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Y1 - ICPP > Lecture 19 - Pharmacokinetics I > Flashcards

Lecture 19 - Pharmacokinetics I Flashcards

1
Q

What type of signalling molecule is a drug?
Exogenous or endogenous?

A

Exogenous signalling molecule

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2
Q

What are the 4 basics steps to a drugs lifecycle in the body?

A

Absorption
Distribution (around body)
Metabolism (producing its effect)
Excretion

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3
Q

What are the 2 stages which involve the drug going in?

A

Absorption
Distribution

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4
Q

What are the 2 stages which involve the drug going out?

A

Metabolism
Excretion

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5
Q

What mneumonic can be used to remember the 4 stages of the lifecycle of a drug?

A

ADME

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6
Q

What are the 2 classes of drug administration?

A

Enteral
Paraenteral

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7
Q

What is enteral drug administration?

A

When the drug is directly administered into the GI tract

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8
Q

What are the 3 methods of enteral drug administration?

A

Oral
Sublingual
Rectal

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9
Q

What is paraenteral drug administration?

A

Delivery via all other routes that are not the GI tract

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10
Q

What are some examples of paraenteral drug administration?

A

Intravenous
Subcutaneous
Intramuscular
Transdermal
Inhalation
Intranasal

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11
Q

What is the pneumonic to remember some drug administration routes?

A

Oi It is Sir

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12
Q

What does the mneumonic for remembering drug administration routes stand for?

A

Oi It Is Sir

Oral
Intravenous

Intramuscular
Transdermal

Intra -nasal
Subcutaneous

Sublingual
Inhalation
Rectal

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13
Q

What is the main site of drug absorption in the body?

A

Small intestine

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14
Q

Why is the stomach not an ideal target for drugs?

A

Has a thick mucus which acts as a barrier to drug absorption

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15
Q

How does the pH of the small intestine compare to the stomach?

A

Small intestine is much more weakly acidic (pH 6-7)

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16
Q

How is surface are of the small intestine for absorption maximised?

A

Villi
Microvilli on villi

Plica circularis (numerous folds of mucous membrane)

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17
Q

What are the 3 methods by which drugs can be absorbed into the body?

A

Passive diffusion
Facilitated diffusion
Secondary active transport

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18
Q

What type of drugs are absorbed by passive diffusion?

A

Lipophilic drugs like steroids
Weak acids and weak bases

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19
Q

What type of dissocation does a weak acid or base do?

A

Partial dissociation (not full)

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20
Q

What is an example of an anti-epileptic drug (weak acid)?

A

Valproate

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21
Q

What is the typical transit time of drug absorption in the small intestine?

A

Between 3-5 hrs

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22
Q

Will a drug be able to pass through a membrane if it’s charged or uncharged?

A

Pass through more readily when uncharged

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23
Q

Will a weakly acid drug pass through a membrane more easily if a higher proportion of it is Protonated or un-Protonated?

A

More Protonated = more easily absorbed due to it not being charged

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24
Q

What process must molecules with a net charge undergo in order too be absorbed across GI epithelia?

A

Facilitied diffusion (Solute Carrier (SLC) transport)

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25
Q

Where are SLC 22 family like OATs and OCTss highly expressed?

A

GI epithelia
Hepatic epithelia
Renal epithelia

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26
Q

What is the general process of secondary active SCL transport across on OAT or OCT?

A

Transport driven by pre-existing electrochemical gradient drives against electrochemical gradient across GI epithelial membrane

27
Q

What are some examples of negatively charged drugs that cross the GI epithelia via SLC transport?

A

Prozac/Fluoxetine
Penicillins

28
Q

What is Fluoxetine/Prozac co-transported with?
What type of drug is it?

A

Co-transported with Na+ (drug is -Ve)

Is an SSRI antidepressant

29
Q

What does a SSRI antidepressant stand for?

A

Selective serotonin re up take inhibitor

30
Q

What are penicillins co-transported with via secondary active SLC transport?

A

H+

31
Q

What Physicochemical factors affect drug absorption?

A

GI length or surface
Drug lipophilicty
Density of SLC 22 OAT/OCT expression in GI

32
Q

What GI Physiological factors affect drug absorption?

