DRUG ABSORPTION, DISTRIBUTION,

Question 1

Talk through the journey of a drug through the body

Answer 1

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

Question 2

How do drugs enter the body

Answer 2

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

Question 3

What happens once a drug is absorbed into the body

Answer 3

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

Question 4

Where are drugs metabolised and excreted

Answer 4

Kidney and or liver

Question 5

What does ADME stand fro

Answer 5

Absorption
Distribution
Metabolism
Excretion

Question 6

For which drugs is the acronym ADME relevant for

Answer 6

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

Question 7

How can drugs be absorbed into the body

Answer 7

1. Enteral

2. Parenteral

Question 8

What is enteral

Answer 8

In or through the digestive system

Question 9

Give some way s a drug can be absorbed enterally

Answer 9

1. Oral
2. Sublingual
3. Buccal
4. Rectal

Question 10

What does parenteral mean

Answer 10

Taken into the body in a way other than through GIT

Question 11

Give some way s a drug can be absorbed parenterally

Answer 11

1. Subcutaneous
2. intramuscularly
3. intravenously

Question 12

How can drugs pass through and get to their target site

Answer 12

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

Question 13

How is insulin absorbed into the CNS

Answer 13

Pinocytosis or “cell drinking”

Question 14

What dictates whether a drug can diffuse across a cell membrane

Answer 14

Lipid solubility and the concentration gradient

Question 15

List some factor affecting oral absorption

Answer 15

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

Question 16

What is bioavailability

Answer 16

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

Question 17

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

Answer 17

The brand name as plasma concentration can vary between suppliers

Question 18

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

Answer 18

Mode of admin

Question 19

Name the most bioavailable mode of admin

Answer 19

IV injection is 100%

Question 20

Is bioavailability and synonymous with effectiveness

Answer 20

no a drug can be bioavailable but not clinically effective

Question 21

What can first pass metabolism Also be called

Answer 21

first pass effect

Question 22

What is first pass metabolism

Answer 22

Presystemic elimination

Question 23

Where does first pass metabolism occur

Answer 23

The liver

Question 24

What is first pass metabolism

Answer 24

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

Question 25

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

Answer 25

Propranolol, lidocaine, GTN `Verapamil

Question 26

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

Answer 26

low

Question 27

What does a low availability mean we have to do

Answer 27

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

Question 28

After absorption what happens to a drug

Answer 28

It is distributed to the body fluid compartments

Question 29

What is volume distribution

Answer 29

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

Question 30

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

Answer 30

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

Question 31

What can kidney or liver failure lead to

Answer 31

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

Question 32

What effect does dehydration have on volume Distribution

Answer 32

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

Question 33

Where do most drugs diffuse

Answer 33

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

Question 34

Name the 5 body compartments

Answer 34

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

Question 35

Which body compartment does heparin affect

Answer 35

Plasma

Question 36

Which body compartment does warfarin affect

Answer 36

Plasma

Question 37

Which body compartment does gentamicin affect

Answer 37

Extracellular fluid

Question 38

Which body compartment does ethanol phenytoin affect

Answer 38

Total body water

Question 39

Plasma protein drugs bind to which hormone

Answer 39

Albumin and Alpha 1 acid glycoproteins

Question 40

What are free drugs

Answer 40

They are pharmacologically active and free to move to other compartments

Question 41

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

Answer 41

They are NOT filtered out by the kidney

Question 42

How does blood supply affect drug effectiveness

Answer 42

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

Question 43

Why do enzymes process drug molecules

Answer 43

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

Question 44

How are most drugs broken down

Answer 44

Broken down into water soluble, inactive/less active compounds

Question 45

How are pro drugs absorbed

Answer 45

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

Question 46

What can explain variations In metabolism

Answer 46

Genetics

Question 47

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

Answer 47

LIVER

Question 48

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

Answer 48

Kidney Skin Gut lungs

Question 49

Where does the liver receive blood and absorbed compounds from

Answer 49

The gut bypassing the heart

Question 50

How are drugs absorbed in the liver

Answer 50

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

Question 51

What does the P450 enzyme do

Answer 51

It controls the concentration of absorbed drugs

Question 52

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

Answer 52

Cytochrome P450 depended mixed function oxidases (CYPs)

Question 53

How can P450 enzymes be inhibited

Answer 53

1. Competitive inhibitor | 2. Non competitive inhibition

Question 54

What is competitive inhibitor

Answer 54

Competing fro the same enzyme

Question 55

What is non competitive inhibition

Answer 55

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

Question 56

Where does most excretion of drugs occur

Answer 56

Via the kidneys in the urine

Question 57

How can small molecular weight drugs be removed

Answer 57

By glomerular filtration

Question 58

How are acids and bases excreted

Answer 58

They are actively transported in the proximal tubule

Question 59

How are lipid soluble drugs reabsorbed

Answer 59

Reabsorbed passively across the tubule cells

Question 60

Why are some drugs contraindicated in breast feeding mothers

Answer 60

As some drugs can travel to baby via breast milk

Question 61

Does excretion occur more via urine or faeces

Answer 61

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

Question 62

How are volatile agents excreted

Answer 62

By the lungs

Question 63

How are large molecular weight drugs excreted

Answer 63

They are conjugated and excreted via bile

Question 64

What is pharmacokinetics

Answer 64

The study of ADME on a quantitative basis

Question 65

Give some examples go how we can study pharmacokinetics

Answer 65

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

Question 66

What is first order kinetics

Answer 66

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

Question 67

For the majority of drugs what is the first order kinetics

Answer 67

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

Question 68

What is plasma systemic clearance

Answer 68

It is the sum of all clearance processed of a drug

Question 69

Why might a drug have a sign half life

Answer 69

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

Question 70

Why might we administer multiple doses of a drug

Answer 70

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

Question 71

What is a loading dose

Answer 71

A one off larger dose

Question 72

Why might we give a loading dose

Answer 72

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

Question 73

What are the limitations of Pharmacokinetics

Answer 73

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