occupancy + biological effect

Question 15

What makes an antagonist irreversible?

Answer 15

Dissociation occurs at VERY LOW rate (or NOT AT ALL)

May be covalently bonded

Question 16

Describe the irreversible and competitive elements of irreversible competitive inhibitors

Answer 16

1) Higher [A] may prevent Ant from binding (competitive) 2)…but once bound it cant be displaced (irreversible)
(so further increasing [A] cannot reverse effects)