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PHAR221 > L7 Intro to drug action > Flashcards

L7 Intro to drug action Flashcards

1
Q

Describe a receptor

A

Receptors are specific, complex proteins. Hormones act only on target cells

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2
Q

What is pharmacology?

A

the study of the effects of drugs on the function of living systems

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3
Q

Drug Effects Result From Interaction Between ___ And (components of) the ____

A

Drug
Organism

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4
Q

Pharmacokinetics describes the fate of a drug

A

ADME
What the body does to the drug

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5
Q

Pharmacodynamics is the study and measurement of drug effects

A

What drug does to body

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6
Q

Fundamental concepts in drug action (FCDA)
A drug will not work unless it is ____

A

A drug will not work unless it is bound

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7
Q

4 protein targets

A
  1. Receptors
  2. Enzymes
  3. Carrier molecules
  4. Ion channels
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8
Q

Receptors as protein targets

A
  • Proteins that allow a chemical agent (drugs,
    hormones, neurotransmitters) to initiate a change
    in cell function
  • Receptors are the cell’s ‘sensing elements’
  • Receptors provide molecular communication between chemical agent and transduction process
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9
Q

(FCDA) Most drugs cause their effects via ___

A

Most drugs cause their effects via receptors

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10
Q

(FCDA) Different cell types have different___ ____

A

Different cell types have different receptor profiles

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11
Q

Acetylcholine example

A

High densities of muscarinic acetylcholine receptors respond to substances that act on muscarinic acetylcholine receptors

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12
Q

Noradrenaline

A

High densities of alpha-adrenoceptors respond to substances that act on alpha-adrenoceptors e.g., noradrenaline

On vascular smooth cells to cause them to contract

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13
Q

Different cell types express different types and ___ of receptor. This determines the___ and___ to which the cell responds

A

densities
hormones
neurotransmitters

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14
Q

FDCA: Drugs can mimic or ____ the actions of___ substances

A

Block
endogenous

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15
Q

Agonist and antagonist are

A

ligands

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16
Q

Ligand

A

Any molecule that bonds specifically to a receptor site of another molecule.

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17
Q

Agonist and antagonist interact with endogeneous ligands how

A

Agonist mimic the action of ligand
Antagonist block action of ligand

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18
Q

FDCA: “Receptors show ligand____”

A

selectivity

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19
Q

Receptor ligand selectivity

A
  • Each receptor type is activated by a small number of substances
  • Receptor activation requires a good 3-D “fit” between agonist and receptor
    (paracetamol doesn’t fit a vascular smooth muscle cell but phenylephrine does)
    – each drug activates a certain receptor type
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20
Q

endogenous ligand/agonist (noradrenaline) binds to receptor (alpha-adrenoceptor) causing a change in cell function (vascular smooth muscle cell contracts). What if there is an antagonist

A

Will block the binding of the ligand to receptor

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21
Q

FCDA: ___ drugs show selectivity

A

Useful

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22
Q

Selectivity is reciprocal - what does that mean

A

– each drug only binds to certain receptors
– each receptor recognises only certain drugs

23
Q

Phenylephrine

A

– binds to a-adrenoceptors in vascular smooth muscle cells – relieves nasal congestion
– binds only weakly to other receptor types
- fewer adverse effects

24
Q

cardiac cell:
adrenaline → b-adrenoceptor → increased___

A

contractility

25
Q

How most drugs cause their effects via receptors

A

Chemical agent → receptor → (in cell) signal transduction → change in cell functions

26
Q

FDCA:___ is not absolute

A

Selectivity

27
Q

Selectivity is not absolute means

A
  • Most drugs act on more than one receptor
  • Increasing dose activates other receptors
    –– adverse effects
28
Q

Diphenhydramine

A

Antagonist and prevents histamine binding
- can act on more than 1 receptor

29
Q

Diphenhydramine in vascular smooth muscle cells

A

Antagonist and prevents histamine binding
decongestant

30
Q

Diphenhydramine in salivary gland cell

A

antagonist of muscarinic acetylcholine receptors
dry mouth

31
Q

Drug-induced responses

A
  • Drugs act by binding to specific drug targets
  • Agonists bind to and activate receptors
32
Q

