Drug Disposition III

Question 1

Important pharmacokinetic parameters: (5)

Answer 1

Bioavailability
Volume of distribution
First order elimination rate constant
Half-life
Clearance

Question 2

During time course of drug action, assume ____ concentrations are proportional concentrations at _____ tissue.

Answer 2

plasma

target

Question 3

Drug action models are especially useful when: (2)

Answer 3

• when magnitude of therapeutic effect cannot be measured clinically
• therapeutic window is narrow

Question 4

Pharmacokinetic parameters vary substantially in the population and can even change over time in a single patient. True or false?

Answer 4

true

Question 5

Most drugs are eliminated this way:

Answer 5

first order drug elimination

Question 6

Constant fraction of drug eliminated per unit time is ___ ____ drug elimination.

Answer 6

first order

Question 7

The first order elimination rate constant, ____ is the fractional rate of drug elimination.

Answer 7

k_E

Question 8

What are the units for k_E?

Answer 8

units of reciprocal time

Question 9

How do you calculate k_E given starting plasma concentration?

For example, starting plasma concentration is 600 ng/ml.

Answer 9

starting plasma concentration * (1-k_E)

480 ng/ml

Question 10

The time required to reduce the plasma drug concentration by 50% is known as _____.

What are the units?

Answer 10

half-life

time

Question 11

t_1/2 is _________ proportional to k_E.

Answer 11

inversely

Question 12

Estimate the half life of the drug:

Answer 12

50% of y-axis, then 1/2 on x-axis in left direction and half in right direction.

Subtract x(greater value) - x(lesser value) = seconds

about 0.7

Question 13

Calculate half life from Log Plasma Concentration versus time plot

t_{1/2 =}

Answer 13

-0.301/1

Question 14

What determines duration of action of a single dose?

Answer 14

half-life

Question 15

___-___ half-lives for a dose to be effectively eliminated

Answer 15

5-6

Question 16

In ______ dosage schedules, determines time to reach a new steady state when rate of administration changes.

Answer 16

chronic

Question 17

Together, half life with _____ __ _____, determines choice of dosage interval.

Answer 17

margin of safety

Question 18

Half life is an _____ process.

Answer 18

exponential

Question 19

Drug administration is ____ order and elimination is ____ order.

Answer 19

zero

first

Because taking the pill does not depend on plasma concentrations.

Question 20

What type of curve is this?

Answer 20

Plot of drug absorption and elimination

Elimination rate exceeds absorption so curve peaks

Question 21

Rate of drug absorption can be affected by: (3)

Answer 21

route of administration
blood flow
slow-release preparations

Question 22

Slower absorption means (2)

Answer 22

Lower peak concentrations
Longer duration of action

Question 23

______ plasma concentration is reached under:

• zero order drug administration
• first order drug elimination

Answer 23

Steady-state

Question 24

Most drugs given _____ every half life.

Answer 24

once

Question 25

\_\_\_\_ _____ , (units of \_\_\_) is the volume of plasma from which drug is fully removed per unit time.

Answer 25

plasma clearance ml/min

Question 26

CLp = Σ \_\_\_\_\_organs

Answer 26

CL of all

Question 27

CLp equation:

Answer 27

_rate of elimination_ plasma concentration

Question 28

KNOW What equation is this? C_SS \* CL_p Concentration of steady state \* clearance in plasma

Answer 28

Rate of Administration

Question 29

Half life has nothing to do with steady state. True or false? Clearance is 1.44 L/kg/h, and its half-life is 1.9 h. At what rate would you need to infuse morphine intravenously to achieve an effective steady state plasma concentration of 65 mcg/L in a 70 kg man?

Answer 29

true 6.5 mg/hr

Question 30

Clearance (CL) is __________ to half life.

Answer 30

inversely proportional

Question 31

CL is dependent on V_d. True or false?

Answer 31

false independent If your rate of Vd is increased, it is much slower to clear.

Question 32

It takes\_\_-\_\_\_ half-lives to reach steady- state.

Answer 32

5-6

Question 33

KNOW Time to reach new C_SS depends only on the \_\_\_

Answer 33

half life exponential

Question 34

What can occur if there is an altered clearance of drug, for example people with renal insufficiency?

Answer 34

cumulative poisoning

Question 35

Therapeutically it is better to reduce dosing rate because ____ \_\_\_\_ at steady state remains the same despite number of doses.

Answer 35

mean concentration

Question 36

Choice of dose interval depends on balance of the following: (4)

Answer 36

Drug half-life Size of therapeutic window Frequency/severity of adverse effects Convenience and patient compliance

Question 37

When is a loading dose needed? (2)

Answer 37

drugs with a long T rapid onset needed for emergency

Question 38

Total loading dose depends on: (3)

Answer 38

* plasma concentration * volume of distribution * bioavailability Total loading dose= [(concentration) (Vd)] / F Note: F is bioavailability

Question 39

Loading dose is ___ times maintenance dose.

Answer 39

2 like z pack

Question 40

Single loading dose followed by ______ maintenance doses.

Answer 40

smaller

Question 41

What is the major goals of drug monitoring and dose adjustment?

Answer 41

refine estimate of clearance refine estimate of bioavailability

Question 42

When do you sample when monitoring a drug? (2)

Answer 42

* Allow long enough after dosing for distribution phase to be over * Usually, best time is right before a scheduled dose

Question 43

When monitoring a drug it is important to know if the patient is in steady state with a drug. True or false?

Answer 43

true in order to get an accurate estimate of steady state

Question 44

Treat the patient, not just the number because: (2)

Answer 44

* Therapeutic window may vary with individuals * Knowledge of previous plasma concentrations is important

Question 45

Constant absolute amount of drug is eliminated per unit time is known as:

Answer 45

zero order kinetics of drug elimination

Question 46

Amount eliminated is independent of concentration of drug remaining at any given time is known as

Answer 46

zero order kinetics

Question 47

In zero order kinetics, it is possible to reach steady state. True or false?

Answer 47

false Can NEVER reach steady state!

Question 48

For oral or other routes, rate of administration equation is: What are the units?

Answer 48

_C_ss \* CL_p_ F mg/min Note: F is bioavailability, CL_p is plasma clearance