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Pharmacology -- Test #1 > Final Pharmacokinetics > Flashcards

Final Pharmacokinetics Flashcards

(59 cards)

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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

Study These Flashcards
A

The amount of drug elimintated/time

25
Equation for half life
=0.693 * (Vd/CL) or 0.693 / Ke
26
One more time -- the constant number you'll probably forget on the test that's in that stupid halflife equation.
0.693
27
In first order rxns, what do increases in drug concentration do to half life.
Nothing.
28
How does a decrease in CL influence halflife?
Makes it longer
29
How does a bigger Vd influence halflife?
Makes it longer
30
Why use a semi-log plot?
makes conc/time linear to provide a slope that correlates with Ke?
31
True or False. Clearance concepts are not applicable once the concentration pushed into saturation.
True
32
______% of the final plateau reached after 4.5 half lives | ____% of the total dose eliminated after 4.5 half lives
95
33
Three reasons to give a shit about half life
Used to determine time to steady state w/ chronic dosing Used to determine duration of action Used to determine dosing frequency
34
95% of the Css will be reached after _____ half lives.
4.5
35
Doubling a dose will increase the duration of action by....
One half life
36
Why does it matter if you check half life when managing dosing frequency
Its required to avoid too large fluctuations in plasma conc during the dosing interval
37
Benefit of increased frequency of doses
Less fluctuations in Cp | The extreme -- IV injection -- No fluctuation
38
AUC of 1st dose =
AUC of 1 interval at Css
39
The semilog CT curve can be described with what equation
Cpt = Co * (e)^-kt
40
What does it mean if a drug cannot be described by the straight line on the semi-log CT curve?
It must be a multi compartmental model
41
What # compartment model
2-compartment model is the most common
42
First order Vd=
Dose/Cp
43
Why might it be important to know the -Ke in a Vd with elimination graph?
Elimination Rate Constant (the slope) can be used to extrapolate a value for Co when a measured concentration can't be found.
44
When in the one-compartment model on the linear graph, | Cp at a given time is equal to...
Co*e^(-Ke*t)
45
Assumptions used for the one compartment model
Must be first order Body one homogenous compartment Instantaneous mixing
46
Distribution between compartments is _____ than distribution within a compartment
slower
47
Distribution phase is typically about how long?
1-2 hours
48
Once a concentration has distributed...the concentration is _____
even
49
Material in this course assumes that compartment and concentrations are in .....
post distribution phase
50
Equation used for two compartment model (see page 17 of the notes if the typed version looks like a fucking mess)
Cp = A*e^(ke*t) + B*e(ke*t)
51
Maintenance dose rate for IV:
DR = CL*Css
52
Maintenance dose rate for PO:
=CL*(Css/F)
53
Loading dose for IV:
=Vd*target Cp
54
Loading dose for PO:
=(Vd*target Cp) / F
55
Dosing interval = T1/2 | Cmax/Ctrough ratio =
2
56
Dosing interval
57
Dosing interval > T1/2 | Cmax/Ctrough ratio =
>2
58
Equation to adjust a dosage regimen
New Rate = Old Rate * (Desired Css/Measured Css)
59
What kinds of drugs are especially important to monitor
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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