PharmacoKINETICS

Question 1

Define PharmacoKINTETICS…

Answer 1

What the animal does to the drug

Question 2

Rate=

Answer 2

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

Question 3

Extent=

Answer 3

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

Question 4

PharmacoKINETICS allows us to evaluate the rate and extend of…..

Answer 4

Absorption
Distribution
Elimination

Question 5

Non-compartmental (stochastic) models

Answer 5

Most common in vet med.
statistical moments – like the Mean Residence Time (which basically represents the average amount of time any given molecule of drug stays in the body).

Question 6

________: This system estimates pharmacokinetics by looking at populations

Answer 6

Population pharmacokinetics

Question 7

_______: This uses pharmacokinetic data in multiple species to try to predict the behavior of a drug in a species for which this information is unknown.

Answer 7

Allometric scaling / Interspecies Extrapolation

Question 8

Non-linear models

Answer 8

Used when drugs follow zero-order kinetics

Question 9

the fraction of the given dose which finds its way into systemic circulation. This is calculated from the area under the plasma concentration-time curve (AUC)

Answer 9

Bioavailability (F)

Question 10

Comparing 2 formulations of the same RX. Trade name VS generic

Answer 10

Bioequivalence

Question 11

CMAX (maximum plasma concentration) and TMAX (the time at which CMAX is reached

Answer 11

Bioequivalence

Question 12

Half-life (t1/2):

Answer 12

time required for the drug concentration to decrease by one-half (or 50%).

Question 13

amount of drug eliminated per unit time is fixed, regardless of plasma concentration. There are relatively few drugs used in veterinary medicine that normally follow this.

Answer 13

Zero-order elimination/kinetics

Question 14

The proportion of drug eliminated per unit time is fixed. The vast majority (maybe 95%) of drugs used in veterinary medicine will follow this type of kinetics at therapeutic doses, and for these drugs the compartment or stochastic models work well for predicting pharmacokinetics

Answer 14

First-order elimination/kinetics

Question 15

Drugs that normally undergo first-order elimination may convert to zero-order if a _______ dose is given and elimination systems are saturated.

Answer 15

Massive/over

Question 16

When saturation occurs the clearance (CLB) decreases and the half-life (t1/2) increases which can lead to…

Answer 16

RX accumulations AND potential toxicity

Question 17

After 1 half-life ___% of the drug is gone

Answer 17

50%

Question 18

After 2 half-lives ___% of the drug is gone

Answer 18

75%

Question 19

After 3.3 half-lives ~___% of the drug will be gone

Answer 19

~90%

Question 20

After 5 half-lives ~___% of the drug will be gone

Answer 20

~97%

Question 21

What if we administered 2x normal dose to a food animal. Would we decrease holding time? Increase holding time? No change, and release animal at normal dose holding time?

Answer 21

We would INCREASE holding time by 1-HALF LIFE

Question 22

V/D stands for…

Answer 22

Volume of Distribution

Question 23

_____: the volume of a RX that would occupy if it was evenly distributed at the same concentration as in plasma (L/kg)

Answer 23

V/D

Question 24

CL B stands for…

Answer 24

Clearance from body

Question 25

_______: volume cleaned of the RX per unit time from the body

Answer 25

CL B

Question 26

Plasma Concentration at Steady State (CpSS)

Answer 26

is the concentration at which the amount of drug going in (repeated dosing or CRI) is equal to the amount going out (clearance CLB)

Question 27

If the dosing is continuous (CRI) plotting the plasma concentration over time would give a

Answer 27

Smooth curve

Question 28

intermittent dosing (SID, BID, TID) will give you a

Answer 28

Sawtooth pattern

Question 29

"peak" is...

Answer 29

Highest concentration of each dose

Question 30

"trough" is...

Answer 30

Lowest concentration of each dose

Question 31

as steady-state is reached the ‘peak’ value will not change day to day, nor will the ‘trough’ so if you wish to measure levels for therapeutic drug monitoring (TDM) you usually will..

Answer 31

choose a particular time of day and always measure it at that same time (eg. 4 hours after the morning dose)

Question 32

Is the theoretical volume a drug would occupy if it was evenly distributed through the body at the same concentration as in plasma

Answer 32

Apparent Volume of Distribution (Vd)

Question 33

Dose/Dosage

Answer 33

mass – e.g mg/kg

Question 34

Volume of Distribution

Answer 34

usually L/kg

Question 35

Plasma drug concentration

Answer 35

mg/L

Question 36

A very _______ Vd suggests that the drug is not being distributed to all of the tissues

Answer 36

LOW

Question 37

A very _____ Vd (>1L/kg) suggests that the drug is distributing preferentially to tissue and may even be sequestered somewhere

Answer 37

HIGH

Question 38

Total Body Clearance (CLB):

Answer 38

The volume of distribution of drug in the body cleared of the drug per unit time (mL/min/kg) and this is the sum of clearance by the kidneys, liver and everywhere else, thus CLB takes into account both metabolism and excretion

Question 39

As Vd increases t1/2 increases:

Answer 39

the wider a drug is distributed then it probably has more than one compartment and so that means it has to distribute back to the central compartment to be eliminated and that will take some time

Question 40

If the Vd is lower than that redistribution doesn’t happen and at the same clearance rate the drug will be gone sooner (shorter t1/2). T or F?

Answer 40

TRUE

Question 41

As Clearance increases t1/2 decreases:

Answer 41

if we are clearing the drug faster it will be hanging around the body for a shorter time.