Drug Administration and Absorption

Question 1

What needs to be considered when choosing a route of administration for a drug

Answer 1

• physiochemical properties of the drug
• molecular size
• where its target site of action is located due to varying difficulty of entrance for different sites
• its bioavailability
• convenience of taking drugs

Question 2

Bioavailability

Answer 2

This refers to the amount of free drug that is able to reach its target site and how much of the drug will be metabolized before it can reach its target site

Question 3

Possible routes of administration

Answer 3

-Enteral: Goes through GI tract
Parenteral: Does not pass through GI tract

Question 4

Intended circulation of drug

Answer 4

Topical/ Local: stays at site of administration
Systemic: circulates through the body

Question 5

Different types of Drug administration

Answer 5

pulmonary epithelium
injection
Intramuscular injection
intravenous injection

Question 6

List the advantages and disadvantages of topical administration

Answer 6

Advantages:
Rapid onset of action
Convenient
no first pass degradation
decrease adverse effect

Disadvantages:
limited to small volume
may be impractical to administer

Question 7

Transdermal (percutaneous)

Answer 7

Drug absorption into systemic circulation (the patch)

Question 8

Advantages/Disadvantages of the patch

Answer 8

Advantages:
- rapid onset of action
- bypasses first pass degradation
3 L’s :lipophilic, low dose, low molecular weight

Disadvantages:
Depends on the drug property
skin irritation

Question 9

Oral Mucosa

Answer 9

• Placing the drug underneath the tongue for absorption

Advantages:
Rapid onset of action
bipass first pass degradation

Disadvantages:
limited to small drugs that can penetrate oral mucosa
may not be efficient for large doses

Question 10

Why would an enema be useful

Answer 10

This is useful for when oral is not an option

Question 12

Why are some drugs taken with/without food

Answer 12

The food can act as a protection against the drug getting degraded.

It can increase/decrease bioavavilability

Question 13

What creations have been made to combat first pass degradation in GI tract

Answer 13

Enteric coating, however less may be absorbed

Extended/Controlled release: slow uniform dissolution

Question 14

For IV, what different types of injections are there

Answer 14

Bolus injection: several circuits of administration

Slow infusion: allows drug concentration to be titrated so you can maintain constant drug levels over time

Question 15

How do you decide which is best route of administration

Answer 15

1. therapeutic objectives
2. drug properties
3. Setting and patient related factors

Question 16

Different mechanisms of absorption

Answer 16

Passive, Active, Facilited

Question 17

What will be absorbed by passive transport

Answer 17

small, polar molecules that will be absorbed by aquaporin channels from high to low concentration

Question 18

What does the rate of lipid diffusion depend on?

Answer 18

Drug concentration
degree of ionization
Pow (how lipid soluble)
Surface area of membrane

Question 19

Rate of permeation _____ with drug concentration

Answer 19

increase due need to re-equilibrate

Question 20

Partition Co-efficient

Answer 20

This is a measure of the concentration of lipid soluble/water soluble in drugs to determine how soluble a drug will be in cell membranes

Question 21

What causes the cut off phenomenon

Answer 21

Due to the unstirred water layer, the more drug that you have that is lipid soluble, will eventually have enough difficulty crossing this water layer to decrease the Pow

Question 22

The degree of ionization

Answer 22

only unionized drugs can pass the barrier and it will depend on the pka of the drug and pH of the organ compartment

Question 23

the surface area of the compartment

Answer 23

the higher the surface area of the compartment, ie the intestines, the more potential area or surface the drug will have to permeate

Question 24

Facilitated diffusion

Answer 24

Diffusion for larger molecules that may not be ATP driven but it will involve carrying drugs up/down a gradient

Question 25

why do drugs that undergo facilitated diffusion become saturated

Answer 25

Because there is only a certain amount of room available for drugs to lock in to so they can be carried.

Question 26

What do transport proteins do?

Answer 26

They assist larger proteins get to where they need to go and can increase the drug distribution and absorption