Introduction to Pharmacology

Question 1

Pharmacodynamics vs Pharmacokinetics

Answer 1

Pharmacodynamics is how a drug affects the body

Pharmacokinetics is how the body affects the drug

Question 2

General ligand-receptor

Answer 2

Receptors lie on the cell boundary, ligands bind extracellularly which then triggers an intracellular signal, this cascades into a biological action

Question 3

Channel linked receptors

Answer 3

Ligand binds to a recepter on an ion channel which can either signal the channel to open or close

Question 4

G-protein coupled receptors

Answer 4

Interacts with a g-protein which in turn interacts with an ezyme activator or ion channel. So it indirectly interacts with these vis the g-protein

Question 5

Enzyme (or Kinase) linked receptors

Answer 5

These directly initiate enzymatic interactions

Question 6

Nuclear receptors

Answer 6

This stimulates messenger RNA synthesis in the cell nucleus leading to protein synthesis

They are intracellular

Question 7

3 drug targets other than receptors

Answer 7

• Channel blockers, these target ion channels but block them instead of binding to a receptor on the channel
• Ezymes, these drugs directly target an enzyme
• Protein transporters, this target proteine transporters in order to enter a cell

Question 8

Max drug response

Answer 8

This occurs when all the drug targets are already targeted and hence saturated. At this point increasing the dose won’t increase the response.

Question 8

What is ED50

Answer 8

This is the dose at which 50% of the maximum response is reached

Question 8

What is therapeutic index

Answer 8

This is the ratio of the ED50 of the desired effect and the ED50 of the adverse effect

Question 9

What is a competative antagonist

Answer 9

These are molecules which bind to the same receptors as an agonist but don’t cause any intracellular signal transduction

Question 10

Efficacy vs Potency

What do both of them mean and which of these drugs is more efficatious/potent

Answer 10

Efficacy is how large a response the drug has and potency is how much you need to produce an effect.

Drug C is the most potent and drug A is the most efficatious

Question 10

What is a non-competative antagonist

Answer 10

These are molecules which don’t bind to the receptors but block further signal transduction

Question 11

What does selectivity mean?

Answer 11

This is how specifically a receptor is targeted, if a drug bind to two different receptors equally then it is not very selective, but if it binds to one a lot better than another then it is highly selective.

Question 12

Tachyphylaxis vs Tolerance

Answer 12

Tachyphylaxis is where desensitisation occurs rapidly whereas tolerance occurs gradually

Question 13

4 reasons why drug desensitisation occurs

Answer 13

1. The number of receptors reduce
2. The structure of receptors or their function changes
3. Mediators become exhausted
4. Physiological adaption, the body produces physiological responses to counter the effects of the drug

Question 14

What does it mean for a drug to survive “first pass metabolism”

Answer 14

First pass metabolism occurs through oral ingestion and is when a drug is metabolised by enzymes either in the intestine or the liver before it can reach the blood.

Question 15

What is bioavailability?

Answer 15

This is how much of the drug makes it into the circulatory system and stays in the circulatory system.

In the graph below the ratio of the two areas under each line is the bioavailability, in this case it is 30% if taken orally

Question 16

3 types of drug diffusion accross a membrane

Answer 16

1. Passive
2. Pore mediated
3. Pinocytosis (large drug drags a whole part of the membrane with it to enter)

Question 18

Protein binding of drugs and what this can mean

Answer 18

This is how efficiently a drug binds to proteins. A drug bound to proteins in blood plasma can’t diffuse into the interstitial fluid however it also can’t be eliminated from the blood.

The ratio of free drug to bound drug remains the same as the more free drug there is the more becomes bound.

Drugs that are highly protein bound are long acting and have long half lives.

They are also affected by things that affect blood plasma such as pregnacy, disease and age

Question 18

Apparent volume of distribution

Answer 18

This is the total amount of the dosage administered divided by concentration in blood plasma.

Theoretically this tells you the apparent amount of plasma required to carry your dose at the measure concentration. But clinically it is essentially a measure of how much the drug has spread out into the body.

A higher apparent volume of distribution means the drug has spread into the body well, a lower means most has remained in the blood plasma.

Question 19

Organs responsible for drug metabolism

Answer 19

Primarily metabolised by the liver however they can also be metabolised by the kidneys, lungs and skin

Question 20

What are the two phases of drug metabolism?

Answer 20

1. Phase 1: reacted into an in active compound
2. Phase 2: reacted into a soluable compound for excretion

Question 21

Why is it important for drugs to be water soluable during excretion?

Answer 21

If a drug is lipid soluable it will be able to pass through lipid membranes and re-absorb into the body from urine

Question 22

Renal vs Biliary excretion

Answer 22

Renal excretion occurs with small drugs < 300Da and Biliary excretion occurs with large drugs > 300Da

Question 23

Family of liver enzymes responsible for phase 1 metabolism

Answer 23

Cytochrome P450 emzymes

Question 25

First order kinetics

Answer 25

Also known as exponential kinetics, concentration follows a typical half life pattern.

This is most typical as concentrations of the drug will affect the ammount that is metabolised

Question 26

Zero order kinetics

Answer 26

This is where the ability to metabolise is maxed out very quickly hence a continous ammount is matabolised no matter what the concentration. An example include ethanol and aspirin.

Question 27

What is steady state? If you dose once every halflife when is it reached?

Answer 27

This is where the rate at which a drug is being metabolised equals the rate of adminstration.

If you dose once every halflife then this is considered reached after 5 halflives.

Question 29

Long vs Short half life advantages and disadvantages

Answer 29

Long:
* Patients don’t have to take it as regularly and the steady state is rather stable however it take longer to reach steady state
Short
* Has to be taken really regularly however as steady state is reached quickly you can play around with it lots more easily

Question 30

What are beta 2 receptors responsible for?

Answer 30

Beta 2 receptors are predominantly present in airway smooth muscles.

When bound the airways relax

Question 31

What are beta 1 receptors responsible for?

Answer 31

Found throughout the sypathetic nervous system including the heart and are activated by adrenaline and noradrenaline