Drug action

Question 1

Ligands

Answer 1

Ligands = molecules that bind to receptors

Question 2

what do drugs bind to?

Answer 2

proteins eg
receptors
enzymes
ion channels
transporters
- Circulating proteins(plasma protein carriers)
- DNA
- Bacterial cell walls

Question 3

Agonist

Answer 3

Agonist = mimics effect (affinity and efficacy)

Agonist: drug that activates receptors to result in either stimulation or inhibition of the function of various types of cells and organs.

Question 4

Antagonist

Answer 4

Antagonist = blocks effect (affinity but no efficacy)

Antagonist: drug that prevents receptor activation by agonists

Question 5

Inverse agonist

Answer 5

Inverse agonist = produces the opposite effect that would be produced by an agonist or natural neurotransmitter

Question 6

Partial agonist

Answer 6

Partial agonist = cannot achieve maximal response even when it is fully bound

Question 7

which type of drug competes with natural ligand to block response?

Answer 7

competitive antagonist

Question 8

what does a non comp antagonist do?

Answer 8

binds to another site and lowers response to give partial signal

Question 9

can drugs interact with receptors on their own to produce a response?

Answer 9

no. Drug/receptor interactions require coupling to another mechanism

• Ion channels fastest
• G proteins mid (GPCR 7 transmembrane receptors)
• Enzymes slowest (eg phosphatases and kinases)
• Gene transcription etc

Question 10

example of a ion channel receptor

Answer 10

nicotininc ach receptor

Question 11

example of a gpcr

Answer 11

muscarinic ach receptor

Question 12

afffinity

Answer 12

Affinity = tightness of drug binding

Question 13

Occupancy

Answer 13

Occupancy = duration of binding

Question 14

Efficacy

Answer 14

Efficacy = effectiveness at producing response

Question 15

relationship between affinity and Kd

Answer 15

High affinity low dissociation constant (Kd)

Question 16

what is the law of mass action?

Answer 16

Follow Mass-Action Law: rate of reaction is DIRECTLY proportional to the concentration of the reactants, however, there is a limit. This limit is called the point of saturation

There are only so many receptors on each cell to which a drug can bind. Point of saturation refers to the point at which every receptor is bound.

higher conc of drug means more receptors occupied at any one time and more response will be achieved

Question 17

for law of mass action, is the graph linear or non linear

Answer 17

can be both.

Question 18

know what a graph of a partial agonist looks like

Question 19

how do drugs change enzymatic action?

Answer 19

competitive - substrate antagonism (antagonism because the drug BLOCKS the active site, preventing substrate)

non competitive substrate inhibition

Question 20

examples of enzyme drugs

Answer 20

aspirin (irreversible)
simvastatin (reversible enzyme modification)

Question 21

how does local anaesthetic work?

Answer 21

PART 1
- Blocks axonal sodium entry
- prevents depolarization
- prevents AP propogation
- prevents perception of pain

PART 2
- stabilizes it in the inactivated conformation

Question 22

3 STATES of sodium channels

Answer 22

resting, open, inactivated

Question 23

basic structure of LA

Answer 23

• Aromatic side chain
• Ester/amide
• Basic side chain

Question 24

amide or ester more stable?

Answer 24

amides more stable, longer half life

Question 25

common dental LA

Answer 25

LIDOCAINE ARTICAINE

Question 26

Half life of lidocaine and articaine

Answer 26

lidocaine rapid onset, 2h half life articaine rapid onset, 30min half life

Question 27

why are vasoconstrictors used with la?

Answer 27

to prevent LA from escaping into systemic circulation