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BDS2 BAMS Pharmacology > Pharmacokinetics and pharmacodynamics > Flashcards

Pharmacokinetics and pharmacodynamics Flashcards

1
Q

what is pharmacodynamics

A

branch of pharmacology concerned with the effects of drugs and the mechanism of their action

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2
Q

what is pharmacokinetics

A

branch of pharmacology concerned with the movement of the drug within the body

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3
Q

what are the 4 phases to drugs

A

Absorption
Clinical effect
Metabolism
Excretion

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4
Q

what are the different ways to administer drugs

A 
oral
intravenous
intramuscular 
subcutaneous
inhalation
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5
Q

what are the advantages to oral administration

A

socially acceptable

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6
Q

what are the disadvantages to oral administration

A

slow onset
variable absorption
gastric acid may destroy drug

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7
Q

what do we mean when we say there is variable absorption of oral administered drugs

A

we do not know how much of the drug is going to be absorbed as there are so many variables that affect the absorption

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8
Q

what are other factors that affect oral absorption of drugs

A 
lipid solubility and ionisation
drug formulation
gastrointestinal motility
interactions with other substances
gi tract disease
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9
Q

how does lipid solubility and ionization affect the absorption of an orally administered drug

A

we can only absorb it if it is lipid soluble as because the cell membrane is lipid, lipid soluble drugs diffuse most rapidly. We can only hold the drug in the gut if it is not in ionic suspension

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10
Q

how does GI tract disease affect the absorption of an orally administered drug

A

if the gut is static for a while you will not move solutions through so you cannot move the drug to where it needs to be absorbed

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11
Q

what is first pass metabolism

A

blood of the gut is drained by hepatic portal vein and takes it to the liver

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12
Q

what happens in first pass metabolism

A

drug goes through hepatocytes and must be metabolized before going through circulation meaning that we will lose some of the drug in the liver

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13
Q

why do drugs that are absorbed through the mouth or top of the oesophagus have a quicker effect

A

do not go through HPV

bypass first pass metabolism

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14
Q

what veins do not drain into the hepatic portal veins

A

sublingual and rectal

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15
Q

when the drug goes through the liver it can have 1 of 2 effects, what are they

A

inactivate drug

activate drug

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16
Q

what does inactivation of drug by the liver mean

A

more is needed by oral route to get the desired clinical effect

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17
Q

what does activation of the drug by liver mean

A

makes an active form from an inactive drug

less is needed by oral route

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18
Q

what is an example of a drug that the liver inactivates during FPM

A

glyceryl trinitrate

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19
Q

what is an example of a drug that the liver activates during FPM

A

aciclovir

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20
Q

why is it important to know if a patient has abnormal liver function in respect to first pass metabolism

A

If the patient has abnormal liver function then there is a problem as the patient may not lose as much of the drug to first pass metabolism

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21
Q

when is abnormal liver function most common

A
  • Extremes of life
  • Liver disease
  • Drug interactions changing drug metabolism
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22
Q

what are the advantages to non-oral administration

A
  • It has predictable plasma levels
  • No first pass metabolism – injections bypass first pass metabolism and it means you know the drug is where it needs to be and you know it is working know and you know its dose
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23
Q

what are the disadvantages to non-oral administration

A

allergic reactions are more severe
access difficulity
cost is higher

24
Q

what is bioavailability

A

Bioavailability is the proportion of an ingested drug that is available for clinical effect

25
Q

why can the bioavailability of oral drugs be low

A

variables may change the bioavailability of medicine and it changes day to day depending on what is happening inside the body

26
Q

what is bioavailability modified by

A
  • Dosage form
  • Destruction in the gut
  • Poor absorption
  • First pass metabolism
27
Q

what is volume of distribution

A

Defined as the arrangement or rate of incidence of a drug in the body in relation to the measured plasma concentration

Depends on blood flow to the different compartments and the ease of drugs going from the blood to the circulation

28
Q

describe how we carry more drugs in the circulation than we can dissolve

A

can bind to lipids

can bind to plasma proteins

29
Q

describe how drugs can bind to lipids

A

they are bound to lipids in the plasma and there is a slow release from accumulation

30
Q

describe how drugs bind to plasma proteins

A

o The bound drug is inactive
o This can act as a reservoir – the drug in the plasma will move into the tissues and then the drug in the plasma proteins will move into the plasma creating a reservoir

31
Q

how can drug binding to plasma proteins be effected by competitive binding

A

different things bind to the same protein and this can change the way that drugs work

32
Q

describe drug metabolism

A

prepare the drug for elimination from the body

33
Q

describe phase 1 of drug metabolism

A

inactivate the medicine
oxidation
reduction
hydrolysis

34
Q

describe phase 2 of drug metabolism

A 
get drug out of the body
glucoronidation
sulphation
methylation
acetylation
glutathione
35
Q

what is p450 monoxygenase system

A

variety of changes happen to the drug for excretion

the metabolism process can be interfered

36
Q

what are the different ways the drugs can be excreted

A 
Renal – urine
Liver – bile
Lungs – exhale gas 
sweat
saliva
37
Q

what is renal excretion

A

The kidney has a complex mechanism where it modifies the urine – the urine solution in the glomerulus mimics the amount in plasma. It changes in tubules as they add more drug or leave the drug

38
Q

why is renal disease significant

A

impacts the ability to get rid of the drug and the drug can build up in circulation

39
Q

what can changing pH of urine do

A

enhance excretion of acidic compounds and can help get rid of excess drug

40
Q

what are disorders of excretion

A 
Renal disease (chronic renal failure) 
Liver disease (liver failure) 
means that drug doses must be reduced
41
Q

what is planning drug use based on

A

idea of body compartments

42
Q

what are the 2 compartment models

A

single compartment model

two compartment model

43
Q

what is the single compartment mode

A

the drug behaves as if it is evenly distributed throughout the body

44
Q

what is the two compartment model

A

drug behaves as if it is in equilibrium with different tissues in the body

45
Q

what is the plasma half life of a drug

A

Period of time required for the concentration of a drug in the body to be reduced by one half.
We usually consider the half life of a drug in relation to the amount of drug in plasma – its half life depends on its clearance

46
Q

what are the two ways drugs can be cleared

A

first order kinetics

zero order kinetics

47
Q

describe first order kinetics

A

Drug elimination or absorption is by passive diffusion only – the drug goes into circulation and is removed from the body at a rate proportional to the concentration of a drug

48
Q

what is the logarithmic graph of elimination by first order kinetics like

A

straight line

half life is constant

49
Q

what is zero order kinetics

A
  • Drug elimination is an active process and can be saturated by high concentrations
  • You can only remove a certain amount of a drug per hour
50
Q

what is the graph of first order kinetics like

A

linear

51
Q

what drugs use zero order kinetics

A

alcohol

paracetamol

52
Q

what is drug accumulation

A

how the plasma concentration builds if repeated doses of a drug are given

53
Q

what happens if the dosing schedule is too frequent

A

result in plasma levels that may be toxic

depends on the drug therapeutic index

54
Q

what happens if the dosing schedule is too infrequent

A

result in sub-therapeutic plasma levels and no clinical effect

55
Q

What do you need to know to calculate the dosing schedule

A

HALF LIFE, how its eliminated and how it accumulates

BDS2 BAMS Pharmacology (4 decks)

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