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Pharmacodynamics Flashcards

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1
Q

Pharmacodynamics

A

the study of the relationship of drug concentrations to drug effects
D+R=>DR
biological effect correlates to amount of DR

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2
Q

Receptor

A

Proteins on the surface or within cell that recognize and bind w/ specific molecules that act as chemical signals
-bind ligands

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3
Q

Ligands

A
  • drugs

- endogenous signalling molecules (ie hormones and neurotransmitters)

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4
Q

How do drugs elicit their effects-undesirable or desirable?

A

By mimicking or blocking the actions of hormones and neurotransmitters

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5
Q

Agonist

A

-drug binds to receptor and causes same effect as endogenous substance

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6
Q

Antagonist

A
  • drug binds to receptor but doesn’t produce a response

- inhibitory effect since it prevents endogenous binding

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7
Q

Kd

A
  • equilibrium dissociation constant
  • drug conc. at which 1/2 of Bmax is achieved
  • measure of the affinity of DR
  • constant-not altered by conc of drug or receptor number
  • smalle kd= higher affinity
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8
Q

Emax

A

-the max response achieved by the drug

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9
Q

ED50

A
  • the drug dose at which 50% of Emax is achieved

- POTENCY

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10
Q

Graded Dose Response Curve

A

-infinite number of intermediate states

eg vessel dilation, bp change, heart rate change

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11
Q

Quantal dose response curves

A
  • all or none

eg. death, pregnancy, cure, pain relief, effect of given magnitude

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12
Q

Under what circumstances are quantal dose response curves particularly useful?

A
  • to describe pop response to drugs

- based on plotting cumulative frequency distribution of responders against the log drug dose

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13
Q

Potency

A
  • ED50

- related to the amount of agonist needed to produce an effect of a given magnitude

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14
Q

Efficacy

A

Emax

-related to the max effect that can be achieved w/ a particular agonist

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15
Q

Full agonist

A
  • high potency, max efficacy

- reduced potency, max efficacy

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16
Q

Partial agonist

A
  • high potency, reduced efficacy
  • reduced potency, reduced efficacy
  • have a lower functional impact on the receptor
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17
Q

Max. efficacy is defined by the max. effect achieved with ?

A

the endogenous R agonist

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18
Q

Constitutive Receptor Activation

A
  • agonist binding induces conformational change in the receptor from inactive to active
  • agonists stabilize the active state
  • spont. dissociation of agonist returns receptor to inactive state
  • conformational change to active state can also occur spot in the absence of agonist
  • -> constitutive receptor activation
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19
Q

Inverse Agonist

A
  • stabilizes the inactive state
  • destabilizes the active state
  • constitutive receptor activation
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20
Q

Draw diagram demonstrating experimental apparatus to measure constitutive receptor activity

A

Pharmacodynamics

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21
Q

What is the effect of agonists on receptors with constitutive activity?

A

-has an independent impact upon receptor activity

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22
Q

What is the effect of antagonists on receptors with constitutive activity?

A

-impacts receptor activity only in the presence of agonist (lacks efficacy)

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23
Q

What is the effect of inverse agonists on receptors with constitutive activity?

A
  • has an independent impact upon receptor activity

- produces an effect opposite to agonist

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24
Q

Chemical Antagonism

A

Direct interaction of 2 substances in solution such that the effect of one or both is lost

