Pharmacology

Question 1

Define ‘pharmacology’

Answer 1

The study of substances that interact with living systems through chemical processes

Question 2

Define ‘drug’

Answer 2

Any substance that interacts with a molecule which plays a regulatory role in living systems

Question 3

What is a ‘competitive antagonist’?

Answer 3

Binds to and competes for receptor but elicits no reaction

Question 4

What is a chemical antagonist?

Answer 4

Substance that binds directly to an agonist molecule to prevent it from binding to the active site

Question 5

What is a physiological antagonist?

Answer 5

When two substances have exactly opposite actions and work via different pathways

Question 6

What is ‘pharmacodynamics’

Answer 6

the action of a drug on the body

Question 7

What is pharmacokinetics?

Answer 7

The action of the body on a drug

Question 8

What do drugs tend to be? (related to pH)

Answer 8

weak acids or bases

Question 9

When are drugs lipid-soluble?

Answer 9

In their undissociated (non-charged) form

Question 10

When are drugs water-soluble

Answer 10

In their dissociated (charged) form

Question 11

What can activated charcoal be used for?

Answer 11

Absorbing substances in the GI tract, especially those from overdose

Question 12

How may you treat a TCA overdose and why?

Answer 12

TCA is a weak acid so can be treated by trying to alkalinise the blood to cause dissociation into water-soluble form in order to prevent diffusion back into the blood from the renal tubule

Question 13

How may you treat an amphetamine overdone and why?

Answer 13

Amphetamines are weak base so acidify urine by administering ammonium chloride in order to increase excretion

Question 14

Define ‘drug specificity’

Answer 14

The ability of a drug to act on a particular location alone

Question 15

Define ‘drug selectivity’

Answer 15

The ability to produce a particular effect as a result of the structural specificity of drug binding to receptors

Question 16

What are the 4 different types of bond? (order in terms of strength)

Answer 16

Covalent, electrostatic, hydrophobic and van der waals

Question 17

What does ‘EC50’ represent?

Answer 17

The concentration of drug that gives a half-maximal response

Question 18

How does EC50 change in the presence of competitive antagonists?

Answer 18

Need to add more drug in order to reach EC50

Question 19

How does EC50 change in the presence of non-competitive antagonists?

Answer 19

The maximal effect of the drug is reduced, but the EC50 therefore remains the same

Question 20

Define ‘efficacy’

Answer 20

The greater the effect of the drug, the greater the efficacy

Question 21

Define ‘potency’

Answer 21

The concentration of a drug required for that effect to have the same efficacy

Question 22

What is volume of distribution?

Answer 22

Amount of drug in body/plasma concentration - it is a measure of the distribution of the drug around the body

Question 23

What protein may drugs bind to?

Answer 23

Albumin in the blood

Question 24

What are the properties of ‘bound’ drugs (to proteins)?

Answer 24

They cannot be metabolised, excreted or diffuse through structures, they are inactive

Question 25

What happens if you stop or start a drug that binds to a protein?

Answer 25

It changes the level of other protein-bound drugs and can lead to both drugs having sub-therapeutic levels

Question 26

What are the 4 types of receptor drugs may act on? (order in terms of fast to slow)

Answer 26

Ligand-gated ion channel, G protein-coupled receptor, receptor tyrosine kinases and nuclear receptors

Question 27

Define ‘tachyphylaxis’

Answer 27

Reduced drug effect in a short time scale

Question 28

Define ‘tolerance’

Answer 28

Reduced drug effect when given over a long period of time

Question 29

What may be the cause of tachyphylaxis and tolerance?

Answer 29

Receptor loss or desensitisation, physiological adaptation, exhaustion of mediators, increased metabolic degradation or receptor internalisation

Question 30

How does salbutamol act?

Answer 30

It’s a B2 adrenergic receptor agonist

Question 31

Why may tachyphylaxis occur with salbutamol?

Answer 31

There is polymorphism of the B2 adrenergic receptor on which salbutamol acts

Question 32

Which routes of drug administration experience first pass metabolism?

Answer 32

Oral and rectal; go to liver prior to entry to systemic circulation

Question 33

What is the ‘first pass effect’?

Answer 33

All drugs absorbed by GI tract enter the portal blood supply and travel to the liver where they are metabolised by enzymes before entering the systemic blood supply

Question 34

What is involved in phase I reactions?

Answer 34

Biotransformations to make substances more water-soluble (polar) as well as reduction, hydrolysis and oxidation (CYP450 involved) reactions

Question 35

What is involved in phase II reactions?

Answer 35

Entry to phase II if still not polar enough after phase I, conjugation (adding large molecule such as glucose to increase water-solubility) and synthesis

Question 36

What is meant by ‘clearance’?

Answer 36

The rate of elimination/concentration remaining

Question 37

Define ‘half-life’

Answer 37

time for the drug plasma concentration to halve

Question 38

How do you calculate drug half life?

Answer 38

volume distribution/clearance x 0.7

Question 39

Define ‘zero order metabolism’

Answer 39

Where elimination is constant per unit of time, so graph is linear, this only occurs when the elimination system is saturated (ethanol)

Question 40

Define ‘first order metabolism’

Answer 40

Elimination of constant fraction of drug per unit of time (bell shaped graph), so the half-life is always constant

Question 41

Define ‘loading dose’

Answer 41

Larger than normal dose used to get individual into therapeutic window more quickly

Question 42

Define ‘maintenance dose’

Answer 42

Keeps the drug in therapeutic range