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Pharmacology I > 2. Drug-receptor interactions. Dose-response relations, therapeutic concepts > Flashcards

2. Drug-receptor interactions. Dose-response relations, therapeutic concepts Flashcards

1
Q

At what threshold would the effect of a drug be seen?

A

When sufficient numbers of receptors are occupied we may see effect

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2
Q

The fraction of receptors in each state are dependent on…

A

Dissociation constant Kd

  • Concentration of ligand at which 50% of available receptors are occupied*
  • Lower Kd indicates a tighter drug-receptor interaction (high affinity)*
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3
Q

Pharmacodynamics of a drug

A

Relationship between dose of drug and organism’s response to that drug

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4
Q

Graded dose-response curve

A

Demonstrates effect of a drug as a function of its dose

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5
Q

Max drug-receptor binding occurs when…

A

[LR] (cc of ligand-receptor complexes)

=

[Ro] (cc of receptors)

or [LR]/[Ro]=1

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6
Q

EC50

A

Potency of drug (cc at which drug elicits 50% of its max effect)

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7
Q

Emax

A

Efficacy (max response produced by a drug)

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8
Q

Potency & efficacy relationship

A

Not intrinsically related, a drug can be extremely potent but have little efficacy & vice versa

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9
Q

Quantal dose-response relationship

A

Describes cc of a drug that produces a given effect in a population

  • Goal is to generalise a result to a population rather than examine grade of effect of different drug doses on a single individual
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10
Q

ED50

A

Dose that produces therapeutic response in 50% of population

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11
Q

TD50

A

Toxic dose in 50% of the population

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12
Q

LD50

A

Death in 50% of the population

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13
Q

Agonist

A

Drugs that bind to its receptor and favour active receptor conformation

  • More potent drugs are those that have a higher affinity for their receptors
  • More efficacious drugs are those drugs that cause a higher proportion of receptors to be activated
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14
Q

Partial agonist

A

Binds to a receptor at its active site but produces only a partial response

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15
Q

Because partial and full agonists bind to the same site on a receptor…

A

A partial agonist can reduce response produced by a full agonist

(Competetive agonist)

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16
Q

Inverse agonist

A
  • The receptor must have a basal level activity in the absence of any ligand
  • Decreases activity below basal level
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17
Q

Antagonist

A

Drug that prevents activation of receptor by the agonist

  • Can bind to active/allosteric site of receptor for agonist
  • Reversible/irreversible
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18
Q

Competetive antagonist

A

Reduces the potency of the agonist

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19
Q

Non-competitive antagonist

A

Reduces efficacy of agonist

20
Q

Chemical non-receptor antagonist

A

Inactivate an agonist before it has the opportunity to act, by chemical neutralisation

21
Q

Physiological non-receptor antagonist

A

Cause a physiological effect opposite to that induced by an agonist, by blocking or activating a receptor

22
Q

Therapeutic window

A

Range of doses of a drug that elicits a therapeutic response, without unacceptable adverse effects in a population

  • Can be quantified by therapeutic index
23
Q

Therapeutic index =

A

[LD50]/[ED50]

  • Provides a single number that quantifies the relatively safety margin
  • Large TI = Large/wide therapeutic window, TI = 10
  • Small TI = Small/narrow therapeutic window, TI = 5
24
Q

What is shown?

A

Continuous dose-response curve

25
Q

What is shown?

A

Quantal dose-response curves

Effects on the population

26
Q

Affinity

A

The degree to which a drug tends to combine with a receptor

27
Q

Efficacy

A

The desire to produce a successful result

28
Q
A

Full agonist: Heroin and others

29
Q
A

Partial agonist - Buprenorphine

30
Q

Title the figure

A

Occupancy model

31
Q

Title the figure

A

Two-state model

32
Q
A

Full agonist

33
Q
A

Partial agonist

34
Q
A

Neutral antagonist

35
Q
A

Inverse agonist

36
Q

Give an example of inverse agonists

A

Antihistamines

37
Q
A

Full agonist

38
Q
A

Partial Agonist

39
Q
A

Partial agonist

40
Q

Examples of competitive antagonists

A
  • Morphine
  • Benzodiazepines
  • MACh
41
Q

Give example of noncompetitive antagonists

A
  • Ketamine (on NDMA receptors)
42
Q

When looking at a dose-response curve, a drug is not safe if…

A

The LD50 crosses with the ED50

43
Q

Compare:

  1. Which is more potent, butorphanol or morphine?
  2. Which is more effective, butorphanol or morphine?
A
  1. Butorphanol
  2. Morphine
44
Q

Full agonist: Efficacy + affinity

A

High efficacy + affinity

45
Q

Full antagonist: Efficacy + affinity

A

High affinity; no efficacy

46
Q

Partial agonist: Efficacy + affinity

A

High affinity; partial activation of receptor

47
Q

Inverse agonist: Example

A

Antihistamine

Reverses the function of the agonist

Pharmacology I (19 decks)

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