FDCA: “Agonist or antagonist (?) bind to and activate receptors”

A

Agonist
activate

33
Q

Transducers

A

the portion of a sensory neuron that is responsible for converting a sensory stimulus into an electrical signal

34
Q

Agonist binding to receptors

A
  • need intermolecular forces between agonist and receptors
  • Reversible
    Strong attraction forces (k+1 > k-1) → high affinity for receptor
    Week attraction forces (k+1 < k-1) → low affinity for receptor
35
Q

Agonist activating receptors

A
  • Bound agonist induces a conformational change in the structure of the receptor → it binds to and stimulates transducers
  • Bound agonist induces high degree of receptor activation → agonist has high efficacy
  • Bound agonist induces low degree of receptor activation → agonist has low efficacy
36
Q

Agonist affinity and efficacy

A

Ability of an agonist to induce a response depends on two agonist- dependent, graded properties
- affinity and efficacy

37
Q

Ability of an agonist to induce a response depends on

A

two
- agonist- dependent,
- graded properties

38
Q

Affinity

A

Tendency of agonist to bind to receptors

39
Q

Efficacy

A

Ability of agonist receptor complex to initiate a change in cell function

40
Q

Agonist-induced response example asthma

A

Asthmatic takes salbutamol
– relaxes airway smooth muscle
– eases breathing

Salbutamol + beta 2 adrenoceptor + adenylate cyclase → relaxation of air way smooth muscle

AC is tranducer

41
Q

FDCA: Drug dose is related to___ occupancy and effect

A

receptor

42
Q

Positive relationship between drug dose and

A

– number of receptors occupied
– effect produced

43
Q

With increasing concentrations of the agonist

A

– more receptors are bound and activated
– response is increased

44
Q

Organ bath

A

a chamber in which isolated organs or tissues can be administered with drugs, or stimulated electrically, in order to measure their function

45
Q

Concentration-response curves has

A
  • Measure size of response at each agonist concentration
    Plot concentration-response data as Log dose (x-axis) vs Response (y-axis)
    – log-linear or semi-log graph
    – sigmoidal shape, exhibits saturation, maximum effect is Emax
46
Q

Agonist potency

A
  • Concentration required to produce 50% of maximal agonist response (EC50)
  • The lower the EC50, the more potent the agonist
  • Potency depends on affinity and efficacy and tissue-dependent parameters (e.g., receptor density)
47
Q

EC50

A

Concentration of drug that produces 50% of maximal response

48
Q

ED50

A

The effective dose of a chemical that causes 50 percent of the individuals in a dose-response study to display a harmful, but nonlethal, effect

49
Q

Partial agonists

A
  • Partial agonists produce submaximal responses
    – low efficacy
    – low level activation

a drug that binds to a receptor and causes a response that is less than that caused by a full agonist

50
Q

Agonists with low efficacy

A

An agonist with low efficacy may act as a
– partial agonist
- partial agonist causes < maximum response
Antagonist
- tissue exposed to both low and high efficacy agonists
- competition for receptor
- full agonist binding inhibited

51
Q

Receptor antagonists
1. afinity and efficacy
2. what do they do

A

Antagonists bind to, but do not activate receptors
– have affinity, but no efficacy
- Since antagonists bind to the receptor, they compete with the agonist for the receptor
- Antagonists inhibit agonist-induced responses

52
Q

Surmountable antagonists

A
  • Bind reversibly to the receptor
  • Agonist concentration-response curves shifted
    -– no change in slope or maximum response
  • Size of the shift is proportional to the
    -– antagonist concentration
    -– affinity of the antagonist
53
Q

Insurmountable antagonists

A
  • Bind irreversibly to the receptor
    -– reduces number of receptors the agonist can occupy
  • Reduce the maximum response and slope of agonist concentration-response curve
  • The higher the antagonist concentration, the larger the response

PHAR221 (23 decks)

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