Clinical Applications of Pharmacokinetics

Question 1

Clearance

Answer 1

Cl= rate of elimination/C

Question 2

Slope of the Log C vs T relationship is…

Answer 2

Inverse of Half-life! Steeper slope, shorter half life

Question 3

Vd equation

Answer 3

Vd=A/C

Question 4

T1/2 Equation

Answer 4

T1/2 = (.7xVd)/Cl

Question 5

Vd after distribution is complete

Answer 5

Vd extrap = A / C0extrap

Question 6

Does a higher concentration of free drug increase or decrease Vd?

Answer 6

Increases Vd! More available to move into tissues. This also increases the half life.

Question 7

Css

Answer 7

Steady state concentration that occurs when a drug is infused. This is assuming that nothing happens to change the clearance of the drug.

Question 8

At Css, rate of infusion = _________ .

Answer 8

Rate of elimination.

Question 9

Equation for Css

Answer 9

Css=IR/Cl

Question 10

Does Vd affect css?

Answer 10

No, but a drug with a higher Vd will take longer to reach Css.

Question 11

How long does it take to reach Css?

Answer 11

Generally about 4-5 half lives.

Question 12

How long does it take to get from one Css to a new one?

Answer 12

4-5 more half lives. New Css is reached when infusion rate is increased.

Question 13

How to reach Css without waiting 4-5 half lives?

Answer 13

Loading dose!

Question 14

Correct loading dose equation

Answer 14

Dl = Css * Vd

Question 15

What else do we need to consider for oral administration of a drug?

Answer 15

Bioavailability and rate of absorption

Question 16

How to determine bioavailability (F)?

Answer 16

Compare AUC oral vs AUC IV.

Question 17

Amount of drug entering body after oral administration?

Answer 17

A=Dose * F

Question 18

Clearance equation w/bioavailability

Answer 18

Cl = (D*F)/ AUCoral

Question 19

Slow absorption effect on Cmax and T max

Answer 19

Decreases Cmax, increases Tmax

Question 20

What happens to rate of elimination of average concentration rises?

Answer 20

Rate of elimination increases

Question 21

Does it take more time to remove all of a drug from a previous dose during repeated administration or a single dose?

Answer 21

Single dose

Question 22

Cssav equation

Answer 22

DF/TCl

Where T is the interval between doses.

Question 23

Does slower oral absorption result in larger or smaller peaks and troughs?

Answer 23

Smaller - more even activation.