Bioavailability and Bioequivalence

Question 1

Define bioavailability

Answer 1

The fraction of the dose which reaches the systemic circulation intact.

IV bioavailability by definition is 100%

Question 2

How is bioavailability measured

Answer 2

Using the area under the concentration-time curve (Dost’s Law).

AUC oral = Bioavailability
________
AUC IV

Question 3

What is relative vs absolute bioavailability

Answer 3

Absolute bioavailability compares non-IV route with IV administration

Relative bioavailability compares non-IV administration with another defined route of administration

Question 4

What is bioequivalence

Answer 4

If the active ingredient from both drug formulations achieves the same concentration at the same rate, then the drugs will likely achieve the same clinical effect, and so they can be considered bioequivalent

AUC drug A
________
AUC drub B

if this ratio is between 0.8 to 1.25 –> the company can claim that the two formulations are bioequivalent

Question 5

Define Clearance vs. drug elimination rate

Answer 5

Clearance is the volume of blood that is completely cleared of a drug per unit time.

Drug elimination rate is the amount of drug cleared from the blood per unit time

Question 6

What is Mean Residence TIme and how is it calculated

Answer 6

MRT is a measure of how long the drug stays in the body and is similar to a time constant in the compartment models