pharmacokinetics

Question 1

how to calculate therapeutic index

Answer 1

LD₅₀/ED₅₀

median lethal dose/median effective dose

Question 2

which is better- a therapeutic index of 1.5 or 4?

Answer 2

4 bigger is better with therapeutic index

Question 3

define efficacy

Answer 3

maximal effect of a drug

Question 4

define potency

Answer 4

the amount of a drug needed for an effect

Question 5

define pharmacokinetics

Answer 5

the mathematical description of how a drug’s plasma concentration changes over time

Question 6

How do you calculate bioavailability

Answer 6

F= AUC_oral/AUC_IV

determined by absorption- F= the fraction of the drug absorbed into the plasma

Question 7

what is the value of F always between?

Answer 7

0 and 1

where IV administration is 1, the oral fraction is AUC_oral/AUC_IV

Question 8

How do you calculate the oral dose of a medication

Answer 8

Dose_oral = Dose_IV/F

similarly Dose_{IV =} F x Doseoral

Question 9

what is D*_IV

Answer 9

Loading dose

Question 10

what is MD_IV

Answer 10

Maintenance dose

Question 11

how do you calculate concentration

Answer 11

C_o = D_IV / V_D

Question 12

what does ADME stand for?

Answer 12

Absorption

Distribution

Metabolism

Excretion

Question 13

zero- order pharmacokinetics

Answer 13

single compartment

fixed rate

concentration independent

Question 14

first-order pharmacokinetics

Answer 14

single compartment

variable rate

concentration dependent

Question 15

two compartement pharmacokinetic model

Answer 15

2 first order decays

2 variable rates

concentration dependent

Question 16

absolute vs relative units

Answer 16

Absolute = Relative x patient mass (kg)

Question 17

how do you calculate volume distribution

Answer 17

V_d = D_i.v./C_o

Question 18

what does a low V_d tell you

Answer 18

drug distributes to plasma

large molecules

charged molecules

excreted by kidney

t_1/2 usually short

Question 19

what does medium V_d tell you

Answer 19

small and hydrophilic

do not bind plasma proteins

extracellular- kidney excretion

intracellular- liver metabolism

Question 20

what does a large V_d tell you

Answer 20

concentrates in the tissues

small and lipophilic

bind to extravascular proteins or bone

t_1/2 usually long

Question 21

what determins half life: distribution phase or elimination phase?

Answer 21

elimination phase

Question 22

which drugs demonstrate zero-order decay

Answer 22

PEA

phenytoin

ethanol

aspirin

a pea looks like a 0

Question 23

michaelis-menton curve

Answer 23

shows mechanism for first-order kinetics

essentially linear

dependent on drug concentration

Question 24

define 1/2 life

Answer 24

used in 1st order decay

concentration decreases by 50% every half life

Question 25

how many half lives before concentration reaches 10%

Answer 25

**3.3** 1- 50% 2- 25% 3- 12.5% 4- 6.25%

Question 26

of half lives before complete elimination of a drug

Answer 26

5

Question 27

of half lives required to reach steady state in drug dosing

Answer 27

5

Question 28

how do you calculate the elimination constant (K_el)

Answer 28

0.7 / t_1/2

Question 29

how do you calculate the plasma clearance (Cl_p)

Answer 29

Cl_p = K_el x V_d