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Pharmacology > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

What are the different names a drug can have and what one should we care about?

A

Chemical name, generic name, commercial name

We need to know the generic name

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2
Q

What do organisms rely on to control tissue function?

A

Multicellular organisms rely upon intercellular signalling molecules to control tissue function

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3
Q

Features of receptors for drug interactions (4)

A

-The signalling molecules interact with proteins (receptors) in the plasma membrane to regulate biochemical pathways in the cytoplasm

-Each cell typ expreses a unique selection of receptors
-More than 1k PM receptors are known in 20 families
-Most drugs act by stimulating or blocking membrane receptors

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4
Q

What are the three things drugs need to possess adequately to interact with receptors?

A

Size, charge, shape and atomic composition

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5
Q

What are the lower and upper limits related to drug size?

A

Lower limit = minimum size needed to impart SPECIFICITY of action (100 MW)

Upper limit = size limit allowing reasonable movement in the body to sites of action (1000MW)

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6
Q

What is special about the administration of large drugs?

A

They must be administered directly into the compartments where the target receptors are located (bc they are too big to be able to leave otherwise)

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7
Q

How do drugs and receptors interact related to chemical forces or bonds?

A

Drugs that interact w receptors through WEAK BONDS are MORE SELECTIVE

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8
Q

What is drug affinity

A

Relative ability to bind to the receptor

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9
Q

What are the two common types of bonds and their features?

A

Electrostatic
-weaker than covalent
-includes electrostatic, hydrogen, van der wal bonds
-Many D-R interactions involve this bond

Hydrophobic
-Usually quite weak
-Probs most important with lipid interactions and highly lipid soluble drugs
-Many D-R interactions involve these bonds

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10
Q

Which type of bond has the weakest/more selectivity?

A

Hydrophobic

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11
Q

What bonds are important for highly lipid soluble drugs?

A

Hydrophobic

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12
Q

What do many drugs exist as?

A

Enantiomers (left and right handed versions of molecule)

Usually one of them is more portent and reflects a better fit with a receptor

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13
Q

Why do drugs modify signal transduction after binding to receptors?

A

To initiate, enhance, diminish, and terminate cellular chemical pathways

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14
Q

What do the effects of binding depend on?

A

Effects depend on actions of effector proteins and often second messengers that modulate cellular targets

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15
Q

What is drug effect proportional to?

A

Proportional to the percentage of receptors occupied by drug

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16
Q

What does the fraction of drug receptors that are occupied depend on?

A

Fraction of drug receptors occupied by drug is dependent on drug concentration in ECF

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17
Q

What are the five main mechanisms of transmembrane signalling that account for the majority of drug effects?

A
  1. Lipid-soluble drug binds to cytoplasmic receptor
  2. Transmembrane enzyme
  3. Transmembrane non-enyzme
  4. Drug binds to and opens/blocks an ion channel
  5. G-protein coupled receptors
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18
Q

Feature of cytoplasmic receptors and how it works

A

-Receptor possess a DNA binding domain as well as a ligand-binding site

D-R complex translocates to nucleus -> binds to response elements -> MODULATE GENE TRANSCRIPTION

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19
Q

Examples of lipid soluble drugs that bind to cytoplasmic receptors

A

Steroids (progesterone, estrogen, glucocorticoids)

Biological effects persist after drug has left body (hours,days)

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20
Q

How do transmembrane enzymes work?

A

D-R complex activates enzymatic activity on cytoplasmic face of receptor

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21
Q

How do transmembrane non-enzymes work?

A

Receptor activation allows mobile enzymes to bind to the cytoplasmic face of the receptor, activating the enzyme

includes cytokine receptors

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22
Q

What are the key neurotransmitters that modulate ion channels? How they work?

A

-GABA, 5-HT, glutamate

Effects are very rapid and they transduce signal across a membrane by allowing ions to cross membrane and alter cell excitability

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23
Q

What is the most abundant receptor type

A

G protein coupled receptor

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24
Q

How do GPCR work?

A

THey bind to a family of heterotrimeric GTP binding regulatory proteins termed G proteins. Activation results in exchange of GDP for GTP and subsequent downstream effects

25
Q

What are second messengers?

A

Cytoplasmic molecules that translate D-R interaction into a change in cellular activity.

