Flashcards in PHARM: Clinical Pharmacokinetics Deck (40):

1

## True or False: IV administration is the fastest route of drug absorption.

### False- when administered via IV, there is no drug absorption

2

## How can the rate of elimination of a drug be calculated in a one-compartment model?

### Rate of Elimination (Vel)= Inherent rate of Elimination (Kel) * [Drug] in the body ([A]c)

3

## What does it mean if a drug follows a 1st order process of elimination?

### The drug elimination is proportional to the drug concentration in the body

4

## True or False: Kel is a constant for a particular drug.

### False: Kel can be different from individual to individual and can be different in the same individual at different times

5

## How can Kel be determined from a Semi-log plot of [drug] vs. time?

### Kel is the slope of the line

6

## What is the half life of a drug?

### The time it takes for half of the drug to be eliminated from the body

7

## What is the relationship between half-life and the elimination rate constant for first order drugs?

### Kel=0.693/T(1/2)

8

## What sorts of drugs are zero order drugs?

### Drugs whose metabolism or elimination is mediated by proteins, and thus, is saturable

9

## What is the appearance of a regular and semi-log plot of a zero order drug?

### Regular plots show a linear decrease, and semi-log plots are concave downward until the rxn is no longer is zero order

10

## How can the rate at which a drug is absorbed be calculated for a drug administered extravascularly in a one compartment model?

### Rate of absorption (Vabs)= absorptive rate constant for the drug (Kabs) * concentration of the drug at the absorptive site ([A]a)

11

## How can a drug following a one-compartment model and in a first order process be identified by looking at a semi-log plot?

### The semi-log plots for these drugs will simply be a straight line

12

## Following administration into a two compartment model via intravascular bolus and accumulation in the central compartment what two process can happen to the drug?

### Elimination or Distribution to peripheral compartment

13

## How can distribution from the central to peripheral compartment be calculated?

### Vcp= Kcp (rate constant for drug describing ability to distribute from central to peripheral compartments) * [A]c (conc. of drug in central compartment)

14

## How can distribution from the peripheral to central compartment be calculated?

### Vpc= Kpc * [A]p

15

## On a regular plot of a two compartment model drug what is alpha and what is beta? What is happening to the drug during those periods?

### Alpha is the distribution phase that consists of the rapid decrease in [drug] from initial concentration. Beta is the disposition phase, which consists of distribution, redistribution, and elimination of drug

16

## How can beta be calculated for a two-compartment model drug?

### Beta= 0.693/T(1/2)beta, where T(1/2)beta can be determined by using the linear portion of a semi log plot (indicating the cessation of distribution/redistribution)

17

## What are the three phases of a semi-log plot of a drug administered extravascularly into a 2 compartment system?

### Absorption, Distribution, Disposition

18

## What is the utility of apparent volumes of distribution?

### Gives an idea on where a drug goes once it enters the body

19

## How can apparent volumes of distribution be calculated?

### Give a patient a drug of a known amount, take blood levels (concentration) over time and then extrapolate the concentration to time point 0 prior to any elimination. Dividing the amount of drug by the concentration at time 0 will give the apparent volume of distribution

20

## A drug is given to a patient and has a calculated apparent volume of distribution equal to 5.5 L. Where is the drug primarily located?

### Within the vasculature

21

## A drug is given to a patient and has a calculated apparent volume of distribution equal to 14.6 L. Where is the drug primarily located?

### In the vasculature and ECF

22

## A drug is given to a patient and has a calculated apparent volume of distribution equal to 105.5 L. Where is the drug primarily located?

### Some tissue compartment of the body

23

## What is bioavailability?

### The fraction of drug that reaches systemic circulation- essentially a measure of absorption of a drug and how effectively it is absorbed

24

## How can bioavailability be determined?

### First administer a drug via IV, measure drug concentration over time and measure the area under the curve of a regular plot. Next administer the drug via extravascular route and obtain the area under the curve. Bioavailability (F)= AUCx/AUCiv

25

## What is the interpretation of "When administered sublingually, THC has an F of 1?"

### All of the THC that would have entered into systemic circulation directly via IV is the same amount that would get into circulation via sublingual administration

26

## What is clearance?

### The theoretical volume of fluid from which a drug is completely removed in a given period of time

27

## What two equations can be used to determine total clearance?

### Clt=Kel * Vd; =Xo/AUC

28

## What is the extraction ratio and how is it calculated?

### E is the efficiency at which an organ extracts a drug and is =(Cin - Cout)/(Cin)

29

## How could one determine clearance of a drug from the liver?

### Clh= Q (rate of blood flow) * E

30

## What are the three processes that contribute to renal clearance of a drug?

### Glomerular filtration, Active secretion, passive reabsorption

31

## How is renal clearance of a drug calculated?

### Clr=Clglomfilt + Cl (actsec) - Cl(tubReab)

32

## What is the minimum effective concentration?

### The concentration of a drug needed to produce its pharmacological effect

33

## What is the steady state concentration?

### The concentration at which a drug administered continuously has a dose rate = rate of elimination such that the blood concentration of a drug remains stable

34

## How can steady state concentration be calculated

### Css=dose rate/ Ct or dose rate/ Kel * Vd

35

## When administering a drug via IV infusion how long does it take for a drug to reach half of its steady state concentration?

### One half life

36

## When administering a drug via IV infusion how long does it take for a drug to reach its steady state concentration?

### 4-5 Half lives

37

## How does increasing the frequency of a smaller dose of a drug effect its pharmacokinetics?

### There is smaller fluctuations in the concentration level

38

## What is a loading dose? When is it needed? How can it be calculated?

### A loading dose is a higher first dose given when the therapeutic window must be reached quickly. Loading dose (X*)=Css *Vd

39

## How would a graph of multiple IV administrations differ from a graph of multiple extravascular administrations?

### The spikes on the fluctuations would be more rounded due to absorption slowing down the process

40