Quantitative pharmacokenitics part 2

Question 1

What type of graph is obtained after administering a sing IV dose?

Answer 1

An expoenetial decay graph

Question 2

When is only time tou know the amaount of drug injected into a patient?

Answer 2

Straight after injecting it

Question 3

The larger the volume of drug distributed the shorter the half life. TRUE OR FALSE?

Answer 3

TRUE

Question 4

What is the equation for exponential decay?

Answer 4

C=C0e-Kt

Question 5

If we know volume distribution we can calculate the dose for any given concentration. TRUE OR FALSE?

Answer 5

TRUE

Question 6

What equation can be used to calculate the dose for any given concentration?

Answer 6

Vd=Dose/C0

Question 7

Doubling the dose does not extend exposure above a certain concentration by t1/2? TRUE OR FALSE?

Answer 7

FALSE

Question 8

What does K represent?

Answer 8

The fraction of volume distribution that is cleared per min.

Question 9

What is the equation for rate of elimination?

Answer 9

K=Cl/Vd

Question 10

Larger volume distribution results in slower elimination . TRUE OR FALSE?

Answer 10

TRUE

Question 11

WHAT ARE THE TWO FACTORS THAT DETERMINE HOW QUICK A DRUG IS ELIMINATED?

Answer 11

Clearance and volume distribution

Question 12

What factors control half life?

Answer 12

-Controlled by how much volume of the drug appears to be dissolved in and by what volume of plasma is cleared per unit time.

Question 13

What are the factors affecting elimination, in terms of Vd and Clearance?

Answer 13

Effects on volume distribution:

• Aging
• Obesity
• Pathologic fluid

Effects on clearnace:

• Cytochrome P450 induction/Inhibition
• Cardiac failure
• Hepatic failure
• Renal failure

Question 14

What effects do these factors have elimination?

Answer 14

• Aging - decreased distribution
• Obesity - increased distribution
• Pathologic fluid -increased distribution
• Cytochrome P450 induction - increased metabolism
• Cytochrome P450 Inhibition - decreased metabolism
• Cardiac failure - decreased clearance
• Hepatic failure - decreased clearance
• Renal failure - decreased clearance

Question 15

What is intravenous infusion?

Answer 15

Drug being delivered constanly (i.e via a pump)

Question 16

What is a loading dose?

Answer 16

Allows us to very rapidly occupy the entire volume of distribution with the drug

Question 17

What are the pros for Iv infusion?

Answer 17

• Allows precise and controlled exposure
• Adjust concentration
• Stop if required
• Short infusion sometimes used to reduce maximum concentration and adverse events following rapid bolus injection

Question 18

What is the constant steady state?

Answer 18

Drug concentartion increases to a plateau value

Question 19

At Css, rate of elimination is equals to rate of infusion. TRUE OR FALSE?

Answer 19

TRUE

Question 20

What is the equation for rate of infusion?

Answer 20

Rinf= Cl *Css

Question 21

What is the equation for loading dose?

Answer 21

Css * Vd

Question 22

How many half lifes does it aproximately take to reach plateau?

Answer 22

3.3 t 1/2

Question 23

What is plateau concentration determined by?

Answer 23

Infusion rate and clearance

Question 24

Increasing infusion rate will increase final Css. TRUE OR FALSE?

Answer 24

TRUE

Question 25

The time taken to reach the plateau depends on half life or rate of elimination. TRUE OR FALSE?

Answer 25

TRUE

Question 26

What is occured in zero order elimination?

Answer 26

Drug is eliminated at a constant rate and independent of drug concentration

Question 27

What ocurs in linear pharmacokinetics?

Answer 27

The pharmacokinetics parameters do not change with dose,increasing dose increases exposure

Question 28

What is non linear pharmacokinetics?

Answer 28

The pharmacokinetic parameters chnage with dose of drug, increasing dose has no effect on exposure

Question 29

Drugs can be absorbed by either zero order or first order processes. TRUE OR FALSE?

Answer 29

TRUE

Question 30

What is the equation for the rate of increase of drug in the body?

Answer 30

Rate of absorption - Rate of elimination

Question 31

Absorption and elimination are comepeting pathways. TRUE OR FALSE?

Answer 31

TRUE

Question 32

It takes longer for drugs that are administered orally to available in the systemic circulation. TRUE OR FALSE?

Answer 32

TRUE

Question 33

What occurs dose is increased?

Answer 33

- Increased Cmax and AUC | - There is no effect on Tmax

Question 34

What occurs to Cmax and Tmax when a drug is given via P.O with food?

Answer 34

Cmax and Tmax are altered

Question 35

Absorption can become rate limiting when it occurs extremely slowly. TRUE OR FALSE?

Answer 35

TRUE

Question 36

What controls the rate of absorption?

Answer 36

rate of elimination

Question 37

What equation can be used to determine the rate of elimination in P.o administration?

Answer 37

Kel=Cl/Vd

Question 38

What symbol is used to represent bioavailability?

Answer 38

F

Question 39

What factors can affect bioavailability?

Answer 39

- incomplete absorption - poor dissolution - poor permeability - metabolism before absorption

Question 40

If the bioavailability of the drug is low, a larger dose can be given, TRUE OR FALSE?

Answer 40

TRUE

Question 41

What equation can be used to determine the amount of drug reachin systemic circulation?

Answer 41

ARSC= F*Dose

Question 42

How can we measure bioavailability?

Answer 42

By measuring th AUC

Question 43

What is required for Css max in a repeated dose?

Answer 43

Needs to be less than the concentration at which toxicity is observed

Question 44

What is required for Css min in a repeated dose?

Answer 44

Needs to be greater than the concentration required to have a therapeutic effect

Question 45

How can bioavailbility be determined when when doses are equal?

Answer 45

Bioavailability is the ratio of the two AUC

Question 46

What is the average constant steady state dependent upon?

Answer 46

Dose and frequency

Question 47

Why is a loading dose important for drugs that have larger Vd?

Answer 47

Takes longer to reach constant steady state, as drug is being distributed to other parts of the body.

Question 48

What is a maintenance dose?

Answer 48

once desired plasma drug concentration is achieved, then a maintenance dose compensates for drug elimination