[3] Bioavailability

Question 1

Formula for amount of drug absorbed reaching the plasma

Answer 1

F x Dose

Question 2

Example:

F of Digoxin is 0.7
For Digoxin 250 ug preparation

How much is absorbed in oral?
How much is absorbed through IV?

Answer 2

Oral: 0.7 * 250 = 175 ug

IV: 250 ug

Question 3

Definition: Area Under the Blood Concentration Curve (AUC)

Answer 3

Common measure of the extent of Bioavailability

Question 4

Absolute Bioavailability is equal to?

Answer 4

F, the fraction of the dose that is Bioavailable

Question 5

For drugs given intravascularly, what is F?

Answer 5

F = 1

Drug is completely absorbed

Question 6

Formula: Absolute Bioavailability

Answer 6

[(AUC) PO / Dose PO] / [(AUC) IV / Dose IV]

Question 7

Define: Relative Bioavailability

Answer 7

Bioavailability of a drug as compared to a recognized standard

Question 8

Formula: Relative Bioavailability

Answer 8

(AUC) A / (AUC) B

Where drug product B is the recognized reference standard

Question 9

[Question]

Oral F is 50%
Standard IV Dose is 50 mg

What should the ORAL dose be if the goal is to reach the same plasma drug concentration?

Answer 9

100mg

Question 10

Define: First Pass Effect

Answer 10

Decreases the amount of active drug reaching the systemic circulation

Question 11

Why is Lidocaine given intravenously?

Answer 11

Extensive first pass effect so oral doses would be extremely large

Question 12

Rate of Absorption is measured by?

Answer 12

Tmax

Question 13

What is considered one of the most successful pieces of legislation ever passed?

Answer 13

Hatch-Waxman Amendments to FFD&C Act of 1984

Question 14

Is bioequivalence the same as therapeutic equivalent?

Answer 14

They are EXPECTED to be

Question 15

Why is only Cmax and AUC the really important to determine Bioequivalence?

Answer 15

Assuming these are similar, there is no reason that other factors (Vd, C, etc.) should be any different

Question 16

How similar must the Cmax and AUC be of different drugs to be considered Bioequivalent?

Answer 16

90% CI must fit between 80-125%

Question 17

[T/F] Given a graph of two drugs that look like they have the same CMax and AUC can you say they are Bioequivalent?

Answer 17

Cannot do it by eyeballing, must calculate

Question 18

If a drug is not bioequivalent, is it a bad drug?

Answer 18

Not necessarily, it just cannot be said to be the generic version of the drug it is copying

Question 19

[T/F] Bioequivalent drugs are always good drugs

Answer 19

F

It depends on the quality and other factors involved in the making of the drug