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BDS2 - Pharmacology > pharmacokinetics and pharmacodynamics > Flashcards

pharmacokinetics and pharmacodynamics Flashcards

1
Q

what is pharmacokinetics and pharmacodynamics

A

how drugs affect the body’s physiology

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2
Q

what are the 4 phases of how a drug effects the body

A
  • absorption
  • clinical effect
  • metabolism
  • excretion
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3
Q

what are the 5 routes of administration of a drug

A
  • oral
  • intravenous injections
  • intramuscular injections
  • subcutaneous injections
  • inhalation
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4
Q

what is a misconception of asthma inhalers way of absorption

A

not Inhalation as inhalers have powder in them which do not make it far enough into the alveoli to be absorbed the way - instead absorbed like a cream

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5
Q

what are the advantages and disadvantages of oral administration

A 
advantages
- people don't mind taking pills 
disadvantages 
- slow onset
- variable absorption (may lose some in stomach, gut mucosa not good at absorption)
- gastric acid may destroy drug 
- needs to get through liver
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6
Q

what are the other factors that affect oral drugs absorption

A
  • lipid solubility and ionisation
  • drug formulation
  • gastrointestinal motility
  • interactions with other substances in the gut
  • GIT diseases
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7
Q

how does lipid solubility and ionisation affect absorption of oral drugs

A

will only be absorbed if lipid soluble

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8
Q

how does drug formulation affect absorption of oral drugs

A
  • may have coating which lets different parts of a drug be absorbed at different times
  • coating would need to dissolve first (could take hours or be immediate)
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9
Q

how can GIT diseases affect absorption of oral drugs

A

Crohn’s disease - bowel would be removed so can’t absorb as well/much

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10
Q

what is first pass metabolism

A

all blood from GIT drains into the hepatic portal vein and into the liver which then metabolises drug
- al blood from GIT must pass through liver before entering systemic circulation

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11
Q

how does first pass metabolism work

A
  • drug needs to pass through the liver where it will meet hepatocytes and be metabolised before entering the circulation
  • can lose a lot of the drug through this
  • but knowing this can mean drugs are designed to allow some to be lost in liver but still having enough to work
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12
Q

how can first pass metabolism activate the drug

A
  • can make an active form of an inactive drug (pro-drug)
  • means less needed by oral route
  • e.g. valaciclovir turns into acyclovir
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13
Q

how can first pass metabolism inactivate the drug

A
  • all is lost in liver through metabolism
  • means more is needed by oral route to get the desired effect
  • glyceryl trinitrate
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14
Q

how is drug dosage effected by first pass metabolism

A
  • might need to increase/decrease dose to allows right amount into circulation
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15
Q

what are does based off of

A

a healthy individual

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16
Q

how are drugs from the mouth absorbed

A
  • anything from the mouth doesn’t go through first pass metabolism as doesn’t pass through hepatic portal vein
  • goes dow veins in neck once absorbed and then into systemic circulation
  • different dosage is then needed than oral tablet
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17
Q

what are the advantages of non-oral drugs (injections)

A
  • predictable metabolism
  • no first pass metabolism (goes straight to the circulation- amount given is amount received in blood)
  • works quickly
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18
Q

what are the disadvantages of non-oral drugs

A
  • allergic reaction are more severe as affects the whole body
  • access difficult (patients don’t like giving themselves injections)
  • cost higher (expensive to ensure purity is checked)
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19
Q

what is bioavailability

A

how much does the drug work

- proportion of an ingested drug that is available for clinical affect

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20
Q

what is intravenous bioavailability

A

100%

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21
Q

why is oral drugs bioavailability less than intravenous

A
  • due to first pass metabolism

- lots of variables affect it - can change daily in the same person

22
Q

how is bioavailability modified

A
  • dosage form
  • destruction in the gut
  • poor absorption
  • first pass metabolism
23
Q

what are clinical trials used for

A

guarantee does and what happens/effects

24
Q

why is amoxicillin used more instead of penicillin

A

because it is more predictable in its bioavailability

25
Q

how are drugs distributed throughout the body

A

in the blood

26
Q

what does the vascularisation have to do with drug distribution

A

the more vascularised a part of the body is, the more drug will go to that part of the body

27
Q

what is “volume of distribution”

A

the more blood in the tissue, the more drug

28
Q

what are the different ‘compartments’ of the body the drug will go through

A

vascular, tissues, CNS

29
Q

how does lipid binding affect drug distribution

A

drugs are slowly released from accumulation

30
Q

what role does plasma proteins have in drug distribution

A
  • the bound drug is inactive (can act as a reservoir if too much in the body to handle)
  • drug interactions are possible by competitive binding which causes differences in how drugs work (warfarin and aspirin for example)
31
Q

what is drug metabolism

A

preparing the drug for elimination from the body

32
Q

what are phase 1 metabolism reactions

A
  • carry out little reaction to the molecule
  • change molecule conformation
  • oxidation, reduction and hydrolysis
33
Q

what are phase 2 metabolism reactions

A
  • add drug to another molecule to be excreted

- conjugation (glucoronidation, sulphating, methylation, acetylation, glutathione - helps excretion)

34
Q

what fruit can activate the P45O mono-oxygenate system

A

grapefruit

35
Q

how can drug levels in the body be tested

A

by any bodily fluid excreted

  • why the police us a breathalyser (amount in breath is proportional to amount in the body)
  • renal = urine
  • liver = bile
  • lungs = exhaled gas
  • also get sweat and saliva
36
Q

what disorders can affect drug excretion

A

renal disease or liver disease

37
Q

how does renal disease affect drug excretion

A
  • chronic renal failure

- need less dose as it takes longer to excrete

38
Q

how does liver disease affect drug excretion

A
  • liver failure

- doses must be reduced

39
Q

how is planning drug use based

A

on ‘body compartments’

40
Q

what is the single compartment model

A

drug behaves as if it is evenly distributed throughout eh body

41
Q

what is the 2 compartment model

A

drug behaves as if it is in equilibrium with different tissues in the body
- goes to tissue with large blood flow first then distributes throughout the rest of the body

42
Q

what is the plasma half life

A

the time it takes for half of the drug to leave the system

43
Q

what is the 1st order kinetics for drug clearance

A
  • drug elimination or absorption is by passive diffusion only
  • removed at rate proportional to concentration of drug
  • higher concentration = faster clearance
  • can predict from half life
  • logarithmic graph of elimination is a straight line
44
Q

what order of kinetics do most drugs undergo

A

first order

45
Q

what is 0 order kinetics

A
  • only remove a certain amount an hour
  • drug elimination is an active process and can be saturated by a high drug concentration
  • can have too much for an enzyme system to remove at time (causes different system to kick in which can leaf to liver failure )
  • have constant rate of drug elimination (predictable)
46
Q

what kind of kinetics does alcohol undergo

A

0 order kinetics

- enzymes become over saturated which is why it takes so long to leave system

47
Q

what order of kinetics is paracetamol

A

0 order

48
Q

what is drug accumulation

A

plasma concentration will build up if repeated doses of a drug are given
- drug administration should balance drug clearance (changes per person - doses differ)

49
Q

how is dosing determined

A

by drugs ‘therapeutic index’

50
Q

what happens with too frequent dosing

A

cause raised plasma levels that may be toxic

51
Q

what happens with infrequent dosing

A

results in sub-therapeutic plasma levels and no clinical effect

BDS2 - Pharmacology (3 decks)

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