PHARM 3: Drug Receptor Interactions

Question 1

What id the difference between pharmacokinetics + pharmacodynamics?

Answer 1

pharmacokinetics = effect of body on the drug
(absorption, distribution, metabolism, excretion)

pharmacodynamics = effect of drug on the body
(responses, mechanism of action)

Question 2

Define Drug

Answer 2

Drug = a chemical substance that interacts with a biological system to produce a physiological effect

Question 3

What are the 4 main drug target sites?

Answer 3

1. receptors
2. ion channels
3. transport systems
4. enzymes

Question 4

What are the 2 types ion channel?

Answer 4

• voltage sensitive (e.gVSCC)

- receptor linked (e.g nAChR)

Question 5

What are the 3 ways in which drugs interact with enzymes?

Answer 5

• enzyme inhibitors
  e.g anticholinesterases
  bind to enzyme –> slows down metabolism of Ach –> elevation of Ach in synaptic cleft –> effects
• false substrates
  e. g methyldopa
• -> anti hypertensive drug
• -> nerve fibre thinks methyldop is DOPA
• -> converts to methyldopamine –> then forms false substrate
• ->which is a less good vasoconstrictor
• prodrugs
  e. g chloral hydrate
• -> Chloral hydrate needs to interact with enzyme to form active component –> trichloroethanol

Question 6

What are the 2 different mechanisms of drug action?

Answer 6

1. full agonist

2. partial agonist

Question 7

Explain the difference between full + partial agonist

Answer 7

FULL AGONIST

• reaches maximal tissue response eventually
• as you increase against conc

PARTIAL AGONIST
- can NEVER generate maximal response because it doesn’t have sufficient efficacy.

Question 8

Why is log dose response curve useful?

Answer 8

• you can see more easily where the maximal response is.

Question 9

Describe the difference between FULL + PARTIAL agonist in a log dose response curve.

Answer 9

FULL AGONISTS with lower affinity still generates maximal response, but requires higher conc

PARTIAL AGONISTS will peak before reaching maximal tissue response.

Question 10

NOTE:

- antagonists have affinity but no efficacy.

Answer 10

-

Question 11

What are the 2 main types of antagonists?

Answer 11

1. competitive
   - binds to same site as agonist on the receptor
   - so their responses = surmountable
   by increasing conc of agonist –> you can overcome competitive antagonist.

e.g atropine

2. irreversible –> causes insurmountable antagonism
   - binds more tightly to same site as agonist with covalent forces
   OR
   - binds to diff site

e.g hexamethonium.

Question 12

What is the effect of COMPETITIVE + IRREVERSIBLE antagonists?

Answer 12

COMPETITIVE:
- surmountable
(you need higher conc of agonist to generate maximal response)

IRREVERSIBLE:

• curve falls away
• cannot generate maximal response regardless of agonist conc

Question 13

What are receptors?

Answer 13

proteins within cell membs

activated by neurotransmitters or hormone

Question 14

Give example of a drug that is an agonist

Answer 14

Ach (non selective agonist)

Question 15

Give an example of a drug that is an antagonist

Answer 15

atropine (muscarinic antagonist)

Question 16

What are ion channels

Answer 16

• selective pores that allow transfer of ions does electrochemical gradient

Question 17

Give examples of ion channel drugs

Answer 17

-Local anesthetics (lidocaine)
vgsc is targeted - reduces influx of na+ ions –> less + slower propagation of AP –> less pain perceived

-Calcium channel blockers

Question 18

give examples of drugs that target transport systems

Answer 18

• Cardiac glycosides

- Tricyclic anti depressants (TCA)

Question 19

What is PPB ?

what does it do?

Answer 19

• drug binds to albumin or other protein
• creates a reservoir
• e.g warfarin, aspirin

Question 20

what is meant by an agonist

Answer 20

drug that stimulates receptor

e.g Ach, nicotine

Question 21

what is meant by an antagonist?

Answer 21

drug that interacts with the receptor and inhibits access to the receptor

e.g atropine,

Question 22

potency of drug depends on 2 properties :

Answer 22

• AFFINITY
• EFFICACY
• -> ability to create conformational change in receptor

Question 23

partial + full agonist combination results in:

Answer 23

antagonist activity against full agonist

Question 24

NOTE: selective activity -
in pharmacology, usually there is no drug that interact with only one receptor type so rather than specific, it is selective

Answer 24

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