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Animal Medicines > pharmacokinetics + pharmacodynamics > Flashcards

pharmacokinetics + pharmacodynamics Flashcards

1
Q

define pharmacology

(1 mark)

A

science of chemicals (drugs) that interact within the body

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2
Q

define pharmacokinetics

(1 mark)

A

how the drug moves through the body

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3
Q

define pharmacodynamics

(1 mark)

A

what the drug does to the body

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4
Q

what is therapeutic range?

(1 mark)

A

ideal range of drug concentration in body

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5
Q

what happens if drug dose concentration goes above max effective concentration and below minimum?

(2 marks)

A

above max = toxicity
below min = ineffective

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6
Q

what is steady state?

(1 mark)

A

concentration of drug remins stable from dose to dose

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7
Q

how is steady state achieved?

(1 mark)

A

drug is able to be kept within theraputic range over number of doses

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8
Q

what are the stages of pharmacokinetics?

(4 marks)

A

absorption
distribution
metabolism
excretion

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9
Q

what is absorption?

(1 mark)

A

drug travels from site of administration into systemic circulation

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10
Q

how does absorption vary?

(3 marks)

A

drug quality
drug formulation
route of administration

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11
Q

what are the barriers to absorption?

(4 marks)

A

paracellular = squeezes between cells in membrane
transcellular = passes into cell membrane, travels through and passes out other side

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12
Q

how do drugs pass across the membrane?

(3 marks)

A

direct diffusion
facilitated diffusion
active transport

(facilitaed and active use transmembrane carrier proteins)

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13
Q

difference between lipophilic and hydrophillic?

(6 marks)

A

lipophilic = non-polarised + non-ionised, disolves readily in fat
hydrophilic = polarised + ionisied, dissolves readily in water

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14
Q

importance of lipophilic : hydrophilic?

(3 marks)

A

affects the absorption, distribution and elimination of drug

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15
Q

define direct diffusion

(1 mark)

A

passive diffusion following a concentration gradient

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16
Q

what factors does absorption depend on?

(5 marks)

A
  • concentration gradient
  • molecule size
  • lipophilic nature
  • temperature
  • thickness of membrane
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17
Q

what are carrier proteins?

(1 mark)

A

transmembrane proteins - proteins floating within phosphobilipid layer

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18
Q

types of diffusion allowed by carrier proteins?

(2 marks)

A

passive (facilitated)
active

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19
Q

what does passive diffusion not require?

(1 mark)

A

does not require energy

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20
Q

what does active diffusion require?

(1 mark)

A

requires energy (ATP to ADP)

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21
Q

limiting factor of diffusion allowed by carrier proteins?

(1 mark)

A

number of carriers

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22
Q

factors that affect absorption?

(5 marks)

A
  • route of administration
  • method of crossing membranes
  • lipophilic : hydrophilic nature
  • pH of environment
  • tissue perfusion
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23
Q

what are the routes of administration?

(4 marks)

A

IV
IM
SC
PO

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24
Q

what does a plasma concentration over time graph show?

(2 marks)

A

compare peak / max conc that a drug will reach in circulation and
the time over which it is within the bloodstream

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25
Q

how does IV appear on the graph?

(3 marks)

A

administered straight into circulation
100% absorption
plasma conc drops fast because fast absorption into tissues

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26
Q

how does the lipophillic : hydrophilic ratio affect acid and basic drugs?

(2 marks)

A

acid drug = more non-ionisied / lipophilic in acidic environments
basic drug = more ionisied / hydrophilic in acidic environments

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27
Q

how does the pH of the environment affect drugs?

(3 marks)

A

lipophilic : hydrophilic ratio can change depending on pH
affects method / rate of membrane crossing
ion - trapping

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28
Q

what is ion-trapping?

(2 marks)

A

drug becomes trapped due to change in environment
build up of drug in one area

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29
Q

define bioavailability

(1 mark)

A

proportion of drug that reaches circulation when introduced into body

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30
Q

what does AUC work out?

(1 mark)

A

amount of drug absorbed

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31
Q

what does concentration max vs time work out?

(1 mark)

A

how effective drug is

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32
Q

how is distribution of a drug known?

(1 mark)

A

tissue penetration of drug

33
Q

can drugs pass into fat readily?

(1 mark)

A

no = overweight animals have a reduced tissue penetration therefore volume of distribution

34
Q

what is distribution dependant on?

(3 marks)

A

perfusion
capillary wall permeability
protein binding

35
Q

structure of the capillary cell wall?

(1 mark)

A

less permeable meaning only small lipophilic molecules can cross

36
Q

examples of capillary wall structures?

(3 marks)

A

blood brain barrier
placenta
testicles

37
Q

what plasma proteins are produced by the liver?

(2 marks)

A

albumin + globulin

38
Q

what do plasma proteins do?

(2 marks)

A

hold drugs in circulation = inactive and not metabolised / excreted. free : bound ratio.

39
Q

when do you not want a drug to be rapidly absorbed?

(3 marks)

A

slow release tablets and boluses
topical meds - work where applied
local anaesthetic - desensitive nerves in certain areas

40
Q

benefit of drug redistribution?

(1 mark)

A

the effect of drug can be terminated whilst the drug is still in circulation

41
Q

what is biotransformation?

(1 mark)

A

conversion from one chemical enity to another

42
Q

metabolism aids in?

(2 marks)

A

detoxification
elimination

43
Q

how does interference between metabolic pathways affect a drug?

(1 mark)

A

one drug may not be broken down as much and could further impact toxicity in another drug / acumulation of both

44
Q

how are original molecules chemically transformed during phase 1 of metabolic reactions?

