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Pharmacology Exam 1 (Lauren) > L5 Pharmacokinetics II > Flashcards

L5 Pharmacokinetics II Flashcards

1
Q

What does a large Vd mean?

A

The drug get distributed to peripheral tissues beyond the plasma

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2
Q

What does a small Vd mean?

A

It means that the drug stays mostly in the blood

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3
Q

As plasma levels of a drug fall, what happens to the drug that went into the storage depots (fat, tissues, bone, transcellular)?

A

They come out of their storage depots, down their concentration gradients and into the plasma.

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4
Q

What kind of drugs accumulate in the fat?

A

Highly lipid soluble drugs like anesthetics

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5
Q

What kinds of drugs accumulate in bone?

A

Cheating drugs like tetracyclines

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6
Q

If a drug has a high plasma protein binding, what does its Vd probably look like?

A

It probably has a low Vd, meaning it accumulates in plasma

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7
Q

What does plasma protein binding do to a drug’s half life?

A

Prolongs it

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8
Q

How do you calculate Vd?

A

Vd= Total dose of drug given/plasma concentration

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9
Q

Is the fetus acidic or basic compared to the mother?

A

Acidic. Basic drugs will get trapped

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10
Q

IS Breast milk more acidic or basic than plasma?

A

More acidic

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11
Q

What kind of drugs get trapped in breaks milk?

A

Basic and lipid-soluble

Tetracyclines, phenobarbital

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12
Q

What are sites of drug exclusion

A

Sites where drugs would have to be injected in order to get to those spaces.
Ex: CSF, ocular fluid, fetal fluid, pleural fluid

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13
Q

How are most drugs eliminated

A

1st order

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14
Q

What is first-order elimination?

A

Percentage of the drug eliminated/time

Depends on plasma concentration

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15
Q

Why would we plot the elimination of a first-order drug in a semi-logarithmic form?

A

Gives us a straight line that makes it easy to calculate half life

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16
Q

What is half life?

A

Time required to decrease the plasma concentration by 50%

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17
Q

What the half life of a drug with Vd=40L and CL of 5 L/hr?

A

T 1/2= (0.7 Vd)/CL
= (.7x40)/5
=5.6 hours

18
Q

What is the half life of a drug in an 80kg man if the Vd= 0.57L/Kg and CL=5?

A

T 1/2= (0.7 x 0.57x80)/5

= 6.4 hr

19
Q

How long do you need to wait to determine Css plasma levels?

A

About 5 half lives

20
Q

Is the time to reach CSS related to the size of the dose you gave them?

A

NO it is only related to half life

Remember
Half life= (0.7 x Vd)/CL

21
Q

Shortening the dosing internal or increasing the dose will have what effect on Css?

A

Increase

22
Q

What is zero-order elimination?

A

Constant AMOUNT eliminated over unit of time

23
Q

Does half life apply to zero-order elimination?

A

NO

24
Q

What is the elimination of ethanol?

What kind of elimination is it (1st or 0 order)

A

10g/hr

Zero order elimination

25
Q

If you plot the elimination of a zero-order drug on a logarithmic scale, what kind of line do you get? Curved or straight

A

curved

26
Q

If you give a zero order drug repeatedly in high doses, will you develop steady state levels?

A

No, because its not dependent on plasma levels

27
Q

What happens when you give zero order drugs at higher doses than their elimination rate?

A

They will accumulate in the body and produce excessive plasma levels and toxicity

28
Q

What is Clearance? CL

A

The volume of plasma from which a drug is removed per unit of time

29
Q

How do you calculate CL?

A

CL= Vd x (0.7/half life)

Just flipping around the equation for T 1/2

30
Q

What is the CL of a drug with a Vd=100L and T 1/2=2 hours

A

CL= (.7 x Vd)/ half life

CL=35 L/hr

31
Q

What is the CL if Vd=100: and half life is 2 hours in a 80kg patient?

A

First you calculate Vd in L/kg

Vd=100L/70kg = 1.43 L/kg

CL= (.7 x 1.43 x 80)/2

CL=40 L/hr

32
Q

What is the standard weight that Vd’s apply to?

A

70kg patient

33
Q

How do you calculate CL?

A

CL= (Vd)(.7/ t 1/2)

34
Q

What 3 things are directly proportional to the Css?

A

Dose, bioavailability, and T 1/2

35
Q

What 2 things are in the denominator of the Css equation

A

CL and Vd

36
Q

How many 1/2 lives does it take to reach CSS

A

5

37
Q

How do you calculate dosing rate/elimination rate?

A

(CL)(TC)
_________
F

38
Q

How do you calculate the maintenance dose?

A

(Dosing rate)(dosing interval)

Remember dosing interval is

CL x TC
__________
F

39
Q

What is F in the dosing rate calculation if drug is infused?

A

1

Dosing rate: CL x TC / F

40
Q

How fo you calculate loading dose

A

LD= Vd x TC

41
Q

Why would you administer a loading dose

A

To achieve immediate therapeutic plasma concentrations

Pharmacology Exam 1 (Lauren) (7 decks)

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