Pharmacokinetics

Question 1

What is pharmacokinetics

Answer 1

What the body does to drugs

Question 2

What are the 2 drug in stages

Answer 2

Absorption and metabolism

Question 3

What are the 2 drug out stages

Answer 3

Metabolism and elimination

Question 4

What are the 2 types of drug administration

Answer 4

Enteral and parenteral

Question 5

Give 3 examples of enteral delivery

Answer 5

Oral, sublingual and rectal

Question 6

Give 3 examples of parenteral administration

Answer 6

Intravenous, subcutaneous and intramuscular

Question 7

Where does the majority of drug absorption occur

Answer 7

Small intestine

Question 8

What is the typical transit time of drugs in the small intestine

Answer 8

3-5 hours

Question 9

What are 3 methods for drug absorption

Answer 9

Passive diffusion, facilitated diffusion and active transport

Question 10

What type of drugs are commonly by passive diffusion

Answer 10

Lipophilic drugs. Eg steroids and protonated weak acids/bases

Question 11

What does the diffusion of weak acids and bases depend on

Answer 11

Their pKa

Question 12

What type of transporters are involved in facilitated diffusion

Answer 12

Solute carrier transporters

Question 13

What are the 2 types of solute carrier transporters

Answer 13

Organic anion transporters or organic cation transporters

Question 14

What do SLCs allow the transport of

Answer 14

Charged (deprotonated p) drugs

Question 15

What are the secondary active transporters used in absorption

Answer 15

SLCs

Question 16

Give 3 physiochemical factors that affect drug absorption

Answer 16

GI length, drug lipophilicity and amount of SLCs

Question 17

Give 3 GI physiological factors that affect drug absorption

Answer 17

Blood flow, motility and pH

Question 18

Briefly explain what the first pass metabolism is

Answer 18

Where absorbed drugs travel to the liver via the hepatic portal Vein where the are metabolised before they reach systemic circulation

Question 19

What 2 enzymes are used in metabolising drugs

Answer 19

Phase I and II enzymes

Question 20

What is the result of first pass metabolism

Answer 20

Reduces availability of drugs reaching the systemic circulation

Question 21

What is bioavailability

Answer 21

The fraction of drugs which reaches it wh into a specific body compartment

Question 22

What calculations measures oral bioavailability

Answer 22

Amount reaching systemic circulation / total drug given by IV

Question 23

How do drugs travel throughout the body

Answer 23

Bulk flow then diffusion

Question 24

What is a barrier to diffusion

Answer 24

Capillaries permeability

Question 25

How does albumin affect drug distribution

Answer 25

It can bind to drugs reducing the amount of free drug available

Question 26

How does drug lipophilicity affect drug distribution

Answer 26

Highly lipophilic drugs diffuse better and so can travel further

Question 27

What is the volume of distribution

Answer 27

Represents the degree to which a drug is distributed in the body tissue rather than the plasma

Question 28

What does a higher volume of distribution indicate

Answer 28

The drug is highly distributed

Question 29

Is the volume of distribution is equal to the volume of plasma what does this suggest

Answer 29

All of the drug remains in the plasma

Question 30

What are the units of volume of distribution

Answer 30

Litres/Kg

Question 31

Where does drug metabolism largely take place

Answer 31

Liver

Question 32

What overall result do phase I and II enzymes have on drugs

Answer 32

Increase ionic charge to enhance renal elimination and conjugate drugs to stop reabsorption

Question 33

What are phase I enzymes known as

Answer 33

CYP450

Question 34

What do CYP450 enzymes do

Answer 34

Give drugs an increase dioxin charge by catalysing hydroxylation, dealkylation and redox reactions

Question 35

What do phase I drugs do to pro-drugs

Answer 35

Activate them

Question 36

Give an example of a pro drug and what it's activated to

Answer 36

Codeine to morphine

Question 37

What reactions do phase II enzymes catalyse

Answer 37

Sulphation. N-acetylation and Glutathione conjugation

Question 38

How many superfamilies of CYP are there

Answer 38

3

Question 39

Give 3 factor that affect drug metabolism

Answer 39

Age, sex and health

Question 40

What happens to the rate of elimination if YP450 enzymes are induced

Answer 40

Increases

Question 41

What is CBZ an example of

Answer 41

A CYP450 inducer

Question 42

What affect does CBZ have

Answer 42

Controls epilepsy

Question 43

What 2 methods are there to inhibit CYP450

Answer 43

Competitive and non competitive inhibitors

Question 44

If a CYP450 enzyme is inhibited then what happens to the plasma levels of the drug

Answer 44

Increase

Question 45

What is an example of a CYP459 inhibitor

Answer 45

Grapefruit juice

Question 46

What consequence does grapefruit juice have

Answer 46

Can reduce the blood pressure by too much and cause fainting

Question 47

What genetic factor do CYP enzymes show

Answer 47

Genetic polymorphism

Question 48

What is genetic polymorphism of CYP enzymes

Answer 48

How some CYP enzymes are expressed more than others in different nationalities

Question 49

What is the main route of drug elimination

Answer 49

Through the kidney

Question 50

What are the 3 processes involved in renal excretion

Answer 50

Glomerular filtration, active tubular secretion and passive tubular reabsorption

Question 51

What percentage of renal blood goes to the glomerulus

Answer 51

20%

Question 52

How much renal blood enters the kidney via the peritubular capillaries

Answer 52

80%

Question 53

What type of drug enters the kidney at the bowl as capsule

Answer 53

Unbound drug

Question 54

What has a high expression in the proximal tubule

Answer 54

OATs and OCTs

Question 55

What types of molecules are transported in the proximal tubule

Answer 55

Ionised molecules

Question 56

What happened during proximal tubular secretion to lipophilic drugs

Answer 56

Pass back into the blood

Question 57

What is clearance

Answer 57

Rate of elimination of a drug from the body

Question 58

What does volume of distribution and clear mice collectively predict

Answer 58

How long a drug stays in the body

Question 59

What is the drug half life

Answer 59

The amount of time over which the concentration of a drug in plasma decreases to half of its original concentration

Question 60

What is the formalin for working our half life

Answer 60

0.7 x Vd /CL

Question 61

What affects clearance

Answer 61

Heart, kidneys and liver

Question 62

When does zero kinetics occur

Answer 62

When there is a saturation of CYPs or transporters

Question 63

What does polypharmcy lead to

Answer 63

Zero kinetics and there's more competition for active sites

Question 64

What type of graph shows linear kinetics

Answer 64

Log graphs of time vs drug concentration in plasma

Question 65

What is the advantage of linear graphs

Answer 65

Can determine half lives easier