Pharmacokinetics ADME

Question 1

What does ADME stand for and what does it mean?

Answer 1

A=Absorption
D=Distribution
M=Metabolism
E=Elimination
AD are drug in
ME are drug out
ADME are the four bodily processes involved when a drug is taken

Question 2

What are the routes of drug administration? (Oi! it is sir! and classifications)

Answer 2

Enteral = Delivery of drug into internal environment of body through GI tract
Parenteral = Delivery of drug by all other routes
Oi! It is sir:

Oral (Enteral)
Intravenous (Parenteral)

Intramuscular (Parenteral)
Transdermal(Parenteral)

Inhalation (Parenteral)
Sublingual (Enteral)

Subcutaneous (Parenteral)
Intranasal (Parenteral)
Rectal (Enteral)

Question 3

Pros and cons of Oral administration

Answer 3

ORAL
Safe, easy, cheap
Limited absorption, affected by food intake

Question 4

Pros and cons of Intravenous administration

Answer 4

INTRAVENOUS
Immediately effective – good for emergencies
Aseptic techniques required

Question 5

Pros and cons of Intramuscular administration

Answer 5

INTRAMUSCULAR
Good for self-administration (diabetes)
Painful

Question 6

Pros and cons of Transdermal administration

Answer 6

TRANSDERMAL
Painless, works well with lipophilic drugs
Can cause allergic reactions, delayed delivery

Question 7

Pros and cons of Inhalation administration

Answer 7

INHALATION
Rapid absorption, good for self-administration
Addictive route, hard to regulate

Question 8

Pros and cons of Sublingual administration

Answer 8

SUBLINGUAL
Avoids first pass effect
Tooth discolouration

Question 9

Pros and cons of Subcutaneous administration

Answer 9

SUBCUTANEOUS
Good for slow release
Painful

Question 10

Pros and cons of Intranasal administration

Answer 10

INTRANASAL
Rapid absorption
Hydrophilic drugs have low permeability

Question 11

Pros and cons of Rectal administration

Answer 11

RECTAL
Bypasses first-pass effect and stomach acid
Irritation, unpleasant for patient

Question 12

How are drugs absorbed by the body? Give examples

Answer 12

Passive diffusion
- Lipophilic drugs e.g. Steroids
- Protonated weak acids e.g. Valproate anti-epileptic
- Deprotonated weak bases
Facilitated diffusion
Co-transport
- Prozac antidepressant couples with Na+

Question 13

What factors affect drug absorption?

Answer 13

Physiochemical
- Length and SA of small intestine
- how many transport proteins there are in the GI
Physiological
- blood flow
- food eaten
First pass effect

Question 14

What is the First Pass effect?

Answer 14

Drug must pass through GI system before it reaches blood
As it passes through different regions, drug may be denatured by enzymes
e.g. phase 1 & 2 enzymes in liver
Proportion of drug is lost, which affects its therapeutic potential

Question 15

What is bioavailability and how is it calculated?

Answer 15

Describes the concentration of a drug in systemic blood in relation to the dose given
f = amount in systemic circulation/ total dose given
Intravenous ALWAYS has 100% bioavailability

Question 16

What is drug distribution?

Answer 16

How drugs journey through the blood to their target tissues

Question 17

What factors affect drug distribution? (4)

Answer 17

1) Drug transmembrane proteins
2) Blood and tissue pH
3) Drug binding to blood/tissue protein
4) Water/fat in body

Question 18

What is apparent volume of distribution?

Answer 18

A summary measure of drug movement from plasma into target tissue

• The smaller the value, the less the penetration of the interstitial/intracellular fluids
• The greater the value, the greater the penetration of the fluids

Question 19

How is volume of distribution calculated? What are the units?

Answer 19

Vd = drug dose/ concentration of drug in plasma

standard: L (average 70kg man)
specific: L/kg (dependent on individual’s weight)