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HMS120: Pharmacology > Pharmacodynamics- Receptors > Flashcards

Pharmacodynamics- Receptors Flashcards

1
Q

Define Pharmacodynamics

A

What a drug does to the body when it enters.

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2
Q

The 2 effects of drugs are:

A
  1. Systemic effect of drugs

2. Local effect of drugs

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3
Q

Systemic effect of drugs means…

A

Effect is made throughout the body. The drug has impact of entire body.

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4
Q

Give 2 examples of drugs that have a systemic effect.

A

Antihypertensive drugs - Lisinopril and Captopril

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5
Q

Local effect of drugs means…

A

Effect is limited to the area of the body, where it’s administered.

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6
Q

An example of a local effect of drugs:

A

Topical application of drugs

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7
Q

What 2 things affect the onset of the effect of drug action?

A
  1. Route of administration

2. Drug dosage

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8
Q

Give the 4 factors that affects the duration of drug action.

A
  1. Drug dosage
  2. Rate of redistribution
  3. Rate of metabolism
  4. Rate of excretion
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9
Q

The 3 sites of drug action are:

A
  1. Extracellular
  2. Cellular
  3. Intracellular
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10
Q

5 Types of Drug action are…

A
  1. Stimulation
  2. Inhibition/Depression
  3. Replacement
  4. Irritation
  5. Cytotoxic action
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11
Q

The 4 Mechanisms of action of a drug are:

A
  1. Physical action
  2. Chemical action
  3. Through enzymes
  4. Through receptors
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12
Q

The 4 Targets of drug action are:

A
  1. Enzymes
  2. Channels
  3. Transporters
  4. Receptors
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13
Q

Give 4 ways drugs produce effects in the body.

A
  1. acting on RECEPTORS.
  2. inhibiting ENZYMES.
  3. modulating or blocking ION CHANNELS.
  4. inhibiting CARRIER MOLECULES (TRANSPORTERS)
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14
Q

Explain the Lock & Key Model of Ligand-Receptor Interaction.

A

A ligand (hormone or neurotransmitter - ‘key’) bind to specific receptors (‘lock’).

This binding then unlocks the cell’s response.

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15
Q

Explain Agonists in terms of lock & key model.

A

Drugs that cause the receptor to respond in the same way as the naturally occurring substance.

  • Activates the receptor = ‘pick the lock’.
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16
Q

Explain Antagonists in terms of lock & key model.

A

Drugs that bind to the receptor, but don’t produce a response.
This results in an inhibitory effect on the naturally occurring substance.

  • Prevents activation of receptor
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17
Q

Drugs _______ enzyme mediated reactions.

A

increases/decreases

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18
Q

2 kinds of Enzyme inhibition

A
  • Reversible inhibition

- Irreversible inhibition

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19
Q

Explain Reversible inhibition.

A

Process where reversible inhibitors bind to enzyme with only non-covalent interactions (weak bonds).

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20
Q

What happens when a reversible inhibitor binds to an enzyme?

A

No reaction occurs - dynamic equilibrium

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21
Q

How is a reversible inhibitor removed?

A

Easily removed by dilution or dialysis.

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22
Q

3 types of Reversible inhibition

A
  • Competitive inhibition
  • Non-competitive inhibition
  • Uncompetitive inhibition
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23
Q

Explain Competitive inhibition

A

Process where competitive inhibitors bind only to enzymes (not enzyme-Substrate complex = ES) and inhibits enzyme to function.

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24
Q

Action of Competitive inhibitors

A

Competitive inhibitor has a similar structure to substrate so therefore competes with substrate to bind to the active site of enzyme
(forming an Enzyme-inhibitor complex = EI)

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25
Q

Examples of Competitive inhibitors

A
  • Sulfonamides
  • Methotrexate
  • Penicillin
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26
Q

Explain Irreversible inhibition

A

Process where Irreversible inhibitors bind to enzyme via covalent bonds (strong bonds = permanent) and prevents enzyme catalytic acts.

27
Q

Irreversible inhibitors act on _____

A

Some selected group of enzymes (not all).

28
Q

Examples of Irreversible inhibitors.

A

Heavy metals

  • Cadmium (Cd)
  • Arsenic (As)
  • Lead (Pb)
29
Q

Explain Non-competitive inhibition

A

Process where non-competitive inhibitors bind to both the Enzyme and Enzyme-Substrate complex (ES), hence inhibiting the enzyme to function.

