E1 L6: Bioavailability and Clearance 1

Question 1

Fraction of the administered dose that reaches systemic circulation (the heart)

Answer 1

Bioavailability

Question 2

The value of F is termed

Answer 2

Relative bioavailability

Question 3

Bioavailability units and range

Answer 3

No units
Varies between 0-1

Question 4

Reflects the total amount of drug the body is exposed to
The larger, the more drug the body is exposed to

Answer 4

AUC

Question 5

F usually indicates bioavailability of

Answer 5

Oral dosage form

Question 6

The fraction of oral dose that reaches systemic circulation

Answer 6

F (AUCpo/Dosepo)/(AUCIV/DoseIV)

Question 7

Fraction of drug absorbed

Answer 7

Fa

Question 8

Fraction of drug that has survived gut metabolism

Answer 8

Fg

Question 9

Fraction of drug that has survived hepatic metabolsim

Answer 9

Fh

Question 10

Estimation of F requires

Answer 10

Both oral and IV data

Question 11

Determinants of F

Answer 11

Intestinal absorption
Intestinal metabolism (insignificant for most drugs)
Hepatic metabolism

Question 12

Low bioavailability is due to

Answer 12

Poor intestinal absorption and or high hepatic metabolism during the first pass through the liver

Question 13

How much of drug is gone when it goes through liver

Answer 13

90%

Question 14

Q: T/F: Drugs that are poorly absorbed from the intestine are expected to show low F values

Answer 14

True - show low bioavailability

Question 15

Q: T/F: Drugs that experience significant first pass effect are expected to have low F values

Answer 15

True

Question 16

The proportionality constant relating the rate of drug elimination and the plasma concentration

Answer 16

Clearance

Question 17

Elimination =

Answer 17

Hepatic clearance + Renal Clearance

Question 18

Urinary excretion accounts for - of total drug elimation

Answer 18

20%

Question 19

Systemic blood clearance, total blood clearance, blood clearance

Answer 19

CLb

Question 20

If all drug molecules are distributed in the plasma

Answer 20

Drug amount in plasma = drug amount in blood

Question 21

If a drug does not bind to blood cells, blood/plasma concentration ratio is

Answer 21

0.50.6

Question 22

Certain drugs such as - and - distribute into RBC significantly, having a blood/plasma conc. ratio greater than 15

Answer 22

Tacrolimus and cyclosporine

Question 23

Q: T/F: When a drug is distributed mainly in the plasma, Vd estimated from blood concentration is larger than that from plasma concentration

Answer 23

True - IV bolus kinetic, distribution is drug specific; in most cases we measure conc in plasma; most measurements based on plasma samples

Question 24

The proportionality constant relating the rate of drug elimination and drug concentration in plasma

Answer 24

CL

Question 25

The proportionality constant relating the rate of drug elimination and the drug concentration in blood

Answer 25

CLb

Question 26

T/F: CLb can be estimated from CL and blood/plasma drug concentration ratio (Cb/Cp)

Answer 26

True

Question 27

For drugs mainly distributed into plasma Cb/Cp =0.5; That means

Answer 27

CLb = 2*CL

Question 28

If a drug is mainly distributed in plasma AUCblood =

Answer 28

1/2 of AUCplasma

Question 29

T/F: After oral admin of 1g drug, you obtain plasma drug concentration vs time. You can estimate AUC from the curve. Using the data, you can calculate CL

Answer 29

False- clearance tells about the rate of drug elimination

Question 30

T/F: CL is a PK parameter reflecting the rate of drug elimination

Answer 30

True

Question 31

T/F: CL is smaller for drugs that are eliminated faster

Answer 31

False - larger

Question 32

T/F: After IV, faster drug elimination leads to smaller AUC and larger CL values

Answer 32

True

Question 33

T/F: After po, AUC reflects “absorption” as well as elimination

Answer 33

True