Drug receptor interactions

Question 1

What is the definition of a drug?

Answer 1

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

Question 2

What are the 4 different drug target sites?

Answer 2

Receptors
Enzymes
Ion Channels
Transport Systems

Question 3

Where are most receptors found?

Answer 3

They are exposed on the cell surface so drugs can easily get to them

Question 4

What is the exception to the where most receptors are found?

Answer 4

Steroid receptors are found in the nucleus

Question 5

What are examples of receptor affecting drugs? Name an agonist and an antagonist

Answer 5

Ach (agonist)

Atropine (antagonist)

Question 6

How are receptors activated?

Answer 6

NT or hormones

Question 7

What are examples of drugs that affect ion channels?

Answer 7

LA (local anaesthetic)

Ca2+ Channel Blockers (-dipines)

Question 8

What are the two types of ion channels?

Answer 8

Voltage sensitive (VSCC)
Receptor linked nAChR (nicotinic acetylcholine receptor)

Question 9

What are ion channels?

Answer 9

Selective pores that allow transfer of ions down an electrochemical gradient

Question 10

What are transport systems?

Answer 10

They transport against a concentration gradient eg glucose uptake into cells, ion transporters and neurotransmitters

Question 11

What are example of drugs that affect transport systems

Answer 11

Tricycle antidepressants TCAs

Cardiac glycosides

Question 12

What is an example of what TCAs do?

Answer 12

They can slow down the NA reuptake and deactivation therefore allowing longer time for noradrenaline action to take place.

Question 13

What are enzymes

Answer 13

Catalytic proteins that increase reaction rate

Question 14

What are examples of drug interactions with enzymes?

Answer 14

Enzyme inhibitors eg anticholinesterase
False substrates eg methyldopa
Prodrugs eg chloral hydrate or trichoroethanol

Question 15

What is similar within receptor families and how many families are there?

Answer 15

They have similar structures and transduction systems. There are 4 families

Question 16

What are examples of non specific drug actions?

Answer 16

Antacids - all basic eg Mg/Al hydroxide

Osmotic purgatives - draw water into gut

Question 17

What are non specific drug actions for?

Answer 17

Treating patients using the physiochemical properties of the drug

Question 18

What does plasma protein binding react to a drug and what is the result?

Answer 18

The drug binds to albumin and causes the inactivation of the drug, providing a reservoir of inactive drug. There is no physiological reaction and is used as drug storage within the body

Question 19

What is an agonist?

Answer 19

A ligand - any substance that binds to and stimulates a receptor eg ach or nicotine

Question 20

What is an antagonist?

Answer 20

Something that binds to a receptor but doesn’t cause a reaction therefore blocks the receptor and decreases activity eg atropine or hexamethonium

Question 21

What does the potency of a drug depend on?

Answer 21

Affinity

Efficacy

Question 22

What does affinity mean?

Answer 22

The binding property of a receptor

Question 23

What does efficacy mean?

Answer 23

The ‘intrinsic activity’ to do smth to generate a response eg conformational change of a receptor

Question 24

What is a full agnonist

Answer 24

It can generate the full response of a receptor

Question 25

What is a partial agonist

Answer 25

It can never generate the full response of a receptor

Question 26

What happens when you use a partial and a full agonist at the same time?

Answer 26

Partial agonist will generate a slight antagonist effect

Question 27

What is selectivity?

Answer 27

The degree to which a drug acts on a given site relative to other sites

Question 28

Why is the term selectivity used instead of specificity?

Answer 28

Because specificity means it binds to only one receptor but in high enough doses, a drug will bind to several different receptors and cause some of the unwanted side effects of drugs

Question 29

What is the key factor of an antagonist that is different to agonists?

Answer 29

Antagonists have affinity but no efficacy

Question 30

What are the 2 types of receptor antagonists

Answer 30

Competitive and Irreversible

Question 31

What is the key property of a competitive antagonist?

Answer 31

It binds to the same site as the agonist, and is therefore surmountable (if high conc agonist then it can overcome the antagonist)

Question 32

How can you see surmountable on dose response curve?

Answer 32

D-R curve shift to right

Question 33

What are examples of receptor antagonists?

Answer 33

Atropine | Propranolol (beta blocker)

Question 34

What is the key property of an irreversible antagonist?

Answer 34

If do bind to same site as agonist, binds more tightly than the agonist. OR binds at a different site. Both are insurmountable (and drugs last longer)

Question 35

What is an example of an irreversible antagonist?

Answer 35

hexamethonium