Drug Elimination and Dosing

Question 1

what the body does to the drug

Answer 1

pharmacokinetics

Question 2

what the drug does to the body

Answer 2

pharmacodynamics

Question 3

the central dogma states that the plasma concentration of a drug (Cp) determines ________

Answer 3

the drug’s clinical effects

Question 4

this way of administering drug has no lag time (goes directly into bloodstream)

Answer 4

IV administration

Question 5

what determines the loading dose (LD)

Answer 5

volume of distribution (Vd)

Question 6

what determines the maintenance dose-rate (MD)

Answer 6

clearance (CL)

Question 7

the time during which plasma concentration becomes half of the initial concentration

Answer 7

half-life (t1/2)

Question 8

what determines the time to steady state and the dosing interval

Answer 8

half-life (t1/2)

Question 9

what happens when a drug is eliminated from the body at a fast rate

Answer 9

have to administer that drug more often

Question 10

volume of plasma cleared of drug in unit time

Answer 10

Clearance (CL)

Question 11

2 main ways a drug is eliminated:

Answer 11

excretion (renal)
metabolism (hepatic)

Question 12

measures the proportion of red blood cells in the blood

Answer 12

hematocrit

Question 13

only applies to drugs w/ first-order kinetics (most drugs)

Answer 13

Clearance (CL)

Question 14

CL=

Answer 14

elimination rate/Cp

Question 15

this order of kinetics is directly proportional to the plasma concentration of drug; deals with exponential decay

Answer 15

First-Order Kinetics

Question 16

Cp=

Answer 16

D/Vd

D-dose
Vd-volume of distribution

Question 17

elimination rate constant (k)=

Answer 17

CL/Vd

Question 18

t1/2=

Answer 18

(0.7 x Vd)/CL

Question 19

this type of elimination does not care how much concentration you have, the same amount is being eliminated per unit of time

Answer 19

zero order elimination

Question 20

the 3 drugs that use zero-order elimination

Answer 20

Phenytoin, Ethanol, Aspirin (PEA)

Question 21

k0=

Answer 21

• (change in Cp)/t

Question 22

logarithmic Y axis means what kind of elimination

Answer 22

first order

Question 23

linear Y axis means what kind of elimination

Answer 23

zero order

Question 24

t1/2 (for zero order)=

Answer 24

1/2 Cp0 (initial drug conc.)/k0

Question 25

solution for waiting for 4-6 half-lives to achieve effective concentration in plasma

Answer 25

give loading dose

Question 26

solution for effective concentration that cannot be maintained

Answer 26

give maintenance dose

Question 27

for intravenous drugs, what is always 1 or 100%

Answer 27

F (bioavailability of drug)

Question 28

a larger one-time dose to get patient up to the desired plasma concentration w/out having to wait for 4-6 half-lives

Answer 28

loading dose

Question 29

LD=

Answer 29

(Cp x Vd)/F

Question 30

MD=

Answer 30

(Cp x CL)/F

Question 31

the dose at which the elimination of drug= rate of administration

Answer 31

MD

Question 32

F=

Answer 32

area of PO curve/area of IV curve

Question 33

fraction (F) of an orally administered dose that reaches the systemic circulation

Answer 33

bioavailability

Question 34

creatinine drug clearance formula:

Answer 34

CL=(urine flow x drug conc. in urine)/Cp

Question 35

this is used if 24 hour urine can't be collected

Answer 35

Cockcroft-Gault

Question 36

Cockcroft-Gault formula:

Answer 36

CL= [body weight x (140-age)]/[72 x Cr serum conc.]