Pharmacology

Question 1

What is an agonist?

Answer 1

Drug that occupies receptor and activates a process

Question 2

What is an antagonist?

Answer 2

Drug that binds to receptor and inhibits a process

Question 3

What is a competitive antagonist?

Answer 3

Binds to receptor site (competes for same receptor)

Question 4

What is a non-competetive antagonist?

Answer 4

Binds to a different site, changes shape or function of receptor preventing binding / effect (allosteric inhibition)

Question 5

Define potency

Answer 5

Amount of drug required to produce given effect

Question 6

Define efficacy

Answer 6

Maximal effect that a drug produces irrespective of concentration

Question 7

Define TD50

Answer 7

Median dose required to produce toxic effect of 50% of species

Question 8

Define LD50

Answer 8

Median dose required to produce lethal effect in 50% of species

Question 9

What is tachyphylaxis?

Answer 9

Sudden decrease in response to drug (e.g. GTN)

Question 10

What is a chemical antagonist and give an example?

Answer 10

Binds to a drug rendering it ineffective (protamine to heparin)

Question 11

What is a physical antagonist and give an example?

Answer 11

Binds to drug to prevent absorption e.g. charcoal

Question 12

What is a physiological antagonist and give an example?

Answer 12

Effect occurs through secondary physiological process e.g. glucocorticoids lead to increase in blood sugar

Question 13

Draw a dose response curve showing agonist and effect of competitive antagonist

Answer 13

Adding an antagonist increases the amount of agonist required (shifts to right along log scale) to produce the required effect but does not affect the overall maximum response

Question 14

Draw a dose response curve showing agonist + irreversible antagonist

Answer 14

Adding an irreversable antagonist decreases the maximum response (e.g. less efficacy)

Question 15

Draw a dose response curve showing full vs partial agonist

Answer 15

Full agonist reaches full efficacy whereas partial agonist only produces a partial response. e.g tramdol vs fentanyl

Question 16

What is a pro-drug and give an example?

Answer 16

Inactive precursor chemical that must be absorbed and converted to the active drug - e.g. codeine

Question 17

Name 4 mechanisms of drug permeation

Answer 17

1. Aqueous diffusion though tight junctions / aqueous pores 2. Lipid diffusion 3. Special carriers (for large molecules e.g. glucose, proteins) 4. Exocytosis / endo cytosis (e.g. blood brain barrier)

Question 18

What is Ficks law

Answer 18

Concentration gradient x (area / permeability) / thickness (e.g. things that affect = concentration gradient / increased area = higher rate of diffusion higher permeability = higher rate of diffusion higher thickness = lower rate of diffusion

Question 19

How does pH affect drug permeability? Explain how urine prevents reabsorption

Answer 19

Ionised drugs are polar and therefore have less ability to permeate membranes depending on pH. Urine has a lower pH and therefore more of the drug is ionised and less likely to pass back into the body via membranes

Question 20

Is aspirin a weak acid or weak base

Answer 20

Weak acid (salicylic acid) - dissociates into aspirin anion and H+

Question 21

Explain the following dose response curve - an irreversable antagonist is administered in increasing doses

Answer 21

In lower doses the maximum effect is preserved. As the concentration of the irreversable antagonist is increased all the available receptors are taken up and maximum effect is reduced

Question 22

Name an example of a partial agonist

Answer 22

Buprenorphine (partially activates opioid receptors but does not produce full effect)

Question 23

Name two examples of second messengers

Answer 23

cAMP and calcium

Question 24

Drug A is more _________________ than Drug B

Answer 24

Effective (higher maximum response)

Question 25

Drug A is more _________________ than drug C

Answer 25

Potent (lower dose required to achieve same response)

Question 26

Define volume of distribution

Answer 26

Amount of drug in body related to concentration (e.g. amount of drug in body / concentration)

Question 27

Define clearance

Answer 27

Rate of elimination over concentration

Question 28

Define formula for elimination

Answer 28

Rate of elimination = CL x C (clearance x concentration)

Question 29

3 factors affecting bioavailability

Answer 29

Absorption, first pass elimination, rate of absorption

Question 30

Name an example of CYP inhibitor

Answer 30

Grapefruit juice, macrolides

Question 31

Name an example of CYP inducer

Answer 31

Smoking, alcohol, St Johns Wart