26
Q

What does most second messengers entail

A

Entail reversible phosphorylation of key targets which allows for amplification of signal and flexible regulation of signalling

27
Q

What is the purpose of giving drugs therapeutically? (2)

A

Stimulate receptors in hypofunctional states

Block receptors in hyperfunctional states

28
Q

What does an agonist do?

A

Activates receptor = cellular response

29
Q

What does an partial agonist do?

A

Agonist that is not able to fully activate the receptor

30
Q

What does an antagonist do?

A

Binds to but doesnt activate the receptor = prevents agonists from stimulating receptor

31
Q

What does an inverse agonist do?

A

Reduces basal activity of receptor

32
Q

What is the dose response curve?

A

Its a depiction of the observed drug effect (% maximal response) as a function of drug concentration

33
Q

What is potency?

A

The concentration of drug required to produce a given effect

34
Q

What defines potency?

A

Normally defined by the half-maximal effective concentration (EC50)

35
Q

How can you measure relative potency?

A

Relative potency of different drugs acting at the same receptor can be measured by comparing EC50 values

36
Q

Are the most potent drugs the most efficacious?

A

Not necessarily

37
Q

When is low potency a concern?

A

Its a concern if the volume of the required dose is too large to be convenient

38
Q

What is efficacy?

A

The magnitude of the cellular response produced when all the receptors of a given type are occupied by the ligand

Defined by maximal response (Emax) of the drug

39
Q

What gives a measure of relative efficacy?

A

Comparison of maximal responses of drugs acting at the same receptors

40
Q

What is the parameter of greatest interest to the clinician

A

Efficacy

41
Q

Why do hormones typically have a lag time for their effects?

A

Because there is a time required for the synthesis of new proteins.

42
Q

What is the main characteristic of a competitive receptor antagonist?

A

It has affinity for the receptor but no efficacy, competing with the agonist at the site.

43
Q

How can the effects of a fixed dose of antagonist be overcome?

A

By increasing the concentration of the agonist.

44
Q

What effect does a competitive antagonist have on the dose-response curve?

A

It produces a parallel rightward shift in the dose-response curve

45
Q

What happens to the EC50 value in the presence of a competitive antagonist?

A

The EC50 value increases (is larger), indicating decreased potency of the agonist.

46
Q

Does the competitive antagonist change the Emax of the agonist?

A

No, there is no change in Emax

47
Q

How does a non-competitive antagonist bind to the receptor?

A

It binds irreversibly to the receptor or dissociates very slowly.

48
Q

Can a higher concentration of agonist overcome the effects of a fixed dose of non-competitive antagonist?

A

No, a higher concentration of agonist cannot overcome the effects.

49
Q

What happens to Emax in the presence of a non-competitive antagonist?

A

Emax is reduced, meaning the agonist’s efficacy is decreased.

50
Q

Is there always a change in EC50 when a non-competitive antagonist is present?

A

There may or may not be a change in EC50.

51
Q

What is the process of an allosteric antagonism?

A

-Primary ligand/drug binds to main binding site on receptor
-Allosteric antagonist binds to a different site on the receptor, a conformational change in the receptor then inhibits binding of drug at the main receptor

52
Q

What type of antagonism is allosteric antagonism an example of?

A

Non-competitive antagonism

53
Q

What is tolerance in the context of drug administration?

A

Tolerance is the gradual decrease in responsiveness to chronic drug administration.

54
Q

What are some mechanisms that contribute to tolerance? (3)

A
  1. Temporary inactivation of receptors (e.g., phosphorylation).
  2. Sequestration of receptors in the cell (internalization).
  3. Reduced synthesis of new receptors.
55
Q

What happens to responsiveness after the drug is discontinued?

A

Responsiveness returns to basal levels after some time, depending on the drug.

56
Q

What is tachyphylaxis and when does it occur?

A

Tachyphylaxis is a rapid (acute) form of tolerance to a drug.

It can occur with some drugs after the second dose

57
Q

What is supersensitivity?

A

Supersensitivity is an increase in response to a ligand.

58
Q

What usually causes supersensitivity?

A

It is typically due to chronic under-stimulation of a receptor type, leading to an unusually high number of receptors being expressed.

59
Q

When may supersensitivity occur?

A

It may occur when a receptor antagonist has been used chronically and is suddenly withdrawn.

Pharmacology (22 decks)

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