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Year 2 Pharm > 3 - Drug-receptor interactions > Flashcards

3 - Drug-receptor interactions Flashcards

1
Q

Define Pharmacokinetics and Pharmacodynamics.

A

Pharmacokinetics – the effect that the body has on the drug (ADME)
Pharmacodynamics – the effect of the drug on the body

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2
Q

Define ‘drug’.

A

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

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3
Q

State the four main target sites for drugs.

A 
Receptors 
Ion Channels 
Transport Systems
Enzymes
(note that these are all proteins)
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4
Q

What are receptors (where are they found)?

A

proteins within cell membranes (usually - exception=steroid receptors) activated by neurotransmitter and hormones

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5
Q

Define ligand

A

any molecules that interact with receptors

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6
Q

Give an example of a drug that target receptors and state what it is used for

A

atropine - muscarinic cholinoreceptor antagonist - used as an anaesthetic premedication to dry up secretions

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7
Q

What are the two types of ion channels? Give an example of each

A

Voltage-Gated e.g. VGSCs

Receptor Linked/ligand-gated - e.g. nAChr

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8
Q

How do drugs target ion channels?

A

interact with the actual ion channels, not the receptors

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9
Q

Give an example of a drug that acts by targeting ion channels

A
  • local anaesthetics - block VGSCs (by lodging inside them) in the sensory axons
  • calcium channel blockers
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10
Q

What is meant by transport systems as a target site for drugs?

A

Systems of carriers that transport substances against their concentration gradient
e.g. glucose ions, neurotransmitters
NOT receptors - don’t mediate a response, they only allow the NT to bind to a protein and then move it somewhere else

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11
Q

Give some example of transport systems

A

o Na+/K+ pump

o Noradrenaline uptake 1

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12
Q

Give an example of a drug that acts on transport systems.

A
  • Tricyclic antidepressants
  • Cardiac glycosides – it slows down the Na+/K+ pump —> increases intracellular calcium ion concentration—> increased force of contraction
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13
Q

What are the three ways in which drugs can interact with enzymes?

A
  • Enzyme inhibitors
  • False transmitter
  • Prodrugs (e.g. chloral hydrate)
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14
Q

Give an example of an enzyme inhibitor

A

neostigmine - inhibits acteylcholinesterases

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15
Q

Give an example of a false transmitter

A

methyldopa (an antihypertensive)

replaces DOPA in the NA pathway -> reduces the amount of DOPA being converted to dopamine (methyl NA produced)

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16
Q

Give an example of the prodrug pathway of enzyme-drug interaction

A

chloral hydrate (sleeping tablet) - insomnia

chloral hydrate needs to go to the liver and be metabolised into trichloroethanol before it is effective

17
Q

What is a common example of the unwanted effects of drug interaction with enzymes?

A

Paracetamol overdose – this will saturate the microsomal enzymes in the liver so the paracetamol is then broken down by another set of enzymes (P450) which generates toxic metabolites

18
Q

Name three groups of drugs that are exceptions to the four target site rule and produce responses due to their physiological properties

A

General anaesthetics – reduce synaptic transmission without interacting with transport systems or receptors
Antacids – these are basic so they simply neutralize some of the stomach acid
Osmotic purgatives – draw water into the bowel due to its physicochemical properties

19
Q

Define agonist.

A

A molecule that binds to a receptor and generates a response

20
Q

Define antagonist.

A

A molecule that binds to a receptor but do NOT generate a response

21
Q

Define potency. What is it dependent on?

A

How powerful the drug is
It depends on affinity (how willingly the drug binds to the receptor) and efficacy (the ability of a drug to generate a response once bound)

22
Q

What is a full agonist?

A

An agonist that generates a maximum response

23
Q

What is a partial agonist?

A

An agonist that generates a less than maximum response

24
Q

What is selectivity?

A

Drugs have a preference for binding to certain receptors (it is rarely specific – they normally bind to a few different receptors)

25
Q

What is the difference between full agonists with a high affinity and full agonists with a lower affinity?

A

Full agonists with a lower affinity can still generate a maximum response but requires a higher dose than the full agonist with lower affinity

26
Q

Describe antagonists in terms of affinity and efficacy.

A

Antagonists have affinity but NO efficacy

27
Q

What are the two types of antagonist?

A

Competitive – they bind to the same site as the agonist on the receptor – they are surmountable

Irreversible – could bind to the same site as the agonist but will bind more tightly with covalent forces so that they can’t be moved – some irreversible antagonists will bind to sites different to the site that the agonist binds to – insurmountable

28
Q

Give examples of the 2 types of antagonist

A

competitive

  • atropine - competitive muscarinic cholinoreceptor antagonist
  • propanolol

irreversible
- hexamethonium - irreversible nicotinic cholinoreceptor antagonist

29
Q

What effect do the two types of antagonist (competitive and irreversible) have on dose-response curves?

A

Competitive – shifts the D-R curve to the RIGHT
Irreversible – shifts the D-R curve to the RIGHT and LOWERS the response elicited (it can no longer generate a full response)

30
Q

What is receptor reserve?

A

In some tissues, not all the receptors need to be stimulated to generate a maximum response (sometimes as little as 1% of receptors may need to be activated)
This increases the sensitivity of the tissue to the agonist

31
Q

True or false: full agonists that are selective for a given receptor will have the same efficacy.

A

True

They are full agonists so they all elicit a maximum response hence they have the same efficacy

32
Q

Calcium channel blockers drugs end in ______

A

-dipine

33
Q

All drug target sites are ________ .

A

PROTEINS

Year 2 Pharm (9 decks)

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