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Flashcards in Pharmacokinetics Deck (54):
1

After 5 half lives _______% of the drug is gone.

After 5 half lives 97% of the drug is gone.

_________________

Unlikey to have any more effect

2

Most drugs in veterinary medicine follow _________ kinetics

Most drugs in veterinary medicine follow First Order kinetics

3

Half-life (T1/2) equation

t1/2 = 0.693 x Vd / ClB

4

When saturation occurs, ClB (increases/decreases) and t1/2 (increases/decreases) leading to drug accumulation and potential development of side effects.

When saturation occurs, ClB (increases/decreases) and t1/2 (increases/decreases) leading to drug accumulation and potential development of side effects.

5

T/F: Half life is dose dependent

False, it is proportional

6

Dosage

"Recipe" for how much to give (mg/kg)

7

Bioavailability % (F%) equation

F% = AUC (extravascular) / AUC (IV) x 100%

8

F% is equal to ________ for IV administration

F% is equal to 100 for IV administration

9

One Compartment Model

Consider the body as consisting of a single, homogeneous compartment. Volume would equal the volume of distribution.  Model may be closed or open taking in account for clearance.

10

Primary compartment method by which pharmacokinetic parameters are now determined in veterinary medicine

Stochastic model 

(Non-Compartmental)

11

Zero Order Kinetics

Amount of drug is eliminated per unit time is fixed

12

Peak

Highest concentration of each dose

13

Dose

The amount of a drug given to an individual (mg)

 

14

Time to achieve steady state levels is (dependent/independent) of dose.

Independent

15

What are the components of a dosage regimen

Dosage

Route of Administration

Frequency

Duration

16

Plasma Concentration Steady State is reached at how many half lives

5

17

Extent

How much the mass (dose) of a drug changes in total

18

Loading Dose

Single dose administered to get the plasma concentration to a certain level, to be maintained by repeated dosing

19

Compartment Model

Views the patient as a number of compartments, each compartment is a collection of tissues that have similar pharmacokinetics

20

Pharmacokinetics

Use of mathematical modelsto quantitate the time course of drug disposition in man and animals

21

Allometric Scaling

Uses pharmacokinetic data in multiple species to try to predict the behavior of a drug in a species for which this information is unknown

22

What type of pharmacokinetic model is used for drugs that follow first order kinetics?

Non-Linear Model

23

Clearance

Volume cleared of the drug per unit time (mL/min/kg)

24

What happens to plasma concentration and half life if a dose is doubled?

Plasma concentration will increase

Half life will remain the same

25

Population Pharmacokinetics

System estimates pharmacokinetics by looking at populations.  Mathematical techniques allow studies of large numbers of animals with less individual sampling.  Can allow for development of parameters for a drug that would apply to all breeds/ages/genders/etc.

26

Elimination roughly equals

Metabolism + Excretion

27

As Vd increases, t1/2 (increases/decreases)

Increases

28

Multi-Compartment Model

Consists of multiple compartments.  Math gets incredibly complex

29

Vd Equation

Vd = Dose / Cp

30

Bioavailability (F)

Fraction of the dose given which finds its way into systemic circulation

31

Intermittent Dosing Cpss Equation

       DOSE x F       = Cpss x CLB

                               Interval

32

Two Compartment Model

Considers the body as consisting of two compartments; a central compartment into which the drug is added and from which it is clear and a second compartment to which the drug distributes.  Graphical representation shows a distribution and elimination phase.

33

DoseCRI Equation

= Cpss x CLB

34

As Clearance increases, t1/2 (increases/decreases)

Decreases

35

Trough

Lowest concentration of each dose

36

Describe the pattern of Plasma Concentration of a drug in relation to Plasma Elimination of a drug

Plasma concentration will follow the same pattern as plasma elimination, only upside down

________________________

1 half life - 50% of final Cpss

5 half lives - Cpss will be 97% of eventual steady state

37

Apparent Volume of Distribution (Vd)

Theoretical volume a drug would occupy if it was evenly distriuted through the body at the same concentration as in plasma

38

First Order Kinetics

Proportion of drug eliminated per unit time is fixed

39

Elimination Rate Constant

Fraction/ Proportion of the drug that would be eliminated per unit time

40

Volume of Distribution (Vd)

Volume of drug would occupy if it was evenly distributed at the same concentration as in plasma (L/kg)

41

Very high Vd ( > L/kg ) suggests that a drug is 

Very high Vd ( > L/kg ) suggests that a drug is distributing preferentially to tissue and may even be sequestered somewhere

42

Total Body Clearance (CLB)

Volume of distribution of drug in body cleared of teh drug per unit time (mL/min/kg) and this is the sum of clearance by the kidneys, liver and everywhere else.

____________________

Takes into account both metabolism and excretion

43

Bioavailability (F) equation

F = AUC ( extravascular ) / AUC (IV)

44

Very low Vd suggests that a drug is

Very low Vd suggests that a drug is not being distributed to all of the tissues

45

After 2 half lives _______% of the drug is gone.

After 2 half lives 75% of the drug is gone.

46

Bioequivalence

Different formulations of the same drug have the same drug bioequivalence when they are absorbed to a similar extent and similar rate

47

Stochastic Model

(Non-Compartmental)

Involve using analysis of large numbers of actual animal data (time-plasma curves).

48

Elimination Half Life

Time required for the drug concentration to decrease by one half or 50%

49

Rate

How fast the mass (dose) of a drug changes per unit time (mg/min)

50

Bioavilability is a measure of 

Bioavilability is a measure of  drug exposure

51

What measurements are important to compare in bioequivalence

AUC

Cmax

Tmax

52

Mean Resistance Time (MRT)

Used in the non compartment model, describes the length of drug persistence in the body

53

Plasma Concentration at Steady State Cpss

Concentration at which the amount of drug going in is equal to the amount going out

54

After 3.3 half lives _______% of the drug is gone.

After 3.3 half lives ~90% of the drug is gone.