Pharmokinetics

Question 1

Which part of the GIT are oral drugs primarily absorbed?

Answer 1

Small intestine

Question 2

What is a potential problem with drugs that have slow distribution?

Answer 2

They are eliminated

Question 3

What is a potential complication with low bioavailable drugs?

Answer 3

They are more sensitive to variability

Question 4

Why is the peak drug concentration for oral administration lower than IV?

Answer 4

Drug is eliminated while being absorbed

Not all drug is absorbed

Some drug undergoes first past metabolism

Question 4

How do you prevent drug accumulation with zero order drugs?

Answer 4

Give small doses

Question 6

What is renal clearance dependent on?

Answer 6

Drugs filtration and secretion (out of the blood) and reabsorption (but into blood)

Question 7

What is a loading dose for?

Answer 7

Get a drug to it’s steady state quickly

Question 7

What do the elderly lack in liver metabolism?

Answer 7

Cytochrome P450

Question 9

What is renal clearance?

Answer 9

The amount of blood from which drug is removed by the kidneys over time

Question 9

What happens to the half life of some drugs in the neonates and the elderly?

Answer 9

Increased

Question 10

When is complex drug behaviour most relevant?

Answer 10

When the therapeutic window is small

Question 11

What is phase I metabolism?

Answer 11

Creation of a functional group on the metabolite

Question 11

What is the relationship between C at steady state and infusion rate?

Answer 11

Directly proportional

Question 11

How long does it take for a drug to get to 99% of its steady state concentration?

Answer 11

7 half-lives

Question 11

What long does it take for babies drug metabolism to mature?

Answer 11

6 weeks

Question 12

What is the bioavailable for IV drugs?

Answer 12

100%

Question 12

In theory, when is steady state reached with a zero order elimination drug?

Answer 12

Never

Question 14

What enzyme subfamily does a lot of phase I metabolism?

Answer 14

Cytochrome P450

Question 15

Where are acidic drugs most lipid soluble?

Answer 15

In areas of low pH

Question 15

What is phase II metabolism?

Answer 15

Conjugation of a water soluble molecule to a functional group on drug

Question 15

What is local metabolism?

Answer 15

Metabolism prior to absorption eg in the gut or intramuscularly

Question 16

How long does it take for newborn’s renal clearance to increase to adult levels (size proportionate)

Answer 16

1 week

Question 17

When is renal function at its peak?

Answer 17

20 year olds

Question 19

What is the pattern of drug administration over time when it’s added IV?

Answer 19

Exponential excretion

Question 21

Compare the peak concentrations when drug is added IV bolus or infusion?

Answer 21

Bolus reaches a higher peak concentration for a given amount of drug

Question 22

What is the renal clearance of newborns?

Answer 22

20% of adult (size proportional)

Question 23

What must you do with drugs with small therapeutic windows?

Answer 23

Plasma monitoring

Question 24

What is the maximal GFR?

Answer 24

120ml/min

Question 25

How much relative renal clearance do 75 y.o. have?

Answer 25

50%

Question 27

What will the variation in drug concentration be when drug is given every half-life?

Answer 27

2 fold variation

Question 28

Is the peak concentration higher with a fast or slowly distributing drug?

Answer 28

Slow

Question 29

What can you do in response to an overdose?

Answer 29

Add a compound that will change the pH to the opposite of what is optimal of absorption of the overdosing drug. Eg add NaHCO3 to make urine more basic when overdosed on acidic aspirin

Question 30

What is bioavailability?

Answer 30

The amount of active drug that enters the systemic circulation

Question 32

What happens to drug clearance as concentration in the blood increases?

Answer 32

It increases

Question 33

What does making a drug more water soluble do to its secretion?

Answer 33

Decrease its lipid solublity \> less absorption into cells \> more secreted

Question 34

Where is the first place drugs go when they are absorbed in the gut?

Answer 34

The Liver

Question 35

How do drugs behave if they are added IV?

Answer 35

Rapidly distribution Act as if in one compartment

Question 36

What are the 4 possible outcomes of metabolism?

Answer 36

Inactivation of a drug Activation of a drug Activation of a different drug Toxic metabolite

Question 38

When is IV infusion better than IV bolus?

Answer 38

When the therapeutic window is small

Question 40

What is the rate of drug absorption in the gut?

Answer 40

First order: dependent on the concentration

Question 41

How do most drugs get across the gut wall?

Answer 41

Diffusion through lipid membranes

Question 42

What are the typical peripheral compartment for a drug?

Answer 42

Muscle and fat

Question 43

What can be done address low bioavailability with oral administration?

Answer 43

Administer via a different route that avoid first pass metabolism