Tutorial: Bioavailibility

Question 1

What is pharmacology?

Answer 1

It it the science of chemicals that potentially could benefit patietns

Question 2

What is the difference between a drug and a medicine?

Answer 2

A drug is the chemical which should have its effect

A medicine is a dosage form of the drug but also contains excipients (zusätze)

Question 3

What is the functio of exipents in a medicine?

Answer 3

• to improve its chemical and biological stability
• to increase its acceptability to the patient by improving its flavour, fragrance or appearance
• To make it able to grab e.g. the pill (increase size)
• to increase its bioavilibility

Question 4

What involves the process called formulation?

Answer 4

The process of making a medicine (with excipients) containing a drug

Question 5

What are the advantages and disadvantages of oral administration of a medicine?

Answer 5

Advantage

• It permits self-medication
• It does not require rigorously sterile preparations
• The incidence of anaphylactic shock is lower (than intravenous)
• There is the capacity to prevent complete absorption (vomiting, lavage).

Disadvantage

It is inappropriate for drugs which:

• are labile in acid pH of stomach or otherwise degraded
• or undergo extensive ‘first-pass’ metabolism,

It requires patient compliance.

Question 6

What are the advantages and disadvantages of IV administration of drugs?

Answer 6

Advantage

• rapid onset of action
• avoids poor absorption from, and destruction within, the g.i. tract permits careful control of blood levels

Disadvantages

• slow injection necessary (to avoid toxic bolus) higher incidence of anaphylactic shock
• trained personnel required
• complications possible; embolism, phlebitis, pai

Question 7

What are the advantages and disadvantages of inhalation/ administration of a drug via the lungs?

Answer 7

Advantages

• ideal for small molecules, particles, gases, volatile liquids, aerosols
• enormous surface area presented by alveolar membranes
• simple diffusion, also phagocytic cells clear particles

Disadvantages

• possible localised effect within lung (unless this is desired)

Question 8

What are the advantages and disadvanatages of IM administration of a drug?

Answer 8

Advantages

• relatively high blood flow, increased during exercise enables DEPOT THERAPY (prolonged absorption from pellet, microcrystalline suspension or solution in oily vehicle).

Disadvantages

• possible infection and nerve damage (especially in gluteal region)

Question 9

What are the advantages and disadvantages of a subcutaneous administratio of a drug?

Answer 9

Advantages

• Local administration, dissemination can be minimised for local effect
• enables DEPOT THERAPY (as for intramuscular above)

Disadvantages

• pain, abscess, tissue necrosis

Question 10

What are the advantages and disadvantages of percutaneous (across the skin) administration of a drug?

Answer 10

Advantages

• local application and action
• lipid soluble compounds diffuse rapidly (may be assisted by vehicles)

Disadvantages

• local irritation and skin reactions
• alteration of skin structure (e.g. steroids – subcutaneous adipose tissue)

Question 11

What is bioavailibility?

Answer 11

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

Question 12

How do each of the following influene bioavailibitly of a drug?

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)

Answer 12

• the physicochemical characteristics of the drug (ionisation in gut)
• gastrointestinal pH

–> diffusion of ver membrane

• whether or not the drug is passively or actively transported

–> might rely on transport mechanisms (can be genetically different)

• gastrointestinal motility
• particle size of the drug

–> Smaller Particle, higher motility= more/faster absorbtion

physicochemical interaction between drug and gut contents (e.g. chemical interaction between calcium and tetracycline antibiotics)

Question 13

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

Answer 13

No, some durgs can be effective without having a high bioavailability

Also, some drugs have to be metabolised to be effective –> would potentially have low bioavilibilty (because of its definition)

Question 14

What is the therapeutic index/therapeutic window?

Answer 14

The range of mount of drug that can be administered between

• Lower end: its usefullness
• Upper end: its toxicity

Question 15

Name examples of how a drug can be altered in the presystemic metabolism/ first pass metabolism)

Answer 15

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

Question 16

Under what circumstances could a drug, which undergoes 100% first pass metabolism, be therapeutically useful?

Answer 16

Either

• target side is berfore first pass site (e.g. Intestinal target after oral use)
• administration without going to liver (e.g. iv, sublingual)
• Metabolism required to make drug usefull

Question 17

What is bioequivalence?

Answer 17

evidence that the new ‘generic’ product behaves sufficiently similar to the existing one to be substituted for it without causing clinical problems

–> otherwie coule be different e.g. because of excipients