Drug Absorption

Question 1

To have biological action; what must a drug do in the body?

Answer 1

Enter the blood stream and be distributed at the site of action

Question 2

List the modes of administration

Hint: There are nine

Answer 2

Oral, Intravenous, Subcutaneous, Intramuscular, Sublingual, Rectal, Inhalation, Nasal, Transdermal

Question 3

The process of drug action can be broken into four steps - what are those steps?

Answer 3

Absorption, Distributionm Metabolism, Elimination

Question 4

Understanding the action of a drug enables us to understand what other processes?

Answer 4

Dosage, drug handling and administration, patient variability and the potential for harm

Question 5

What is the definition of drug absorption?

Answer 5

The process of movement of unchanged drug from the site of administration to the systemic circulation

Question 6

There is always a correlation between plasma concentration of a drug and the __________ _______ .

Answer 6

Therapeutic response

Question 7

What is the Tmax?

Answer 7

The time to peak concentration of a drug

Question 8

What is the Cmax?

Answer 8

The peak concentration a drug reaches in the blood

Question 9

What does the Area under the Curve of a drug concentration-time graph represent?

Answer 9

The amount of drug that reaches the systemic circulation

Question 10

Describe what is meant by therapeutic concentration

Answer 10

A drug is effective over a range of concentrations

Question 11

How is the therapeutic range measured?

Answer 11

Using the therapeutic index

Question 12

Describe what occurs if concentration of a drug falls outside of its therapeutic range

Answer 12

Above the range - toxicity

Below the range - insufficient/no pharmacological action

Question 13

What is bioavailability?

Answer 13

A mesure of the AUC which shows how much of the drug has been delivered to the systemic circulation and is available at the site of action

Question 14

Why percentage of bioavailability does a drug have that has been introduced intravenously?

Answer 14

100%

Question 15

List the factors effecting bioavailability

Answer 15

Formulation, ability to pass barriers, GI effects and first pass metabolism

Question 16

What is formulation?

Answer 16

The way the drug is designed - e.g. slow release preparations

Question 17

What factors effect a drugs ability to pass biological barriers?

Answer 17

Particle size, lipid solubility and pH due to ionisation

Question 18

What factos constitute the GI effect on drug absorption?

Answer 18

Gut motility, Presence of food and illness

Question 19

What is first pass metabolism?

Answer 19

Metabolism of a drug before its reached the systemic circulation

Question 20

How is first pass metabolism typically mechanised?

Answer 20

Enzymes

Question 21

What mode of administration is particularly effected by first pass metabolism ?

Answer 21

Oral route

Question 22

How does ionisation effect the permeability of drugs across barriers?

Answer 22

Ionised drugs cannot pass through membranes by diffusion

Question 23

How should ionised drugs behave? (Hint: Think about tonicity)

Answer 23

They should equilibrate in concentration across the membrane in order to not effect osmosis

Question 24

How is the degree of ionisation worked out?

Answer 24

Henderson-Hasselbalch Equation

Question 25

How is the lipid solubility of a species expressed?

Answer 25

A lipid-partition coefficient

Question 26

What is the lipid-partition coefficient?

Answer 26

The ratio of the amount of the drug which dissolves in the lipid and water phase when they are in contact

Question 27

A drug with a higher LPC will easily cross membranes. True or false?

Answer 27

True