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4th yr- CMS- Pharmacology and drugs > DRUG ABSORPTION, DISTRIBUTION, > Flashcards

DRUG ABSORPTION, DISTRIBUTION, Flashcards

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Introductory Sommelier Exam (CMS) flashcards
1
Q

Talk through the journey of a drug through the body

A
  1. Absorption
  2. Targets Site of action
  3. Metabolism
  4. Excretion
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2
Q

How do drugs enter the body

A

They have to cross barriers to be able to enter eg skin, gut walls

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3
Q

What happens once a drug is absorbed into the body

A

The blood distributes the drug to the sites of action across more barriers

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4
Q

Where are drugs metabolised and excreted

A

Kidney and or liver

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5
Q

What does ADME stand fro

A

Absorption
Distribution
Metabolism
Excretion

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6
Q

For which drugs is the acronym ADME relevant for

A

ALL DRUGS can be used to manipulate the treatment to make ti more effective

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7
Q

How can drugs be absorbed into the body

A
  1. Enteral

2. Parenteral

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8
Q

What is enteral

A

In or through the digestive system

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9
Q

Give some way s a drug can be absorbed enterally

A
  1. Oral
  2. Sublingual
  3. Buccal
  4. Rectal
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10
Q

What does parenteral mean

A

Taken into the body in a way other than through GIT

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11
Q

Give some way s a drug can be absorbed parenterally

A
  1. Subcutaneous
  2. intramuscularly
  3. intravenously
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12
Q

How can drugs pass through and get to their target site

A
  1. Diffuse passively
  2. Cells throng pores eg aqaporins
  3. Carrier to facilitate their transport into cells
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13
Q

How is insulin absorbed into the CNS

A

Pinocytosis or “cell drinking”

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14
Q

What dictates whether a drug can diffuse across a cell membrane

A

Lipid solubility and the concentration gradient

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15
Q

List some factor affecting oral absorption

A
  1. Disintegration of dosage forms
  2. Dissolution of particles
  3. Chemical stability of the drug
  4. Motility and mixing in the Gastrointestinal tract
  5. Presence and type of food
  6. Passage across gastrointestinal tract wall
  7. Blood flow to gastrointestinal tract
  8. Gastric emptying time
  9. Formulation
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16
Q

What is bioavailability

A

Is the proportion of the drug in a dosage form available to the body

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17
Q

When prescribing a drug what do we need to specify and why

A

The brand name as plasma concentration can vary between suppliers

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18
Q

Other than the drug type what else is important when giving medication

A

Mode of admin

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19
Q

Name the most bioavailable mode of admin

A

IV injection is 100%

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20
Q

Is bioavailability and synonymous with effectiveness

A

no a drug can be bioavailable but not clinically effective

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21
Q

What can first pass metabolism Also be called

A

first pass effect

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22
Q

What is first pass metabolism

A

Presystemic elimination

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23
Q

Where does first pass metabolism occur

A

The liver

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24
Q

What is first pass metabolism

A

When the liver does a thorough job metabolising some drugs that little is available to act via the systemic circulation

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25
Q

Give examples of drugs that are very effectively metabolised by the liver

A

Propranolol,
lidocaine,
GTN
`Verapamil

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26
Q

Does first past metabolism mean drugs have a high or lower bioavailability

A

low

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27
Q

What does a low availability mean we have to do

A

Give a very high oral dose compared to the amount needed to cause its beneficial effects

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28
Q

After absorption what happens to a drug

A

It is distributed to the body fluid compartments

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29
Q

What is volume distribution

A

A theoretical measure that illustrates how much volume you would need to keep the plasma concentration of a drug at a level of that administrated in the first place

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30
Q

How do we calculate the apparent volume Distribution of any given drug

A

the amount of drug present in the body divided by the concentration of a drug in the plasma

31
Q

What can kidney or liver failure lead to

A

Fluid retention causing an increase in volume distribution so bigger doses may have to be administrated

32
Q

What effect does dehydration have on volume Distribution

A

Dehydration conversely decreases volume Distribution so lesser doses are required to precent toxic effects occurring

33
Q

Where do most drugs diffuse

A

Between endothelial cells that make up capillaries into the interstitial tissue space

34
Q

Name the 5 body compartments

A
  1. Plasma 5%
  2. Interstitial 16%
  3. Intracellular 35%
  4. Transcellular 2%
  5. Body fat 20%
35
Q