30
Q

Action of Non-competitive inhibitors

A

They have no resemblance to normal substrate, therefore will:

  • work either to slow down the rate of reaction
  • or block the active site altogether and prevent enzyme function.
31
Q

Why can Non-competitive inhibitors become toxic?

A

Because they are non-selective in their actions and will destroy all enzymes.

32
Q

Examples of Non-competitive inhibitors

A
  • Mercury
  • Arsenic
  • Copper
33
Q

Drugs also target channels - mainly on 3 types which are…

A
  1. Ligand gated channels
  2. G-protein channels
  3. Direct action on channels.
34
Q

How are substrates translocated across membrane?

A

By binding to specific transporters (carriers) = Solute Carrier Proteins (SLC)

35
Q

Many drugs don’t bind directly but act through ____.

A

receptors

36
Q

What is a receptor?

A

Specific molecule, usually a protein that interacts with a specific chemical, that then causes a change in the specific molecule, causing a change in regulatory function.

37
Q

Receptors are present either on: (3)

A
  • Cell surface
  • Cytoplasm
  • Nucleus
38
Q

Examples of Receptors

A
  • Muscarinic receptors

- Nicotinic receptors

39
Q

What are Ligands?

A

Naturally occurring substances:

  • Hormones
  • Neurotransmitters (NT)
  • Mediators
40
Q

2 essential functions of Receptors

A
  1. Recognition of specific ligand molecules
    (Ligand binding domain)
  2. Transduction of signal into response
    (Effector domain)
41
Q

Drugs target receptors that are…

A

expressed to respond to endogenous ligands.

42
Q

Characteristics of drug-receptor interaction

A
  • Affinity bonds: Vander Waals
  • Specific and Selective
  • Competitive and Non-competitive
43
Q

What are the 3 different properties of drug that decide the effect of drug?

A
  • Affinity
  • Intrinsic activity (IA) / Efficacy
  • Selectivity
44
Q

What is Intrinsic activity / Efficacy?

A

Ability of drug receptor complex to produce a maximum functional response.

45
Q

What is efficacy dependent on?

A
  • Number of drug receptor complexes formed

- Efficacy of the coupling receptor activation to cellular responses.

46
Q

What is a Competitive Antagonist?

A

Any antagonist that competes with the binding of AGONIST at the binding site.

47
Q

What is a Non-competitive Antagonist?

A

Any antagonist that binds to a site on the receptor other than the AGONIST binding site.

It deactivates the receptor, preventing AGONIST from activating the receptor.

48
Q

What is Partial agonist?

A

A drug that has full affinity to receptor but with low intrinsic activity.

49
Q

Unique feature of Partial agonist drugs

A

Under appropriate conditions, partial agonists may act as an Antagonist of a full Agonist.

50
Q

What is Inverse agonist?

A

A drug that has full affinity towards the receptor, but intrinsic activity is 0 to -1 (produced effect is opposite to that of agonist).

51
Q

Action of receptor

A

Initial combination of drug with its receptors, resulting in or prevention of conformational change later on.

52
Q

Effect of receptor

A

Ultimate change in biological function as a consequence of drug action. Done through a series of intermediate steps.

53
Q

What is Receptor regulation?

A

Ongoing activity that determines density and efficacy of receptors.

54
Q

Define Supersensitive

A
  • Up regulation of receptors

- Increase in the number of receptors to a molecule (hormone or NT)

55
Q

Supersensitive can be caused by…

A

Prolonged occupation of receptors by a blocker (antagonist).

56
Q

Define Desensitize

A
  • Down regulation of receptors

- Decrease in the number of receptors to a molecule (hormone or NT)

57
Q

Desensitize can be caused by…

A

Prolonged exposure to higher conc. of an agonist.

58
Q

4 types of Drug receptors

A
  1. Ligand-gated ion channels
  2. Enzyme-linked receptors
  3. G-protein coupled receptors
  4. Nuclear (gene) receptors
59
Q

Ligand-gated ion channels are responsible for…

A

regulation of the flow of ions across cell membranes.

60
Q

Activity of Ligand-gated ion channels is regulated…

A

by binding of a ligand to the channel.

61
Q

Duration of response to Ligand-gated ion channels

A

Few milliseconds

62
Q

Important examples of Ligand-gated receptors

A
  • Nicotinic receptor

- Gamma-aminobutyric acid (GABA)

63
Q

Explain Ligand-gated ion channels/receptors - Cell surface receptors

A
  • Cell membrane requires specific ligand-gated channels for the movement of hydrophilic molecules through it.
  • Ligand binds to the receptor, then the receptor gate opens.

HMS120: Pharmacology (13 decks)

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