Pharmacokinetics and Pharmacodynamics

Question 1

What are the phases of drugs passing through the body

Answer 1

absorption
clinical effect
metabolism
excretion

Question 2

What are the different routes of administration

Answer 2

Oral
Intravenous
Intramuscular
Subcutaneous
Inhalation

Question 3

Advantages and disadvantages of oral administration

Answer 3

Advantages
- socially acceptable

Disadvantages

• slow onset
• variable absorption
• gastric acid may destroy drug
• ‘first-pass’ metabolism

Question 4

What other factors affect oral absorption

Answer 4

• lipid solubility and ionisation
• drug formulation
• gastrointestinal motility
• interactions with other substances in the gut
• GIT disease

Question 5

Describe the issue of first pass metabolism

Answer 5

All blood from the GI tract drains to the
hepatic portal vein (except sublingual and rectal veins)

Hepatic portal vein drains to the LIVER

Drug only reaches systemic circulation
AFTER passing through the liver once

Question 6

What can the liver do to the drug.

Examples?

Answer 6

Metabolises it
either:
inactivates drug - More needed by oral route to get desired clinical effect
e.g glyceryl trinitrate

activates drug - Makes an active form of an inactive drug, less needed by oral route
e.g. valaciclovir –> aciclovir

Question 7

when is it important to consider first pass metabolism

Answer 7

when considering drug dosage if normal, or abnormal liver function (extremes of life, liver disease, drug interactions changing drug metabolism)

Question 8

What are the advantages and disadvantages of non-oral administration?

Answer 8

advantages

• predictable plasma levels
• no first pass metabolism

disadvantages

• allergic reactions more severe
• access difficulties/ self medication
• drug cost higher

Question 9

what does bioavailability mean?

Answer 9

proportion of an ingested drug that is available for clinical effect

Question 10

what is bioavailability modified by

Answer 10

dosage form
destruction in the gut
poor absorption
first pass metabolism

Question 11

what does the term ‘volume of distribution’ mean?

Answer 11

how much of the body is the drug diluted in ?

- compartments (vascular, tissues, CNS (?)

Question 12

How are drugs distributed?

Answer 12

lipid binding
- slow release from accumulation)

drug binding to plasma proteins

• bound drug is inactive (can act as a reservoir)
• drug interactions possible by competitive binding (warfarin and aspirin)

?

Question 13

What does drug metabolism do

Answer 13

preparing the drug from elimination from the body?

Question 14

What is involved in drug metabolism

Answer 14

Phase 1 reactions

• oxidation
• reduction
• hydrolysis

Phase 2 reactions
- conjugation (Glucuronidation, sulphation, methylation,
acetylation, glutathione)

Question 15

How are drugs excreted

Answer 15

renal - urine
liver - bile
lungs - exhale gas
sweat
saliva

Question 16

How can you modify renal excretion?

Answer 16

?

Question 17

How can you modify renal excretion?

Answer 17

by modifying the pH?????

Question 18

Give 2 disorders of excretion

Answer 18

renal disease
- chronic renal failure (drug doses must be reduced)

liver disease
- liver failure (drug doses must be reduced)

Question 19

Do drugs distribute themselves evenly thoughout the body?

Answer 19

No

Question 20

What is the planning of drug use based upon?

Answer 20

body compartments

Question 21

What is the single compartment model?

Answer 21

drug behaves as if it is evenly distributed

throughout the body

Question 22

What is the two compartment model

Answer 22

Drug behaves as if it is in equilibrium with

different tissues in the body

Question 23

What notable difference is there between the one and two compartment models

Answer 23

two compartment model takes longer to distribute around the whole body. Immediately after administration the drug is located in specific sites before spreading

Question 24

What is important about drug clearance

Answer 24

Knowing the plasma half-life

First order kinetic
zero order kinetics

Question 25

In first order kinetics how does drug elimination or absorption happen

Answer 25

Passive diffusion only

Question 26

in first order kinetics, what is drug removal proportional to

Answer 26

drug concentration

Question 27

What does a first order kinetics log graph or elimination look like? What does this tell you about the length of half life?

Answer 27

straight line

it’s constant

Question 28

How does zero order kinetics occur?

Answer 28

Drug elimination is an ACTIVE
process and can be saturated by high
drug concentrations

Question 29

What does a graph look like for zero order kinetics?

Answer 29

linear graph of drug elimination

Question 30

Define first order elimination

Answer 30

The amount of drug eliminated per unit time is proportional to [C]; a constant % of drug is eliminated per unit time

Question 31

Define zero order elimination

Answer 31

A constant amount of drug is eliminated per unit time

Question 32

What is drug accumulation

Answer 32

how the plasma concentration build if repeated doses of a drug are given

Question 33

What may too frequent a dosing schedule result in

Answer 33

plasma levels that my be toxic (depends upon the drug#s therapeutic index)

Question 34

What may too infrequent a dosing schedule result in

Answer 34

subtherapeutic plasma levels and no clinical

effect

Question 35

What is knowledge of pharmakinetics important for

Answer 35

planning dosing schedules

Question 36

How might one drug affect another

Answer 36

may increase or reduce the metabolism of another

Question 37

What is the least reliable route of drug absorption

Answer 37

oral