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*Y2 LCRS Pharmacology* > Drug Receptor Interactions > Flashcards

Drug Receptor Interactions Flashcards

1
Q

What is Pharmacokinetics?

A

The effect of the body on the drug (e.g. absorption, distribution, metabolism, excretion)

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2
Q

What is Pharmacodynamics?

A

The effect of the drug on the body (responses produced, mechanism of action)

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3
Q

What is a Drug?

A

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

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4
Q

Name 4 drug target sites:

A
  • Receptors
  • Ion channels
  • Transport systems
  • Enzymes
  • All proteins
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5
Q

Where are receptors found?

A

Normally proteins within cell membranes.

Can be steroids in nucleus

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6
Q

How are receptors activated?

A

By Neurotransmitters or endogenous hormones

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7
Q

How can a receptor be defined?

A

By responding to different agonists and antagonists

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8
Q

Give 1 example of a Receptor Agonist and Agonist:

A

ACh - Agonist

Atropine - Antagonist

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9
Q

What is Atropine?

A

Muscarinic cholinoceptor antagonist used as anaesthetic premedication to dry up secretions

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10
Q

Name the 2 types of Ion channels:

A

Voltage-sensitive e.g. VSCC

Receptor-linked e.g. nAChR (Nicotinic ACh Receptor)

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11
Q

Give an example of a drug which effects Ion channels:

A

Calcium channel blockers (dipines)

Local anaesthetics (Sodium channels)

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12
Q

How does Lidocaine work?

(And other local anaesthetics)

A

Work by blocking voltage-gated sodium channels in the sensory axons

Blocking these channels in sensory axons means that fewer action potentials are propagated along those axons and so the perception of pain is reduced

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13
Q

What is the difference between a Transport system and a Receptor?

A

They don’t mediate a response, all they do is allow the NT to bind to a protein and then move it somewhere else

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14
Q

What are Transport systems?

A

Systems of carriers that transport substances against their concentration gradient e.g. glucose ions, neurotransmitters

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15
Q

Give two examples of Transport systems:

A

Na+/K+ pump

Noradrenaline uptake 1

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16
Q

Give two examples of classes of Transport system drugs:

A 
Tricyclic antidepressants (TCAs)
Cardiac Glycosides
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17
Q

Give an example of a cardiac glycoside:

What does it do?

A

Digoxin

Interacts with Na+/K+ pump

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18
Q

Which Transport system antagonist would you give a patient with heart failure, and how does it work?

A

Digoxin

  • It will slow down their Na+/K+ pump and that has a knock-on effect that INCREASES the intracellular calcium concentration
  • This, in turn, increases the force of contraction
  • So, overall, digoxin increases the contractility of the heart
19
Q

What are the three ways a drug can interact with Enzymes?

A

By being:

Enzyme Inhibitors

False Substrates

Prodrugs

20
Q

What are Enzyme inhibitors and give an example of one:

A

E.g. anticholinesterases - increases the concentration of acetylcholine in the synapse by decreasing the rate of breakdown of acetylcholine.

Neostigmine

21
Q

What antihypertensive drug is a False Substrate, and how does it work?

A

Methyldopa

It takes the place of DOPA in the NA production pathway, reducing the amount of NA produced, making Methylnoradrenaline instead.

MethylNA is worse at vasoconstriction, so hypertension is reduced.

22
Q

What is a prodrug, and give an example of how it interacts with enzymes:

A

Chloral hydrate - insomnia - chloral hydrate needs to go to the liver and be metabolised into trichloroethanol before it is effective so technically chloral hydrate must interact with an enzyme system before it becomes useful

23
Q

What can unwanted effects of drugs on enzymes be using Paracetamol as an example?

A

Paracetamol - if you take an overdose then you saturate the liver’s microsomal enzymes so another set of enzymes (P450) starts breaking down the paracetamol and the metabolites interact with the liver and kidneys

24
Q

What are three types of drugs that don’t fit the 4 target site model?

A

General Anaesthetics

Osmotic Purgatives

Antacids

25
Q

How do general anaesthetics work?

A

Dampen synaptic transmission but they do not interact with a specific transport system or receptor

26
Q

How do osmotic purgatives work?

A

Stimulate the voiding of gut contents - osmotic purgatives draw water into the stomach contents and this softens the stool and stimulates voiding

27
Q

What is an Agonist?

A

A molecule that binds to a receptor and stimulates it to generate a response (e.g. nicotine)

28
Q

What is an Antagonist?

A

Substances that interact and bind to receptors but do NOT produce a response - they just get in the way of the agonist (e.g. atropine)

29
Q

Define Affinity

A

How willingly the drug binds to its receptor

30
Q

Define Efficacy

A

Also called intrinsic activity - the ability of a drug to generate a response once it has bound to the receptor - usually involves some sort of conformational change

31
Q

Define Potency and what it depends on:

A

How powerful the drug is.

Depends on Affinity and Efficacy

32
Q

What is a full agonist?

A

An agonist that generates the maximal response

33
Q

What is a partial agonist?

A

An agonist that generates less than the maximal response

34
Q

What happens if you administer a partial and full agonist at the same time?

A

An effect similar to an antagonist because the partial agonist interferes with the ability of the full agonist to generate a response

35
Q

Define selectivity:

A

Drugs that have a preference for interacting with a particular receptor type (receptors are rarely specific - they normally interact with a few other receptors)

36
Q

What is the Structure-Activity relationship?

A

Basically, target sites are incredibly specific, so a small structural change to an agonist can make it an antagonist.

37
Q

What would a Log Dose-Response curve look like with a:

  • Full agonist
  • Full agonist with lower affinity
  • Partial agonist
A
38
Q

Describe the affinity and efficacy of an antagonist:

A

Have affinity but no efficacy

39
Q

What are the two main types of antagonist?

A

Competitive and Irreversible

40
Q

How does a competitive antagonist work?

Name two:

A

Binds to the same site as agonist, so response is surmountable. Can be overcome by adding more agonist.

Atropine and Propanalol

41
Q

How does an irreversible antagonist work?

A

It can either bind to the binding site or another site.

If binds to the binding site, it bonds strongly with covalent bonds that broken.

42
Q

Give an example of an irreversible antagonist drug and how it works:

A

Hexamethonium - irreversible nicotinic cholinoceptor antagonist (it waits until the ion channel is open and then blocks the ion channel rather than just blocking a receptor)

43
Q

What is a receptor reserve?%

A

Where not all of the receptors on a tissue need to be activated to generate a maximal response. May be as little as 1%

*Y2 LCRS Pharmacology* (20 decks)

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