A

Blood flow (higher post meal)
GI motility (slow post meal)
Food/pH

33
Q

What is first pass metabolism?

A

When the drugs begin to get metabolised/denatured before it gets absorbed

34
Q

Which parts of the body does first metabolism occur?

A

GI (gut lumen and gut wall)
Liver

35
Q

What are the different types of Phase Enzymes?

A

Phase I Enzymes
Phase II Enzymes

36
Q

What is an example of Phase I Enzymes?

A

Cytochrome P450s

37
Q

What is an example of Phase II enzymes?

A

Conjugating enzymes

38
Q

Where are the majority of Phase I and II enzymes?

A

Liver

39
Q

How does first pass metabolism affect therapeutic potential of a drug?

A

The more that a drug gets metabolise, the less of the drug that will actually get absorbed

40
Q

What is Bioavailability?

A

The fraction of a defined dosewhich reaches its way into a specific body compartment

41
Q

What is the most common reference body compartment for bioavailability?

A

CVS circulation

42
Q

What is meant by the IV bolus = 100% for CVS compartment bioavailability?

A

No physical/metabolic barriers to overcome

43
Q

What is intravenous bioavailability commonly compared with?

A

Oral bioavailability
(O)/(IV)

44
Q

What is the first stage of how drugs journey through the body?

A

Bulk flow
Diffusion

45
Q

What is bulk flow of a drug?

A

Large distance travelled by the drug via the arteries to the capillaries

46
Q

What are some potential barriers to diffusion?

A

Certain interactions of substances with the drug may prevent diffusion
Area may not be permeable

47
Q

What are the 3 different types of capillaries with varying permeability?

A

Continous
Fenestrated
Sinusoid

48
Q

What endogenous transporters do capillary membranes express?

A

OATs
OCTs

49
Q

Where are continuous capillaries typically found?

A

CNS (Blood Brain Barrier))
PNS
Cochlea
Muscle
Skin
Fat

50
Q

Where are fenestrated capillaries typically found?

A

Intestine
Endocrine/exocrine
Kidney Glomeruli

51
Q

Where are sinusoid capillaries typically found?

A

Liver
Bone marrow
Spleen
Lymph

52
Q

Compare lipophilic and hydrophiliic drugs ability to cross membrane barriers:

A

Lipophilic = freely move across membrane barriers

Hydrophilic = can journey across membrane barriers dependant on factors for Absorption:
Capillary permeability
Drug pKa + local pH
Presents of OATs/OCTs

53
Q

What is an example a plasma protein which a drug may bind to?

A

Albumin

54
Q

Can a drug bind to its target site when bound to a tissue protein?

A

No
Drug must be dissociated from the plasma/tissue protein

55
Q

How may multiple drugs affect there binding to tissue proteins?

A

2 drugs might bind to the same site on albumin so there may be competition for binding site affecting free plasma concentration of the drug

56
Q

What are the 3 main body fluid compartments in the body?

A

Plasma
Extracellular water
Total body water

57
Q

How much total body water in the average 70kg male?

A

42 litres

58
Q

How does a drug move from between the 3 body fluid compartments?

A

Plasma —> Interstitial fluid —> Intracellular

59
Q

When increasing penetration by a drug into interstitial and intracellular fluid compartments, how does this affect:

Plasma drug concentration?
Vd?

A

Decreasing Plasma Drug Concentration
Increasing Vd

60
Q

What is Vd?

A

Apparent Volume of Distribution

It summarises the movement of drug from plasma —> interstitial —> intracellular compartment

It is referenced to plasma concentration

61
Q

What does a small Vd value for a drug indicate?

A

Less penetration of Interstitial/Intracellular fluid compartment

62
Q

What does a Larger Vd value indicate?

A

Greater penetration of interstitial/intracellular fluid compartment

63
Q

What are the units for Apparent Volume of Distribution (Vd)?

A

Litres (assuming the standard 70kg male)

64
Q

What can affect Vd?

A

Changes in regional blood flow
Hypoalbunimea - affecting protein binding
Drug interactions
Pregnancy
Cancer patients
Anaesthetics

Y1 - ICPP (23 decks)

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