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PHAR226 > PK Overview > Flashcards

PK Overview Flashcards

1
Q

What is the goal of an empirical dosage regimen?

A

attain and maintain therapeutic plasma drug concentrations (Cp, ther) to treat a condition effectively

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2
Q

What does Cp,ther mean?

A

the drug plasma concentration that results in therapeutic effect
-drug effect depends on Cp
-Cp determined by DR and PK

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3
Q

What does Css,ave stand for?

A

average steady state plasma concentration

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4
Q

What is the therapeutic window?

A

range of Cp which produces desired clinical response in a patient
-between MTC and MEC
-drug has clinically beneficial effects when Cp are within TW

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5
Q

What does the clinical response refer to?

A

onset, intensity, and duration

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6
Q

True or false: most drugs have narrow TWs

A

false
most drugs have wide TWs

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7
Q

Differentiate between onset, duration, and intensity.

A

onset: when Cp reaches TW
duration: length of time Cp stays within TW
intensity: height of Cp within TW or toxic range

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8
Q

Which PK descriptive parameters are related to onset, duration, and intensity?

A

onset: Tmax
duration: t1/2
intensity: Cmax

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9
Q

True or false: plasma drug concentration relates to drug concentration at site of action and in turn the clinical response

A

true

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10
Q

What is the relationship between plasma concentration and tissue concentration?

A

as plasma concentration increases so does tissue concentration

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11
Q

What are the common exposure metrics used in PK?

A

AUC (area under the Cp vs time curve)
Cp,ss (average steady state plasma concentration)
Cmax (maximum plasma concentration)

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12
Q

What is the goal of dosing for therapeutic purposes?

A

produce drug exposures that result in clinically relevant drug response

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13
Q

What is pharmacokinetics?

A

study of the time course of drug concentrations in the blood and relationship between concentration and time course of drug action such as onset, intensity, and duration of action
study of drug ADME and mathematical relationships describing Cp vs time profiles

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14
Q

What are the key pharmacokinetic parameters?

A

F, Ka, Cmax, Tmax
-how much or how quickly drug is absorbed (absorption)
Vd, Fu(b)
-how body distributes drug into tissues and organs (distribution)
Cls, fe
-how body eliminates (metabolizes or excretes) drug (metabolism)
t1/2, k
-how body distributes and eliminates drug
AUC
-total body exposure to the drug over time
Css
-average steady state concentrations in the plasma

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15
Q

What are the primary PK parameters?

A

Ka, F, Vd, Cls
determined only by the physiological system

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16
Q

What are the secondary PK parameters?

A

t1/2, k, fe
determined by the primary PK parameters

17
Q

What are the derived PK parameters?

A

AUC, Css, Css,ave, Tmax, Cmax
determined by the primary PK parameters of from Cp vs t curve

18
Q

Differentiate between linear and non-linear PK.

A

linear PK
-predictable relationship between dose and Cp
-proportional increase of AUC or Cp,ss with increased dose
non-linear PK
-no predictable relationship between dose and Cp
-disproportional increase of Cp,ss with increased dose

19
Q

What is responsible for interindividual variation in clinical response following a dose administration?

A

PK and PD

20
Q

How do we categorize the processes of ADME?

A

absorption
disposition processes (processes observed once drug is circulating)
-distribution
-metabolism
-excretion

21
Q

Provide the definition for the processes of ADME.

A

absorption:
-passage of intact drug from site of admin into systemic circulation
-Ka, F
distribution:
-reversible movement of drug between systemic circulation and tissue
-Vd, fu(b)
metabolism:
-irreversible enzymatic alteration of the drug
-Cls
excretion:
-irreversible passage of drug/metabolite out of body (renal, billiary)
-Cls

22
Q

Differentiate between the extravascular and intravascular routes of administration.

A

extravascular
-administration outside the systemic circulation
-requires absorption into systemic circulation
intravascular
-administration directly into systemic circulation

23
Q

We dont know an individuals therapeutic window, therefore what do we use to know if the dosing regimen is appropriate for the patient?

A

clinical response or therapeutic range

24
Q

What is the therapeutic range?

A

establishes probability of success in typical population

25
Q

What is the therapeutic index?

A

ratio of toxic Cp to effective Cp
-wide TI=safe drug
-narrow TI=toxicity at “usual” doses possible

26
Q

What is a loading dose?

A

dose to attain therapeutic concentrations quickly

27
Q

How is loading dose determined?

A

must know Cther and Vd
LD=Cther x Vd/S x F

28
Q

What is a maintenance dose?

A

dose to maintain therapeutic concentrations
-achieves Css,ther

29
Q

How is maintenance dose determined?

A

MD=Css x Cls/S x F

30
Q

How is steady state concentration determined?

A

Css=MD/Cls

31
Q

What is Cls?

A

sum of all pathways contributing to the elimination of the drug

32
Q

What is F?

A

bioavailability
- % dose reaching systemic circulation intact

33
Q

When is Css,ther reached?

A

5-7 half lives

34
Q

What is t1/2?

A

time taken for Cp to decrease by one half

35
Q

Why is t1/2 important?

A

determines time to Css
determines dosing interval

36
Q

What is k?

A

elimination rate constant
-fraction of drug eliminated per unit time

37
Q

How is t1/2 determined?

A

0.693 x Vd/Cls

38
Q

How is k determined?

A

k=Cls/Vd

39
Q

What is the use of AUC?

A

measure of total body exposure
-depends upon how much drug gets into the body and how quickly the body can eliminate the drug

PHAR226 (12 decks)

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