Pharmacokinetics II

Question 1

What is the equation for the volume of distribution of a drug?

Answer 1

Amt of drug in body / C : C=concentration

Question 2

How can you tell how much of the drug is within the vasculature?

Answer 2

compare the volume of the drug, with the volume of blood.

Question 3

What is the formula for clearance?

Answer 3

rate of elimination / C

Question 4

What is zero-order elimination?

Answer 4

Rate of elimination is independent of drug concentration

Question 5

What is first-order elimination?

Answer 5

Elimination of a constant fraction of a drug

Question 6

What is capacity-limited elimination?

Answer 6

Body has a saturable rate of elimination.

Question 7

What is flow dependent elimination?

Answer 7

The capacity of the body to eliminate is dependent on the flow of blood to the liver/kidneys

Question 8

What is a half-life?

Answer 8

The time it takes for the concentration of a drug in the plasma to decrease by 50%, expressed in units of time

Question 9

What is the equation for half life?

Answer 9

= 0.693*V / CL

Question 10

How many half-lives are needed to eliminate a drug?

Answer 10

4-5

Question 11

Why can you not extrapolate the rate of drug [c] in a two compartment model?

Answer 11

You’d ignore the distribution that takes place

Question 12

Accumulation of a drug will begin to occur, if you dose shorter than how many half-lives?

Answer 12

4

Question 13

What is the accumulation factor?

Answer 13

1/ fraction lost in one dosing interval

Question 14

What is bioavailability?

Answer 14

The amount of drug that reaches the systemic circulation.

Question 15

How do you calculate the bioavailability of a drug, given some f(x)?

Answer 15

Integrate

Question 16

Bioavailability is influenced by what two factors?

Answer 16

Rate and extent of absorption

Question 17

What is the extraction ratio?

Answer 17

The effect of first pass metabolism which will impact the extent to which a drug will reach the circulation

Question 18

What is the equation for the extraction ratio?

Answer 18

ER = Cl(liver) / Q : Q= hepatic blood flow

Question 19

What is the equation for the bioavailability of a drug, F?

Answer 19

F = f*(1-ER) : f = extent of gut absorption

Question 20

What is the equation for the steady state concentration?

Answer 20

Dosing rate / CL

Question 21

What is the steady state concentration?

Answer 21

The point during a dosing regimen, when elimination of a drug, is equal to the bioavailability of the drug

Question 22

How many half lives does it take to reach a steady state concentration?

Answer 22

4-5

Question 23

What is a maintenance dose?

Answer 23

Dose needed to maintain a steady state concentration, and enough drug is administered to replace the amount of drug lost in the proceeding dose

Question 24

What is the equation for the dosing rate via IV?

Answer 24

CL * TC

Question 25

What is the equation for the dosing rate (oral)?

Answer 25

Dosing rate / Foral

Question 26

What is the equation for the maintenance dose?

Answer 26

Dosing rate * dosing interval

Question 27

Why is a smaller dosing interval important?

Answer 27

Will lead to a narrower range of [drug]

Question 28

What is the equation for the loading dose?

Answer 28

V*TC / F

Question 29

Do the problem at the end of the slideset