Bioavailability tutorial

Question 1

What are excipiants?

Answer 1

Other materials used in medicines that aren’t the drug itself

Question 2

What do excipiants do?

Answer 2

Improve its chemical or biological stability or to increase its acceptability to the patient by improving its flavour, fragrance or appearnace

Question 3

What is the process of making a medicine containing a drug called?

Answer 3

The formulation

Question 4

What are advantages of an oral route of administration of a medicine?

Answer 4

It permits self medication
It does not require rigorously sterile preparations
The incidence of anaphylactic shock is lower than IV
There is a capacity to prevent complete absorption eg vomiting or lavage

Question 5

What are disadvantages of an oral route of administration of a medicine?

Answer 5

They are inappropriate for drugs that:
- are liable in acid pH of stomach or otherwise degraded
- undergo extensive ‘first pass’ metabolism
It requires patient compliance

Question 6

What are the advantages of intravenously administrating a drug

Answer 6

Rapid onset of action

Avoids poor absorption from and the destruction within the GI tract

Question 7

What are the disadvantages of intravenously administrating a drug

Answer 7

Slow injection necessary to avoid toxic bolus
Higher incidence of anaphylactic shock
Trained personnel required
Complications possible eg embolism, phlebitis, pain

Question 8

What are the advantages of administrating a drug via inhalation

Answer 8

Ideal for small molecules, particles, gases, volatile liquids, aerosols
Enormous surface area presented by alveolar membranes
Simple diffusion, also phagocytic cells clear particles

Question 9

What are the disadvantages of administrating a drug via inhalation

Answer 9

Possible localised effect within the lung (unless this is desired)

Question 10

What are the advantages of intramuscularly administrating a drug

Answer 10

Relatively high blood flow, increased during exercise and enables depot therapy (prolonged absorption from pellet, microcrystalline suspension or solution in oily vehicle)

Question 11

What are the disadvantages of intramuscularly administrating a drug

Answer 11

Possible infection and nerve damage, especially in gluteal region

Question 12

What are the advantages of subcutaneously administrating a drug

Answer 12

Local administration, dissemination can be minimised for local effect
Enables depot therapy

Question 13

What are the disadvantages of subcutanously administrating a drug

Answer 13

Pain
Abscess
Tissue necrosis

Question 14

What are the advantages of percutaneously administrating a drug

Answer 14

Local application and action

Lipid soluble compounds diffuse rapidly (may be assisted by vehicles)

Question 15

What are the disadvantages of percutaneously administrating a drug

Answer 15

Local irritation and skin reactions

Alterations of skin structure eg steroids lead to subcutaneous adipose tissue

Question 16

Why are excipients added to a drug formulation?

Answer 16

Flavourings, colourings, things to make it a solid or liquid, stabilizer?, in order to make the drug big enough to hold - to provide bulk, improve absorption (performance), capsule is to protect drug from low ph in stomach so can affect lower down

Question 17

What are examples of agents that can be used as excipients

Answer 17

Inorganic materials eg chalk, talc, glucose, lactose, a counter ion for the drug which can make it taste better by making salt

solvents like water, alcohol or oil

Question 18

What is bioavailability?

Answer 18

amount of a drug contained in a medicine that enters the systemic circulation in an unchanged form after administration of the product

Question 19

Why is it important for a drug to be bioavailable

Answer 19

So it can react in the desired way to treat the patient. If the conc that reaches the desired place isn’t high enough then the drug won’t be effective

Question 20

Does the measurement of bioavailability always reflect the effectiveness of a drug?

Answer 20

No, as some medicines like creams don’t need to travel systemically. These already reach the target organ before entering the body - similarly respiratory conditions can be treated like this. Also pro drugs have low bioavailability as activated within the body

Question 21

What factors influence bioavailabiity

Answer 21

1. the physicochemical characteristics of the drug (ionisation in gut)
2. gastrointestinal pH
3. whether or not the drug is passively or actively transported
4. gastrointestinal motility
5. particle size of the drug
6. physicochemical interaction between drug and gut contents (e.g. chemical interaction between calcium and tetracycline antibiotics)

Question 22

What are the different ways aspirin can be administrated?

Answer 22

aspirin tablets B.P. – ordinary aspirin tablets sold in chemists
soluble aspirin – these are dissolved in water and the solution swallowed
enteric-coated aspirin – these have a sugar and wax coating which remains intact in dilute acid but quickly dissolves in alkali

Question 23

What is the bioequivalence of a drug?

Answer 23

Evidence that the new ‘generic’ product behaves sufficiently similar to the existing one

Question 24

How can drugs be metabolised to inactive products?

Answer 24

the microbes within the gut lumen
enzymes present in the gut wall
enzymes in the liver