Wk 10

Question 1

What is pharmacokinetics?

Answer 1

Relationship between dose and drug conc. at site of action and time course of drug conc. in body.

How the body affects the drug

Question 2

What is the four categories that influence drug conc. at site of action (ADME)?

Answer 2

1. Absorbed into body fluids
2. Distributed into sites of action
3. Metabolised into inactive/active
4. Excreted by body in various ways

Question 3

What are the types of routes of administration?

Answer 3

Enteral - GIT
1. Oral - mouth
2. Inhalation - lungs
3. Epithelial - topical applied to skin
4. Sublingual - under tongue
5. Rectal - rectum

Parenteral - by injection
6. Intravenous - blood
7. Intramuscular - muscle
8. Subcutaneous - under the skin
9. Intrathecal - spine

Question 4

What are the advantage and disadvantage of enteral drug routes?

Answer 4

Advantages:
- Easy to administer
- Increased adherence

Disadvantages:
- High GIT
- First pass metabolism (inactivated as soon as it enters the liver, can’t reach any target sites in other body systems)

Question 5

What are the advantage and disadvantage of parenteral drug routes?

Answer 5

Advantages:
- Avoids first pass metabolism (can reach other body systems)
- Can deliver large drug quantities

Disadvantages:
- Risk of infection
- Painful/difficult to administer
- Overdose risk

Question 6

What are the three main factors that affect drug absorption?

Answer 6

1. Lipid solubility (more lipid soluble = can cross lipid membrane easier)
2. Ionisation (unionised = more lipid soluble, ionised = less lipid soluble)
3. pH (when pKa value is similar to pH value, the drug will be unionised)

Question 7

What is volume of distribution?

Answer 7

Volume of fluid, where the drug would be uniformly distributed to produce observed conc. in blood.

Question 8

What is volume distribution used for?

Answer 8

• Index that tells you where the drug is in the body
• Determinant of half-life
• Calculate loading dose

Question 9

What is the role of liver in drug metabolism?

Answer 9

Provides blood supply

Drugs ingested through GIT will be inactivated in the liver, before entering systemic circulation.

Question 10

What are the types of drug metabolism?

Answer 10

1. Phase I reactions
2. Phase II reactions

Question 11

What are Phase I Reactions?

Answer 11

• Functional group is added or exposed
• Catalysed by cytochrome P450 mono-oxygenase system enzymes
• Results in loss of pharmalogical activity
• Form more lipophobic products

Question 12

What are Phase II Reactions?

Answer 12

• Covalent linkage is made between a functional group on a drug or Phase I metabolite
• Produce highly polar (lipophobic) molecules, excreted in urine

Question 13

What are the factors that affect drug metabolism?

Answer 13

• Interactions between drugs (some inhibit others altering metabolism)
• Disease status
• Hormonal status/gender
• Age
• Nutritional status
• Genetic factors (different response to the drug)

Question 14

What are prodrugs?

Answer 14

Drugs administered as inactive that are converted to active compounds in the body.
- maximum amount of active drug reaches target site
- converted by phase I reaction

Question 15

What is first-pass metabolism?

Answer 15

Drugs administered orally may be inactivated in liver or intestines before entering systemic circulation.

Can not be given orally if high does to specific target sites are needed.

Question 16

What is drug bioavailability?

Answer 16

Proportion of drug that passes into systemic circulation after oral administration.

Question 17

How is drug bioavailability measured?

Answer 17

• Amount absorbed from GIT
• Amount escaping extraction by liver (first-pass metabolism)

Question 18

What is total clearance?

Answer 18

The ability of an individual organ or the body to eliminate a drug.

Total body clearance = sum of all different clearance processes for a given drug

Question 19

What are the major routes of excretion?

Answer 19

• Urine
• Faeces
• Milk
• Sweat
• Expired air

Question 20

What is half-life?

Answer 20

Time taken for the amount of frug in the body to fall by half.

Increased by:
- increase in volume distribution
- decrease in clearance

Question 21

What is the duration of action?

Answer 21

The length of time the plasma drug conc. will stay within therapeutic range.

Question 22

What is dosing frequency?

Answer 22

How often the drug must be administered to be rapidly absorbed and have optimal results.