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25
Example of Chemical Antagonism
- protamine (acidic anticoagulant) and heparin (basic anticoagulant) - loss of activity of both drugs
26
Physiological Antagonism
Indirect interaction of 2 substances with opposing physiological actions
27
Example of Physiological Antagonism
- histamine, lowers bp through vasodilation (H1 R) | - epinephrine raises bp through vasoconstriction (alpha1 adrenergic R)
28
Pharmacological Antagonism
- bind to receptors but do not activate signal transduction mechanisms - biological effects from blocking ability of agonist to bind/activate R
29
Example of Pharmacological Antagonism
cimetidine blocks binding of histamine to H2 R resulting in lower gastric acid secretion
30
Competitive Antagonists
-bind reversibly to the receptor -inhibition can be overcome by increasing agonist conc AFFECTS AGONIST POTENCY
31
Non-competitive Antagonists
- bind irreversibly (e.g. covalently) to the R or reversibly/irreversibly to a site on the receptor different from agonist (allosteric) - inhibition cannot be overcome by increasing agonist conc - AFFECTS AGONIST EFFICACY
32
Draw the dose response curve for agonist in the presence of competitive antagonist
Pharmacodynamics
33
Draw the dose response curve for agonist in the presence of non competitive antagonist
Pharmacodynamics
34
ED50 of antagonists
- the antagonist dose at which 50% of Emax is achieved | - aka potency, ID50, IC50
35
Emax of antagonists
- max biological effect achieved by the antagonist | - NOT a measure of efficacy
36
T or F: majority of endogenous receptor ligands are full agonists
True
37
T or F: endogenous inverse agonists are common
False-rare
38
What is an example of an endogenous inverse agonist?
Agouti Related peptide (AGRP) - reduces constitutive R activity of melanocortin R - increases food intake and reduces energy expenditure
39
T or F: Endogenous pure antagonists are rare
True
40
What is an example of an endogenous pure antagonist?
Kynurenic acid - NMDA receptor antagonist - physiological role unclear but may play a role in neurotransmission and neuropathologies
41
? is a full agonist that mimics epinephrine at cardiac Beta1R
Isoproterenol
42
? is a partial agonist that mimics endogenous endorphins at u opiod R
-buprenorphine
43
Why is buprenorphine safer than morphine
-reduced risk with of respiratory depression with overdose
44
Superagonists
>100% Emax | -uncommon in clinical practice
45
Drug Desensitization
-effect of a drug often diminishes when given continuously or repeatedly
46
Receptor Mediated Desensitization (2)
- loss of receptor fxn | - reduction of receptor number
47
How does loss of receptor function cause desensitization?
- rapid desensitization due to change in receptor conformation - usually due to feedback of cellular effects of agonist
48
How does reduction of receptor number cause desensitization?
- slower, long term desensitization due to change in receptor number - usually due to feedback of cellular effects of agonist
49
What is an example of desensitization caused by loss of receptor function?
Phosphorylation of specific amino acids in GPCRs blocks coupling to G proteins
50
What is an example of desensitization caused by reduction of receptor number?
-Phosphorylation of specific aa's in GPCRs causes removal from cell surface
51
What are the 3 types of non receptor mediated desensitization?
1. reduction of receptor coupled signalling components 2. increased metabolic degradation 3. biological adaptation
52
How does reduction of receptor coupled signalling cause desensitization?
-depletion of signaling molecules required for biological response
53
What is an example of reduction of receptor coupled signalling desensitization?
-prolonged stimulation of G-protein coupled receptors can lead to depletion of intracellular secondary messengers ie cellular stores of ATP depleted by prolonged cAMP production
54
How does increased metabolic degradation cause desensitization?
- increase in the rate of metabolism and/or elimination of drug - lowers plasma drug concentrations
55
What is an example of desensitization caused by increased metabolic degradation?
-barbiturates induce the expression of metabolic enzymes that degrade these drugs
56
How does increased physiological adaptation cause desensitization?
- reduction or amelioration of drug effects due to opposing homeostatic response - very few well characterized mechanisms
57
What are the 3 adverse drug effects?
1. side effects 2. toxic reaction 3. allergic reaction
58
Side Effect
- dose dependent - not directly related to desired effect of drug - action of drug at other sites to produce undesirable effects
59
Toxic Reaction
- dose dependent - directly related to desired effect of drug - excessive action of drug at intended target site
60
Allergic Reaction
- not dose dependent - not related to desired effect of drug - immunologic response to drug (largely unpredictable)
61
What is the desirable therapeutic effect of cyclosporine?
- promotes survival of transplanted organs | - magnitude of effect is dose dependent
62
What are the toxic effects of cyclosporine?
- increased susceptibility to infection - consequence of intended pharmacological action (immunosuppression) - dose dependent
63
What are the side effects of cyclosporine?
- kidney damage - not related to intended pharmacological activity - dose dependent
64
What are the allergic effects of cyclosporine?
- rash, hives, itching, breathing difficulties - not related to intended pharmacological activity - not dose dependent
65
T or F: the nature of the drug determines toxicity
False-the amount determines toxicity
66
Therapeutic Index
-a measure of drug safety -dose required for a toxic/ adverse drug effect vs that required for beneficial effect TI=Toxic ED50/Beneficial ED50 -larger TI indicates a clinically safer drug
67
Therapeutic Window-Relationship to blood levels
-considers a range of blood concentrations assoc. with toxic effects, therapeutic benefit or lack of effect within a pop.
68
Therapeutic Window-Relationship to dose
-considers the range of dosages assoc. with toxic effects, therapeutic benefit or lack of effect within a pop.

Pharmacology (9 decks)

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