# Drug Disposition III Flashcards

1
Q

Important pharmacokinetic parameters: (5)

A

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

2
Q

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

A

plasma

target

3
Q

Drug action models are especially useful when: (2)

A
• when magnitude of therapeutic effect cannot be measured clinically
• therapeutic window is narrow
4
Q

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

A

true

5
Q

Most drugs are eliminated this way:

A

first order drug elimination

6
Q

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

A

first order

7
Q

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

A

kE

8
Q

What are the units for kE?

A

units of reciprocal time

9
Q

How do you calculate kE given starting plasma concentration?

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

A

starting plasma concentration * (1-kE)

480 ng/ml

10
Q

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

What are the units?

A

half-life

time

11
Q

t1/2 is _________ proportional to kE.

A

inversely

12
Q

Estimate the half life of the drug:

A

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

13
Q

Calculate half life from Log Plasma Concentration versus time plot

t1/2 =

A

-0.301/1

14
Q

What determines duration of action of a single dose?

A

half-life

15
Q

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

A

5-6

16
Q

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

A

chronic

17
Q

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

A

margin of safety

18
Q

Half life is an _____ process.

A

exponential

19
Q

Drug administration is ____ order and elimination is ____ order.

A

zero

first

Because taking the pill does not depend on plasma concentrations.

20
Q

What type of curve is this?

A

Plot of drug absorption and elimination

Elimination rate exceeds absorption so curve peaks

21
Q

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

A

blood flow
slow-release preparations

22
Q

Slower absorption means (2)

A

Lower peak concentrations
Longer duration of action

23
Q

______ plasma concentration is reached under:

• first order drug elimination
A

24
Q

Most drugs given _____ every half life.

A

once

25
Q

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

A

plasma clearance

ml/min

26
Q

CLp = Σ _____organs

A

CL of all

27
Q

CLp equation:

A

rate of elimination
plasma concentration

28
Q

KNOW

What equation is this?

CSS * CLp

Concentration of steady state * clearance in plasma

A

29
Q

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?

A

true

6.5 mg/hr

30
Q

Clearance (CL) is __________ to half life.

A

inversely proportional

31
Q

CL is dependent on Vd. True or false?

A

false

independent

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

32
Q

It takes__-___ half-lives to reach steady- state.

A

5-6

33
Q

KNOW

Time to reach new CSS depends only on the ___

A

half life

exponential

34
Q

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

A

cumulative poisoning

35
Q

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

A

mean concentration

36
Q

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

A

Drug half-life
Size of therapeutic window
Convenience and patient compliance

37
Q

A

drugs with a long T

rapid onset needed for emergency

38
Q

A
• plasma concentration
• volume of distribution
• bioavailability

[(concentration) (Vd)] / F

Note: F is bioavailability

39
Q

A

2

like z pack

40
Q

A

smaller

41
Q

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

A

refine estimate of clearance

refine estimate of bioavailability

42
Q

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

A
• Allow long enough after dosing for distribution phase to be over
• Usually, best time is right before a scheduled dose
43
Q

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

A

true

in order to get an accurate estimate of steady state

44
Q

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

A
• Therapeutic window may vary with individuals
• Knowledge of previous plasma concentrations is important
45
Q

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

A

zero order kinetics of drug elimination

46
Q

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

A

zero order kinetics

47
Q

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

A

false

48
Q

For oral or other routes, rate of administration equation is:

What are the units?

A

Css * CLp
F

mg/min

Note: F is bioavailability, CLp is plasma clearance