Which body compartment does heparin affect

A

Plasma

36
Q

Which body compartment does warfarin affect

A

Plasma

37
Q

Which body compartment does gentamicin affect

A

Extracellular fluid

38
Q

Which body compartment does ethanol phenytoin affect

A

Total body water

39
Q

Plasma protein drugs bind to which hormone

A

Albumin and Alpha 1 acid glycoproteins

40
Q

What are free drugs

A

They are pharmacologically active and free to move to other compartments

41
Q

What happens to plasma protein drugs when they are in the kidney

A

They are NOT filtered out by the kidney

42
Q

How does blood supply affect drug effectiveness

A

The blood supply affects the equilibration of concentration of a lipid-soluble drug

43
Q

Why do enzymes process drug molecules

A

To increase, decrease or otherwise change the action of a drug

44
Q

How are most drugs broken down

A

Broken down into water soluble, inactive/less active compounds

45
Q

How are pro drugs absorbed

A

They are absorbed in a relatively inactive form and enzyme action converts them to a pharmacologically active metabolites

46
Q

What can explain variations In metabolism

A

Genetics

47
Q

Where in the body is the prime locus of metabolism and biotransformation

A

LIVER

48
Q

Which organs the than the liver also play a part in metabolism

A

Kidney
Skin
Gut
lungs

49
Q

Where does the liver receive blood and absorbed compounds from

A

The gut bypassing the heart

50
Q

How are drugs absorbed in the liver

A
  1. They enter through the gut
  2. Processed by the first pass effect
  3. Smooth endoplasmic reticulum contains the p450 enzymes
  4. Partially metabolised drugs re enter the systemic circulation for distribution
51
Q

What does the P450 enzyme do

A

It controls the concentration of absorbed drugs

52
Q

Name an enzyme that is abundantly expressed and used in more than half of clinically used drugs

A

Cytochrome P450 depended mixed function oxidases (CYPs)

53
Q

How can P450 enzymes be inhibited

A
  1. Competitive inhibitor

2. Non competitive inhibition

54
Q

What is competitive inhibitor

A

Competing fro the same enzyme

55
Q

What is non competitive inhibition

A

When one agent binds to the enzyme and prolongs the activity of the drug

56
Q

Where does most excretion of drugs occur

A

Via the kidneys in the urine

57
Q

How can small molecular weight drugs be removed

A

By glomerular filtration

58
Q

How are acids and bases excreted

A

They are actively transported in the proximal tubule

59
Q

How are lipid soluble drugs reabsorbed

A

Reabsorbed passively across the tubule cells

60
Q

Why are some drugs contraindicated in breast feeding mothers

A

As some drugs can travel to baby via breast milk

61
Q

Does excretion occur more via urine or faeces

A

urine

V v little excreted in faeces unless formulation poor or patient has diarrhoea

62
Q

How are volatile agents excreted

A

By the lungs

63
Q

How are large molecular weight drugs excreted

A

They are conjugated and excreted via bile

64
Q

What is pharmacokinetics

A

The study of ADME on a quantitative basis

65
Q

Give some examples go how we can study pharmacokinetics

A
  1. The half life in relation to plasma concentration/time plot
  2. Clearance rates
  3. Repeated dosing regimen
66
Q

What is first order kinetics

A

The amount of drug excreted compared to the concentration of the drug in the circulation

67
Q

For the majority of drugs what is the first order kinetics

A

They are directly proportional ie as time goes by, more drug is excreted

68
Q

What is plasma systemic clearance

A

It is the sum of all clearance processed of a drug

69
Q

Why might a drug have a sign half life

A

May be due to a low clearance rate, a high volume distribution or a combo

70
Q

Why might we administer multiple doses of a drug

A

So that the therapeutic window can be maintained without dramatic rises and fall in plasma concentration which could lead to rebound symptoms

71
Q

What is a loading dose

A

A one off larger dose

72
Q

Why might we give a loading dose

A

To help achieve the therapeutic target faster hastening the beneficial clinical effects of a drug

73
Q

What are the limitations of Pharmacokinetics

A
  1. You cant be sure that plasma conc is actually the same as the con of a drug at its target tissue e
  2. Drug response depends on conc in the immediate environment of its target

4th yr- CMS- Pharmacology and drugs (7 decks)

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