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20003 > pharmacokinetics > Flashcards

pharmacokinetics Flashcards

1
Q

what is pharmacokinetics

A

processes that affect the bioavailability of a drug to its target

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2
Q

what are the areas that affect the pharmacokinetics

A

Absorptions from site of administration
Distribution
Metabolism
Excretion

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3
Q

what does bioavailability mean

A

the fraction of administered dose that reaches the system

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4
Q

what are different enteral routes for administration

A
  • oral
  • sublingual
  • rectal
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5
Q

what is first pass metabolism

A

drugs passing through the GIT pass through the liver and are partially metabolized reducing drug for distribution

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6
Q

what are the parenteral routes of administration

A
  • IM
  • subcutaneous
  • IV
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7
Q

what are additional routes of administration

A
  • epithelial surfaces
  • transdermal
  • inhalation
  • IO
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8
Q

what effects the rate of absorption

A
  • route of administration
  • environment where the drug is absorbed
  • physiochemical nature of the drug
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9
Q

how does blood flow affect absorption

A

increased blood flow increases absorption causing immediate effect

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10
Q

how does food affect absorption

A
  • after a meal slower absorption from small intestine delay
  • increase splanchnic blood flow increase rate of absorption
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11
Q

how does pH affect absorption - acidic

A

acidic drug going into an acidic area needs to be unionized as this makes them lipid soluble to be absorbed

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12
Q

how to ph affect absorption - weak base drug in acidic

A

weak base drugs in acidic area for salts (ionised which cant bas through the bilayer - absorption needed in intestine

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13
Q

how does drug solubility affect absorption

A

different drug forms are absorbed faster eg aqueous is faster and more completely than tablet or suspension

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14
Q

what is the affect of chemical instability in absorption

A

different drugs are unstable in different ph concentrations

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15
Q

what is distribution

A

delivery of drugs from the systemic circulation to extracellular fluids/ tissue

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16
Q

what is the blood brain barrier

A

tightly joined endothelial cells that stop drug access to the brain

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17
Q

how do drugs become pharmacologically active

A
  • drugs are bound to plasma proteins others are unbound
  • unbound drugs are pharmacologically active as they can access different organs and leave the blood stream
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18
Q

what occurs at drug competition for protein binding

A
  • higher affinity for plasma are administered displacing other drugs attached
  • what is attached becomes pharmacologically active
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19
Q

drug distribution calculation

A

Vd = Q/Cp
Q = amount of drug
Cp = plasma concentration

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20
Q

what does the drug distribution show

A
  • small Cp, Vd is high so drugs widely distributed
  • high Cp, Vd is small so drug no widely distributed
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21
Q

what is phase 1 metabolism

A

conversion of lipophilic molecules into more polar molecules by the cytochrome system

22
Q

what is phase II metabolism

A

conjugation of the drug of it metabolites with glucuronyl sulphate, methyl, acetyl moiety

23
Q

what is the purpose of phase I and II metabolism

A

lipophilic drugs becoming more polar and are conjugated with other metabolised to become more water soluble for excretion

24
Q

what happens to active drugs in metabolism

A

entering phase I and II they become less active

25
Q

what happens to non active drugs in metabolism

A

entering phase I and II they become more active

26
Q

what physiological factors affect microsomal enzyme activity

A
  • age
  • sex
  • hormones
  • nutrition
27
Q

how does nutrition affect microsomal enzyme activity

A

some foods act as an enzyme inhibitor so the drug accumulates leading to toxic effects

28
Q

how do environmental factors affect microsomal enzyme activity

A
  • stress
  • foreign compound
  • drugs
29
Q

how do enzyme inhibitors affect microsomal enzyme activity

A
  • competition for CYP enzyme active site
  • drug with a greater affinity inhibits its own metabolism and decrease metabolism of unrelated drugs
30
Q

how do enzyme inducers affect microsomal enzyme activity

A
  • enhance enzyme activity
  • accelerating metabolism and activity of enzyme and drug
  • causing therapeutic failure
31
Q

what is non-microsomal oxidations

A

metabolism of enzymes outside of the liver

32
Q

what causes the oxidation of noradrenaline

A

monoamine oxidase - forming noradrenaline aldehyde

33
Q

what is excretion

A

process of drug removal from internal to external environment

34
Q

what does the kidney excrete

A

water and soluble drugs as the kidney also absorbs water

35
Q

how does kidney failure affect excretion

A

drug accumulation as less processing

36
Q

what is an ionized drug

A

a drug composed of ions

37
Q

what is an unionized drug

A

a drug with no charge

38
Q

how are ionized drugs excreted

A

they are unable to pass through the phospholipid bilayer so are excreted

39
Q

how are unionized drugs excreted

A

they are reabsorbed by passive diffusion back into the body

40
Q

where would a drug be ionised

A

a weak base areas with an acidic drug

41
Q

where would a drug be unionised

A

a weak base area with a weak drug

42
Q

what are extra renal routes of excretion

A
  • lungs
  • milk
  • biliary system and faecal route
  • skin
  • hair
  • tears
  • saliva
  • sweat
43
Q

what is medication half life

A

the time required for a drug to be eliminated by half of its blood concentration level

44
Q

what affects the medication half life

A

metabolization

45
Q

when is a steady state reached in half life

A

around 5 times the half life

46
Q

what is clearance

A

the volume of plasma apparently cleared of drug in unit time

47
Q

what is the cause of slow clearance

A

these drug will accumulate so needed a less frequent lower dose

48
Q

what is the cause of a high clearance drug

A

removed faster so need a higher dose with a therapeutic dose given

49
Q

what is ion trapping

A

trapping the drug in the form of ions making it more soluble to be easily excreted

50
Q

how does urine ph affect excretion

A

a weak acid or base can be more ionised in urine so easily excretion

51
Q

when does ion trapping occur

A

intoxication to increase renal excretion of certain drugs and toxins

20003 (17 decks)

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