Pharmacokinetics + Pharmacodynamics

Question 1

List the phases of drug absorption (4)

Answer 1

1. Absorption
2. Clinical effect
3. Metabolism
4. Excretion

Question 2

Define enteral drug administration

Answer 2

Administered via the gut

Question 3

Define parental drug administration

Answer 3

Not administered via the gut

Question 4

List forms of drug administration (5)

Answer 4

1. Oral
2. Intravenous
   - Injected through a vein straight into bloodstream
3. Intramuscular
   - Injected through a muscle
4. Subcutaneous
   - Injected under skin to fatty tissue
5. Inhalation
   - Absorbed through lungs

Question 5

What form of parenteral drug administration works slowly?

Answer 5

Subcutaneous- has to pass through more

Question 6

Advantages of oral administration

Answer 6

Socially acceptable

Question 7

Disadvantages of oral administration (4)

Answer 7

1. Slow onset
2. Variable absorption
3. Gastric acid may destroy drug
4. 1st pass metabolism

Question 8

List some other factors affecting oral drug absorption (5)

Answer 8

1. Lipid solubility and ionisation
2. Drug formulation
3. Gastrointestinal motility
4. Interactions with other substances in the gut
5. GI tract disease

Question 9

Define 1st pass metabolism

Answer 9

When drug conc is greatly reduced before it reaches the systemic circulation

• Because the liver metabolises the drug

Question 10

Where does all blood from the GI tract drain to?

Answer 10

Hepatic portal vein

Question 11

What veins in the GI tract do not drain to the hepatic portal vein?

Answer 11

Sublingual and rectal veins

Question 12

What does the HPV drain to

Answer 12

Liver

Question 13

What happens when the liver inactivates the drug?

Answer 13

More needed by oral route to get desired effect (e.g. glyceryl trinitrate)

Question 14

What happens when the liver activates the drug?

Answer 14

Makes an active form of an inactive drug
Less needed by oral route
(e.g.Valaciclovir —> Aciclovir )

Question 15

Disadvantages of non oral drug administration (3)

Answer 15

1. Allergic reactions most severe
2. Access difficulties/self medication
3. Drug cost higher

Question 16

What are the advantages of non oral drug administration?

Answer 16

Predictable plasma levels

No first pass metabolism

Question 17

1st pass metabolisism is important when considering drug dosage

What can abnormal liver function cause? (3)

Answer 17

1. Extremes of life
2. Liver disease
3. Drug interactions changing drug metabolism

Question 18

Why is there a difference in severity with relation to oral and non-oral drug administration?

Answer 18

ORAL
- Allergic reaction not as dangerous as there could be 30 minutes before the drug has an effect

NON ORAL
- Allergic reaction more severe as the drug goes straight to the blood so there is less time to act

Question 19

Define the term bioavailability

Answer 19

Proportion of an ingested drug that is available for clinical effect

Question 20

What factors modify the bioavailability?

Answer 20

1. Dosage form
2. Destruction in the gut
3. Poor absorption
4. 1st pass metabolism

Question 21

When would you want the bioavailability of a drug to be as low as 0%?

Answer 21

If you want to keep the drug working in the gut and not have it go into the bloodstream

Question 22

Define drug distribution

Answer 22

How much of the body is the drug diluted in?

Question 23

Where in the body are drugs diluted in?

Answer 23

Vascular
Tissues
CNS

Question 24

How does lipid binding affect the volume of distribution?

Answer 24

Creates a slow release from accumulation

Question 25

What happens if a drug bound to a plasma protein is inactive?

Answer 25

Can act as a reservoir

Question 26

How can plasma proteins act as a reservoir for drugs?

Answer 26

If the drug is used up, the plasma protein releases more so allows the reaction to act for much longer

Question 27

Give examples of drugs that can interact by competitive binding.

Answer 27

Warfarin + Aspirin

Question 28

Define drug metabolism

Answer 28

Preparing the drug from elimination from the body

Question 29

Give examples of phase 1 reactions of drug metabolism (3)

Answer 29

- Oxidation - Reduction - Hydrolysis

Question 30

What is the effect of phase 1 metabolism?

Answer 30

Conversion to metabolites of lesser, equal or greater activity- changes its shape

Question 31

Give examples of phase 2 reactions of drug metabolism (4)

Answer 31

- Conjugation - Sulphation - Methylation - Acetylation

Question 32

What is the effect of phase 2 metabolism?

Answer 32

Conversion to inactive metabolites- add to larger molecule that the body naturally eliminates

Question 33

List examples of drug excretion (5)

Answer 33

1. Renal - urine 2. Liver - bile 3. Lungs - exhale gas 4. Sweat 5. Saliva

Question 34

List disorders of excretion (2)

Answer 34

1. Renal disease | 2. Liver disease

Question 35

How does chronic renal failure (from renal disease) affect drug administration?

Answer 35

Drug doses must be reduced

Question 36

How does liver failure (from liver disease) affect drug administration?

Answer 36

Drug doses must be reduced

Question 37

Do drugs distribute themselves evenly around the body?

Answer 37

No- normally go to places where blood flow is higher and eventually even out

Question 38

What is planning drug use based on?

Answer 38

The idea of body compartments

Question 39

How does the drug behave in a single compartment model?

Answer 39

Drug behaves as if it is evenly distributed throughout the body

Question 40

How does the drug behave in a two compartment model?

Answer 40

Drug behaves as if it is in equilibrium with different tissues in the body

Question 41

Define pharmacokinetics

Answer 41

Study of how an organism affects the drug

Question 42

How is pharmacokinetics studied? (2)

Answer 42

1. Drug clearance | 2. Repeated drug dosing

Question 43

What features are involved in drug clearance? (3)

Answer 43

1. Plasma half life (time for 1/2 drug to be removed) 2. 1st order kinetics 3. 0 order kinetics

Question 44

What form of diffusion does drug elimination/absorption occur through?

Answer 44

Passive diffusion

Question 45

How is drug removal related to the drug concentration in first order kinetics? (2)

Answer 45

- Drug removal is proportional to the drug concentration | - Logarithmic graph of elimination is a straight line

Question 46

What can drug elimination be saturated by?

Answer 46

High drug concentrations

Question 47

What happens during zero order kinetics in relation to drug elimination?

Answer 47

Constant amount of drug is eliminated per unit time

Question 48

What happens during a paracetamol overdose? (3)

Answer 48

- Can cause irreversible liver damage which can affect blood clotting - It is metabolised by zero order kinetics - It is toxic to the liver but not many other places

Question 49

What could too frequent a dosing schedule of drugs result in?

Answer 49

Plasma levels that may be toxic

Question 50

What does the dosing schedule of drugs depend on?

Answer 50

The drugs therapeutic index

Question 51

What could too infrequent a dosing schedule of drugs result in?

Answer 51

Sub-therapeutic plasma levels and no clinical effect

Question 52

How can drugs affect each other?

Answer 52

One drug may increase or decrease the metabolism of another

Question 53

What form of drug absorption is the least reliable?

Answer 53

Oral route