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PHAR > introduction to pharmacology-pharmacokinetics > Flashcards

introduction to pharmacology-pharmacokinetics Flashcards

1
Q

what is absorption?

A

passage of a drug from the site of administration into the plasma

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2
Q

what is bioavailability?

A

fraction of the initial dose that gains access to the systemic circulaton

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3
Q

what determines the absorption and bioavailability of a drug?

A

the site of administration?

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4
Q

give examples of different site administrations

A

intra-venous
inhalation
dermal
sub-lingual

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5
Q

in how many ways can the drug move around the bodies? what are they?

A

2 ways:

  • bulk flow transfer=in the bloodstream
  • diffusional transfer=molecule by molecule across short distances
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6
Q

for all routes EXCEPT the intravenous route, the drug needs to cross at least 1 lipid membrane. what are the 4 different mechanisms by which a drug can cross a lipid membrane?

A

pinocytosis
diffusion through lipid
diffusion through aqueous pores (VERY RARE)
carrier proteins

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7
Q

what does the diffusion through lipid depend on?

A

lipid solubility

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8
Q

what is the pathway for oral administration?

A

small intestine microvilli–>blood vessels to enter blood–>blood vessels to access relevant tissue

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9
Q

what is the pathway for inhalation?

A

alveoli/bronchi–>blood vessels to enter blood–>blood vessels to access relevant tissue

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10
Q

what is the pathway for intra-nasal?

A

mucous membrane of nasal sinus–>blood vessels to enter blood–>blood vessel to access relevant tissue

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11
Q

do drugs exist in ionised or non ionised states?

A

both

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12
Q

charged molecule that are more polar are less or more lipid soluble?

A

LESS

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13
Q

is pH a huge determinant of absorption of drugs across lipid?

A

yes

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14
Q

how is the ratio of ionised to unionised drug determined?

A

by the dissociation constant pKa and the pH in a particular part of the body

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15
Q

does the pKa of a drug change?

A

no

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16
Q

what is the pH partition hypothesis?

A

the proportion of drug in any body component is dependent on pH

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17
Q

what does the carrier transport system do?

A

present to regulate the entrance and exit of physiologically important molecules across lipid membranes
drugs that resembles endogenous molecules may also interact with this carrier system
less lipid soluble drugs can have access to tissues via this route

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18
Q

where can we find the most important carrier systems relating to drug action?

A
  • renal tube
  • biliary tract
  • blood brain barrier
  • gastrointestinal tract
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19
Q

what are the major advantages of a local effect of a drug?

A

the drug is delivered directly in the intended site

a high lock concentration can be administered without worrying about systemic effects

20
Q

what factors influence tissue distribution?

A
  • regional blood flow
  • plasma protein binding
  • capillary permeability
  • tissue localisation
21
Q

what is albumin?

A

most important blood plasma protein

22
Q

what factors influence the amount of drug bound?

A
  • free drug concentration
  • affinity for the protein binding site
  • plasma protein concentration
23
Q

is plasma protein ever saturated with drugs?

A

no NEVER

24
Q

can drugs diffuse across the membrane if bound to a plasma protein?

A

no it has to dissociate first

25
Q

what drugs can go across endothelial cells?

A

very lipid soluble drugs

26
Q

what is the most difficult tissue in the body to get drugs to?

A

brain

27
Q

how are the endothelial cells in the liver?

A

discontinuous

28
Q

what is the liver?

A

key metabolic tissues in the body and deals with metabolism of a huge variety of chemicals including the majority of drugs

29
Q

what is the glomerulus of the kidney?

A

key tissue involved in excretion of chemicals including a large number of drugs

30
Q

what is the oil/water partition coefficient?

A

how well a drug dissolves in fat vs how well it dissolves in water

31
Q

should drugs be lipid soluble to be secreted?

A

no

32
Q

do we want the drug to be lipid soluble? why?

A

yes for it to be effective

33
Q

how does the body make a drug less soluble?

A

metabolism

34
Q

what is metabolism?

A

conversion of drugs to metabolites

35
Q

what is the major metabolic tissue?

A

liver

36
Q

what enzyme in the liver is responsible for metabolism?

A

cytochrome p450 enzyme

37
Q

what are the biochemical reactions that are involved in drug metabolism?

A

phase 1: introduction of a reactive grp to a drug

phase 2: addition of a conjugate to the reactive grp

38
Q

what are pro-drugs?

A

drugs that have no activity of its own but after phase 1 of metabolism, produce a pharmacologically active drug metabolites
so metabolism is REQUIRED for the pharmacological effect

39
Q

what happens to the drug at the end of phase 2?

A

it becomes much less lipid soluble which facilitate excretion in the urine or bile

40
Q

what are the enzymes for phase 1 and 2 of metabolism?

A

phase 1: cytochrome p450 enzyme

phase 2: transferases (to transfer the substituent grp onto the base 1 metabolite)

41
Q

what is first pass hepatic metabolism? what is the problem?

A

when drugs, especially orally administrated drugs, first pass through the liver before they reach the systemic circulation
at this point the drug will be heavily metabolised which will result in little active drug available to reach the systemic circulation

42
Q

what are the 3 major routes of drug excretion?

A
  • glomerular filtration
  • active tubular secretion
  • passive diffusion across tubular epithelium
43
Q

what is the best way of excretion to effectively remove phase 2 glucuronide metabolites?

A

biliary excretion

44
Q

what is enterohepatic recycling?

A

process that can significantly prolong drug effect and increase the length of time it takes to eliminate the drug

45
Q

what is half-life?

A

time taken for 50% of the drug to be eliminated from the body

PHAR (5 decks)

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