(3 marks)

A

oxidation
reduction
hydrolysis

45
Q

what does the molecule become after the transformation process?

(1 mark)

A

metabolite

46
Q

what happens in phase 2?

(3 marks)

A

the metabolite is combined with another chemical substance - conjucation
reduced bioactivity

47
Q

what is excretion?

(1 mark)

A

removal of drug from body

48
Q

what organs are involved in excretion?

(6 marks)

A
  • kidney
  • liver
  • lungs
  • hair
  • milk
  • saliva
49
Q

stages of renal excretion?

(3 marks)

A

glomerular filtration - filtrate squeezed out
passive tubular resorption - some reabsorbed into circulation
active tubular secretion - back into filtrate

50
Q

amount of drug excreted is calculated by?

(1 mark)

A

amount filtered from glomerulus - amount reabsorbed + amount secreted back by active secretion

51
Q

how are drugs excreted by the liver?

(4 marks)

A

drug passively diffuses into hepatocytes (liver cells). once here they can either be excreted directly into the bile, unchanged / metabolised by the liver + then produced into the bile.
once in the bile, the drug is excreted into/via instestines + then out into faeces.

52
Q

what is enterohepatic circulation?

(in terms of hepatic excretion?)

(4 marks)

A

drug is metabolised in liver but binds to glucuronide, which is excreted into bile where is hydrolysed. this allows drug to be reabsorbed back into portal vein + into body. potential for more drug activity.

53
Q

what is half-life?

(1 mark)

A

amount of time taken for half a drug to be removed

54
Q

how many half-lives does it take to reach 95% steady state concentration?

(1 mark)

A

5 half-lives

55
Q

how can the rate of metabolism and excretion be measured?

(1 mark)

A

how long it takes for the drug conc to be reduced by 50% each time.

56
Q

what ways do drugs work within the body?

(3 marks)

A
  • mimic
  • block
  • enhance
57
Q

how do endogenous chemical work compared to agonist and antagonist?

(3 marks)

A

endogenous - specific shape + size. fits + causes reaction.
agonist - similar in shape. binds but not fully - mimic response
antagonist - bind but does not fit perfectly, does not cause response - block

58
Q

what do full and partial agonists do?

(1 mark)

A

full + partial response

59
Q

how do competetive + non-competetice antagonists work?

(8 marks)

A

competitive antagonist binds to same site as normal enzyme - compete for same site - reversible
non-competitive bind to site near receptor. normal receptor. normal receptor change shape - enzyme cannot bind - blocks receptor - irreversible

60
Q

what is drug potency?

(1 mark)

A

how well a drug binds + acts

61
Q

what is drug affinity?

(1 mark)

A

how well drug binds to receptor

62
Q

how does high, medium and low affinity work?

(3 marks)

A

high - strong bond
medium - partially bound - medium strength (some receptor is open and unbound
low - low strength binding as lightly attrached

63
Q

what is EC50?

(2 marks)

A

measure of potency. conc of a drug that induces a response that is halfway between max + min response

64
Q

what is efficiacy?

(1 mark)

A

how effective is the drug at producing a response

65
Q

how is potency determined?

(1 mark)

A

affinity + afficacy

66
Q

what is selectivity?

(1 mark)

A

ability to preferntially bind to one receptor than other

67
Q

what is ideal selectivity?

(1 mark)

A

want drug with high sensitivity to reduce side effects

68
Q

what happens is drug has low selectivity?

(1 mark)

A

drug interacts with lots of different receptors, causing lots of different responses

69
Q

what is specificity?

(1 mark)

A

ability to target the site in which it is required

70
Q

how does binding cause a response?

(4 marks)

A

dependent on type of receptor:
1. ligand-gated ion channel
2. G protein coupled receptor
3. protein kinase receptors
4. intracellular receptor

71
Q

how do ion channels work?

(3 marks)

A

drug binds to receptor
changes shape of protein molecule channel
opens channel to allow it to move to other side of phosphobilipid layer

72
Q

how do local anaesthetics work?

(5 marks)

A

block receptor
nerve depolarisation causes influx of sodium ions into cell
blocks nerve transfer
bind to receptor + block it
channel cannot open - no response

73
Q

how many proteins are in the phosphobilipid layer involved in G-protein coupled receptors?

(1 mark)

A

7

74
Q

how do G-protein coupled receptors work?

(4 marks)

A
  • ligand binds to protein
  • GDP converted into GTP
  • G-proteins released - triggers cascade of events
  • GDP to GTP
75
Q

how do protein kinases work?

(2 marks)

A

catalyse effect of variety of different proteins
either drug molecule binds to receptor / endogenous chemicals

76
Q

how does insulin use protein kinases?

(4 marks)

A
  • insulin = endogenous chemicals
  • bind to tyrosine kinase receptors
  • causes the two molecules to join
  • triggers a cellular cascade in response to insulin binding
77
Q

how do intracellular receptors work?

(3 marks)

A

receptor within cell - inside cytoplasm / nucleus
signalling in cytoplasm / pass through + bind in nucleus
able to attach to DNA to interrupt transcription

78
Q

what does it mean if the body becomes desensitied?

(1 mark)

A

the desired result is no longer achieved due to change in body / prolonged exposure to drug / ligand

79
Q

how can desensation occur?

(5 marks)

A
  • change in receptors - does not achieve same response
  • loss of receptors - go inside cells
  • depletion of mediators - reponse is blocked
  • altered metabolism - quicker = reduction of drug
  • physiological adaptation - body adapt e.g. insulin resistance

Animal Medicines (20 decks)

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