Bioavalability

Question 1

Define bioavailability ‘F’

Answer 1

Fraction of a dose that reaches the systemic circulation unchanged

Question 2

Bioavailability via iv route, f =?

Answer 2

100%

Question 3

Bioavailability via enteral f =?

Answer 3

Depends, less than 100%

Question 4

Why is bioavailability for enteral use less than 100%?

Answer 4

Some drug will be lost through passage straight through GI tract
Pre-systemic metabolism (first pass or endothelial)
Drug and patient factors that affect absorption will also affect bioavailability

Question 5

F of caffeine

Answer 5

100%

Question 6

F of morphine?

Answer 6

25%

Question 7

F of sulfasalazine?

Answer 7

<15%

Question 8

Drug factors affecting bioavailability

Answer 8

Formulation of drug
Molecular size
Lipid solubility
Concentration

Question 9

Patient factors affecting bioavailability

Answer 9

Blood supply, absorption surface, gastric content bile, enteric bacteria, motility

Question 10

When drug comes of patent, other companies have to demonstrate that their drug is identical to the original. This can be shown how?

Answer 10

F relative

Question 11

Calculate F relative

Answer 11

Area under the curve oral drug 2 /area under the curve oral drug 1

Question 12

Calculate F absolute

Answer 12

Area under the curve oral/area under the curve iv