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Pharmacology -- Test #1 > Final Pharmacokinetics > Flashcards

Final Pharmacokinetics Flashcards

1
Q

Dose Rate =

A

<p>(CL)*(SS Conc)</p>

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2
Q

Equation for renal clearance

A

CL = Filtration + Secretion - Reabsorption

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3
Q

Markers for GFR

A

Creatinine and Inulin

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4
Q

Renal Dosage Adjustment Equation

A

= Average Dose * (Creatinine Clearance/100(normal))

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5
Q

When should you worry about adjusting for renal clearance

A

When kidneys do at leas half the clearing and fxn is at least half down

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6
Q

Characteristics of first order elimination

A

Elimination of a drug that is within its therapeutic range of concentration. In this condition, elimination is proportional to a percentage. Cp is linearly accumulated with dose.

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7
Q

Maintenence Dose Equation

A

DR = CL * Css

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8
Q

What makes zero-order elimination different than first order?

A

At their therapeutic concentration, the drug elimination capacity is saturated. This is caused by complete usage of the enzymes/transporters

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9
Q

Relationship of drug elimination and drug concentration in zero order rxn? first order rxn?

A

0 – Linear

1 – Exponential

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10
Q

The accumulation of drug concentration in zero-order rxns is….

A

Non-linear

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11
Q

Three go-to zero order drugs

A
  1. Ethanol
  2. Phenytoin
  3. Aspirin
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12
Q

In first order elimination, drug elimination occurs at a ______ rate

A

Exponential (Same percentage cut every time)

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13
Q

In zero order elimination, elimination occurs at a _____ rate

A

Linear (Same AMOUNT of drug lost each time)

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14
Q

In first order dosing, Plasma concentration is ____ accumulated with dose

A

Linearly

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15
Q

In zero order dosing, plasma concentration is

A

non-linear

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16
Q

Michaelis-Menton Equation

A

Elimination Rate = (Max Velocity of rxn)(conc) / (Drug conc at 50% Vmax) + C

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17
Q

What does Vmax refer to?

A

The max velocity of a reaction at a very high drug concentration

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18
Q

What does Km refer to?

A

The drug concentration at 50% of Vmax

A measure of affinity of the substrate for the enzyme

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19
Q

According to Michaelis-Menten, If a system is not saturated, increasing concentration will _____ elimination. When the rate is at its max, elimination will _____ with increases in concentration.

A

Increase

do nothing. no increase in conc.

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20
Q

When asked for assumptions for the models in the last PK lecture, always write

A

Elimination must be first order

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21
Q

What is half life

A

The time is takes to eliminate 50% of a drug from the body

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22
Q

What is the Elimination Rate constant?

A

Fraction of the drug eliminated/time

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23
Q

Equation for elimination rate constant

A

Clearance/Vd

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24
Q

What is elimination rate

A

The amount of drug elimintated/time

25
Q

Equation for half life

A

=0.693 * (Vd/CL)
or
0.693 / Ke

26
Q

One more time – the constant number you’ll probably forget on the test that’s in that stupid halflife equation.

A

0.693

27
Q

In first order rxns, what do increases in drug concentration do to half life.

A

Nothing.

28
Q

How does a decrease in CL influence halflife?

A

Makes it longer

29
Q

How does a bigger Vd influence halflife?

A

Makes it longer

30
Q

Why use a semi-log plot?

A

makes conc/time linear to provide a slope that correlates with Ke?

31
Q

True or False. Clearance concepts are not applicable once the concentration pushed into saturation.

A

True

32
Q

______% of the final plateau reached after 4.5 half lives

____% of the total dose eliminated after 4.5 half lives

A

95

33
Q

Three reasons to give a shit about half life

A

Used to determine time to steady state w/ chronic dosing
Used to determine duration of action
Used to determine dosing frequency

34
Q

95% of the Css will be reached after _____ half lives.

A

4.5

35
Q

Doubling a dose will increase the duration of action by….

A

One half life

36
Q

Why does it matter if you check half life when managing dosing frequency

A

Its required to avoid too large fluctuations in plasma conc during the dosing interval

37
Q

Benefit of increased frequency of doses

A

Less fluctuations in Cp

The extreme – IV injection – No fluctuation

38
Q

AUC of 1st dose =

A

AUC of 1 interval at Css

39
Q

The semilog CT curve can be described with what equation

A

Cpt = Co * (e)^-kt

40
Q

What does it mean if a drug cannot be described by the straight line on the semi-log CT curve?

A

It must be a multi compartmental model

41
Q

What # compartment model

A

2-compartment model is the most common

42
Q

First order Vd=

A

Dose/Cp

43
Q

Why might it be important to know the -Ke in a Vd with elimination graph?

A

Elimination Rate Constant (the slope) can be used to extrapolate a value for Co when a measured concentration can’t be found.

44
Q

When in the one-compartment model on the linear graph,

Cp at a given time is equal to…

A

Coe^(-Ket)

45
Q

Assumptions used for the one compartment model

A

Must be first order
Body one homogenous compartment
Instantaneous mixing

46
Q

Distribution between compartments is _____ than distribution within a compartment

A

slower

47
Q

Distribution phase is typically about how long?

A

1-2 hours

48
Q

Once a concentration has distributed…the concentration is _____

A

even

49
Q

Material in this course assumes that compartment and concentrations are in …..

A

post distribution phase

50
Q

Equation used for two compartment model (see page 17 of the notes if the typed version looks like a fucking mess)

A

Cp = Ae^(ket) + Be(ket)

51
Q

Maintenance dose rate for IV:

A

DR = CL*Css

52
Q

Maintenance dose rate for PO:

A

=CL*(Css/F)

53
Q

Loading dose for IV:

A

=Vd*target Cp

54
Q

Loading dose for PO:

A

=(Vd*target Cp) / F

55
Q

Dosing interval = T1/2

Cmax/Ctrough ratio =

A

2

56
Q

Dosing interval

A
57
Q

Dosing interval > T1/2

Cmax/Ctrough ratio =

A

> 2

58
Q

Equation to adjust a dosage regimen

A

New Rate = Old Rate * (Desired Css/Measured Css)

59
Q

What kinds of drugs are especially important to monitor

A

Marked PK variability
Narrow Safety Margins
Therapeutic/Adverse effects related to drug conc.
Difficulty monitoring for desired therapeutic effect

Pharmacology -- Test #1 (8 decks)

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