ICPP

Question 1

Kd and relationship to affinity

Answer 1

The higher the Kd the lower the affinity

Question 2

Definition of Bmax

Answer 2

The maximum number of free receptors that can be saturated

Question 3

Affinity

Answer 3

The degree to which the drug tends to bind to the receptor

Question 4

Efficacy

Answer 4

The ability to produce the desired response

Question 5

EC50

Answer 5

The effective concentration that gives 50% of the maximal response - known as drug potency

Question 6

Emax

Answer 6

The maximal response that can be given

Question 7

Concentration

Answer 7

The concentration refers to the known concentration of a drug at the site of action

Question 8

Dose

Answer 8

The concentration at site of action is generally unknown

Question 9

Spare receptors

Answer 9

Spare receptors don’t add to the size of a response

They increase the sensitivity and potency - allow responses at lower concentrations

Question 10

Partial agonist

Answer 10

They bind to receptor and don’t elicit a maximal response

They have a lower intrinsic activity as lower efficacy

Question 11

Reversible antagonist

Answer 11

Compete with agonist for receptors.

This inhibition is surmountable

Causes shift to the right

Question 12

Irreversible antagonism

Answer 12

The antagonist dissociates slowly or not at all

This is non-surmountable

This will cause a a right ward shift and a smaller response with high antagonist concentrations

Question 13

Non-competitive antagonist

Answer 13

The antagonist binds to an allosteric site
No competition for biding site
Similar effect to irreversible competitive antagonists

Question 14

Main processes in drug therapy

Answer 14

Absorption
Distribution
Metabolism
Excretion

Question 15

Drug administration

Answer 15

Oral 
Sublingual 
Rectal 
Intravenous 
Subcutaneous 
Intramuscular

Question 16

Drug absorption - lipophilic drugs

Answer 16

Passive diffusion - cross GI epithelia

Steroids

Question 17

Drug absorption - charged and hydrophilic drugs

Answer 17

Facilitated diffusion using solute carrier proteins

Passive process

Question 18

Solute carrier proteins - active process

Answer 18

SLC can also enable drug transport in GI using secondary active transport
They don’t utilise ATP but rather a pre-existing electrochemical gradient

Question 19

Factors affecting drug absorption

Answer 19

Physicochemcial factors - GI length and SA
GI physiology - blood flow, pH
First pass metabolism - enzymes can denture the drugs-liver

Question 20

First pass metabolism

Answer 20

Reduces availability of drug reaching systemic

circulation - therefore affects therapeutic potential

Question 21

Bioavailability

Answer 21

Fraction of dose which reaches the specific body compartment intended

Question 22

Factors affecting drug distribution

Answer 22

Drug lipophilicity or hydrophilicity
Capillary permeability
Degree of drug binding to plasma or proteins

Question 23

How does Vd - volume of distribution - affect the penetration

Answer 23

Smaller Vd values = less penetration

Larger Vd values = more penetration

Question 24

Where does drug metabolism usually occur

Answer 24

Liver

Question 25

Which enzymes do Phase 1

Answer 25

Cytochrome P450 enzymes

Question 26

What do cytochrome P450 enzymes do?

Answer 26

They are versatile generalists which catalyse the drugs | This causes the drugs to have an increased ionic charge

Question 27

Phase 2 metabolism

Answer 27

Carried out by hepatic enzymes - mainly cytosolic Generalists but faster Enhance hydrophilicity by increasing ionic charge further

Question 28

Factors affecting drug metabolism

Answer 28

Age Sex General health Certain drugs can inhibit or induce cytochrome P450 enzymes

Question 29

CYP450 induction

Answer 29

Constant use of certain drugs can induce CYP450 isozymes This will cause slower degradation If another drug is metabolised using these enzymes its rate if elimination will increase Drug levels will fall

Question 30

CYP450 inhibition

Answer 30

Constant use of cortina drugs can inhibit CYP450 isozymes This will cause a slower rate of elimination in drug by these enzymes This will cause drug levels to increase

Question 31

Main route of drug elimination

Answer 31

Kidney

Question 32

Three processes of drug elimination.

Answer 32

Glomerular filtration Active tubular secretion Passive tubular reabsorption

Question 33

Glomerular filtration

Answer 33

Unbound drug enters Bowman’s capsule | 20% renal blood flow

Question 34

Proximal tubular secretion

Answer 34

Remaining 80% of blood enters by organ cation and anion transporters

Question 35

Distal tubular reabsorption

Answer 35

Passive reabsorption of lipid soluble and uncharged drugs

Question 36

Clearance

Answer 36

The volume of plasma that is completely cleared of the drug per unit of time

Question 37

Drug half life

Answer 37

The amount of time over which the concentration of a drug in the plasma has decreased to a half of that when first measured If Vd increases so does half life If clearance increases half life decreases

Question 38

isoelectric point

Answer 38

The isoelectric point of a protein is the pH at which there is no overall net charge