Drug Disposition - Lecture 2

Question 1

What are the fates of drug in the body?

Answer 1

Absorption
Distribution
Metabolism
Excretion

Question 2

What two process combine together to create the process of Drug Elimination?

Answer 2

Metabolism and Excretion

Question 3

What is absorption of a drug dependent upon?

Answer 3

Solubility
Chemical Stability
Lipid to water partition coefficient

Question 4

What quality must a drug have to be soluble to a cell?

Answer 4

It must have a degree of lipid solubility

Question 5

What affects the rate at which a drug is absorbed?

Answer 5

The Lipid to water partition coefficient

Question 6

What does a high Lipid to water partition coefficient mean?

Answer 6

Easily soluble with cells and can be absorbed

Question 7

What does a low Lipid to water partition coefficient mean?

Answer 7

Not easily soluble in a cell. Difficulty being absorbed

Question 8

What does Ka represent ?

Answer 8

The ratio of the drug that has been ionised

Question 9

What does pKa show?

Answer 9

pH at which 50% of drug is ionised and 50% unionised

Question 10

Is an acidic drug more ionised in an acidic environment or a basic environment?

Answer 10

Basic

Question 11

Is an basic drug more ionised in an acidic environment or a basic environment?

Answer 11

Acidic

Question 12

What is Systemic Availability?

Answer 12

Systsemic Availability = Amount in Systemic Circulation/Amount absorbed

Question 13

What is first-pass or presystemic metabolism?

Answer 13

This is were a drug once absorbed can be inactivated by enzymes in the gut wall and the liver before reaching the systemic circulation

Question 14

What are the routes of drug adminisation?

Answer 14

Oral
Inhalation
Buccal
Sublingual 
Transdermal
Subcutaneous 
Rectal
Intramuscular

Question 15

What are the advantages of the Oral route administration?

Answer 15

• Convenient
• Non-sterile route
• Good absorption for most

drugs

Question 16

What are the disadvantages of Oral route administration?

Answer 16

• First pass metabolism
• Variable absorption
• GI irritation

Question 17

What is the Buccal route/Sublingual route of administration?

Answer 17

Under the tongue

Question 18

What are the advantages of Buccal administration?

Answer 18

• By passes the portal system and avoids first pass metabolism
• Avoids gastric acid

Question 19

What are the disadvantages of Buccal administration?

Answer 19

• Few sub-lingual drugs

Question 20

What are the advantages of Rectral administraiton?

Answer 20

• Avoids First pass metabolism

- Used for nocturnal administration

Question 21

What are the disadvantages of Rectal administration?

Answer 21

-Aesthetically unacceptable

Question 22

What are the advantages of Intravenous administration?

Answer 22

Rapid onset

Continuous infusion

Question 23

What are the disadvantages of Intravenous administration?

Answer 23

Sterile preparation required

Risk of sepsis or embolism

High drug levels at the heart

Question 24

What are the advantages of Intramuscular administration?

Answer 24

Rapid onset of lipid soluble drugs

Slow prolonged release

Question 25

What are the disadvantages of Intramuscular administration?

Answer 25

Painful Tissue damage with some drugs

Question 26

What are the two forms a drug can exist in when in a fluid compartment?

Answer 26

Bound forms Free forms (Only free drugs are able to move compartments)

Question 27

In terms of charge, what type of drug can move readily by diffusion?

Answer 27

Unionised drugs

Question 28

What are the fluid filled compartments of the body?

Answer 28

``` Plasma water Interstitial water Intracellular water Transcelluar water Fat ```

Question 29

What does Transcellular water consist of?

Answer 29

Cerebral Spinal Fluid Synvoial fluid Fluid in the eye

Question 30

How is Volume of Distribution indicate?

Answer 30

Vd(Volume) = Dose(Mass) ---------------------- Plasma Concentration

Question 31

What is the Volume of Distribution?

Answer 31

Volume of Distribution is the apparent volume in which a drug is dissolved?

Question 32

What does a Vd<5 L imply?

Answer 32

Implies the drug is retained within the vascular compartment

Question 33

What does Vd < 15L imply?

Answer 33

Suggests that the drug is restricted to the extracellular fluid

Question 34

What does a Vd > 15 L

Answer 34

Indicates distribution throughout the total body