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ASC306 > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

Explain Pharmacodynamics

A
  • mechanisms of durg action
  • drug receptors
  • drug properties
  • variation in drug response
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2
Q

Explain Drug action

A

Drug molecules bind to cells

resulting in a drug receptor combination

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3
Q

Explain Drug Effect

A

Biochemical and physiological changes as a consequence of drug action

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4
Q

What are the three sites of drug action?

A
  • Extracellular receptors
  • Cell membrane receptors
  • intracellular receptors
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5
Q

Wat are some of the Drug receptors?

A
  • Regulatory proteins
  • enzymes
  • transport proteins
  • structual proteins
  • mutisubunit ion channels
  • G-protein coupled receptors
  • Protein Kinases
  • transcrption factors
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6
Q

Intracellular receptors are important for..?

A

hormone binding

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7
Q

which receptors are important or cytokine and peptide binding?

A

ligand-activated transmembrane enzymes

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8
Q

the model that reflects the actions of receptors best is?

A

the lock and key model as receptors are highly specific

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9
Q

explain E, Emax and E50

A

E: effect observed at concentraion

Emax: MAX response of drug, limited to availble receptors

EC50: conc. of drug that results in 50% of MAX effect

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10
Q

explain,

C, Bmax, and KD

A

C: conc. of free unbound drug

Bmax: total conc. of receptor sites

KD: conc. of free durg at which half-max binding is observed (Drugs infinity for receptor)

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11
Q

the dose response curve

A

answers Q’s about drug efficency, toxicity and potency

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12
Q

response is proportional to the number to receptors occupied therefore

A

concentration to reach max reponse will decrease as he number of receptors increases.

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13
Q
  1. which is the most potent drug?
  2. which drug has the lowest max efficency?
A
  1. Drug X
  2. Drug Y
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14
Q

comparision of the curves with a known full agonist tells what about the antagonist?

A

about its potency

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15
Q

Explain a full antagonist

A

ligand-receptor interaction results in no response at all

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16
Q

What is A B and C

A

A: Full agonist (results in a full response)

B: Partial Antagonist (results in a partial response)

C: Antagonist

17
Q

What is a mixed agonist?

A

occurs when partial agonists compete with a full agonist to reduce Emax.

18
Q

Explain a competitive antagonist

A
  • the antagonist will bind to the receptor but no response
  • is reversible
  • will shift the dose curve to the right
  • higher concentrations the drug are required to achieve the max efficency (ie potency decreases)
    • can be overcome by adding more drug
  • most antagonists are competitive
19
Q

explain the antagonist causing this response

A

a non competitve antagonist

  • Emax will be less than for antagonist alone
  • formation of non-reversable bonds
  • curve becomes more narrow due to a decrease in receptors
  • few antagonists are non-competitive
20
Q

what is

  1. an agonist
  2. an antagonist
A
  1. agonist –> mimics/ stimulates
  2. antagonist –> blocks (eg propanol beta-blocker, prevents adrenaline and decreases heart rate)
21
Q

explain Drug tolerance

A

response is proportional to the number of receptors occupied

22
Q

Explain Down-regulation and give an example

A

down regulation of number of receptors availble to down regulate response

e.g. in response to increased adrenaline

23
Q

explain up regulation and how it relates to the need for some animals to be weaned off drugs

A
  • involves the upregulation of receptors to return to homeostasis
    • when HR is too low the receptors will be upregulated in response.
  • also occurs when antagonists bind to receptors and more receptors are needed for normal function
  • weaning off drugs –>
    • the receptors will be upreguated in response to increased antagonists and once off drug (ie loss of antagonist) too many recptors are present causeing in the example of propanol cardiac arrest. therefore drugs must be weaned off.
24
Q

Explain tachyphylaxis and give an example

A
  • occurs when the body has a diminished response via an inhibitory feedback loop from:
    • repeated administration
    • Diminished responses to the same dose
  • degree of tachyphylaxis is proportional to the degree of stimulus
  • example:
    • nicotine
    • dobutamine
    • metoclopramide
    • nitroglycerine
25
Q

Explain the concept of tolerance and give an example

A
  • shorter pharmacological response
  • OR: change in the drug receptor function
  • example:
    • morphine
    • heroin
  • more drug is needed to achieve Emax
26
Q

True or False

Effect drug plasma concentrations are usually not preserved across the species

A

FALSE

they are usually preserved e.g. phenobartitone at 15 microgram/ml will have anticonvulsant activity in a rat or ridgeback

27
Q

True or False

ADME exhibits interspecies variation and due to this CL, Vd and T1/2 may vary

A

TRUE

28
Q

what are the phase II metabolism deficiencies in the feline, canine, porcine and humans.

A
  • feline: SLOW glucuronidation
  • canine: acetylation absent
  • porcine: slow sulfation
  • humans: % of slow acetylators
29
Q

True of False:

Drugs are less likely to exhibit pharmacokinetic variation if they are metabolised by the liver.

A

FALSE

they are more likely

30
Q

True or False:

Drugs that are elminated unchanged by the kidneys exhibit less interspecies variation.

A

TRUE

31
Q

Phenylbutazone has a low clearance in cattle and humans

this means…

A

it stays in the system for too long and is therefore toxic to cattle and humans.

32
Q

True or False:

Drug half lives are generally shorter in ruminants and horses compared with dogs and cats

A

TRUE

33
Q

True of False

generally drug half lives are shorter in humans compared with domestic animals

A

FALSE

drug half lives are considerably longer in humans compared with domestic animals

34
Q

Give an example of interspecies variability

A
  • ruminants and xylazine (alpha 2 agonists)
    • 1/10th doses more sensitive to receptors
    • brahams and goats are even more sensitive
    • not the case for other drugs in this class
  • collies and some reptiles with ivermectin
    • not good at keeping them out of the brain
  • felines and NSAIDs
    • poor glucuronidators
    • clinical significance… minor –> fatal
35
Q
A

ASC306 (13 decks)

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