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Hugh's MD1 Abdominal > Pharmokinetics > Flashcards

Flashcards in Pharmokinetics Deck (43):
1

Which part of the GIT are oral drugs primarily absorbed?

Small intestine

2

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

They are eliminated

3

What is a potential complication with low bioavailable drugs?

They are more sensitive to variability

4

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

Drug is eliminated while being absorbed

Not all drug is absorbed

Some drug undergoes first past metabolism

4

How do you prevent drug accumulation with zero order drugs?

Give small doses

6

What is renal clearance dependent on?

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

7

What is a loading dose for?

Get a drug to it's steady state quickly

7

What do the elderly lack in liver metabolism?

Cytochrome P450

9

What is renal clearance?

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

9

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

Increased

10

When is complex drug behaviour most relevant?

When the therapeutic window is small

11

What is phase I metabolism?

Creation of a functional group on the metabolite

11

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

Directly proportional

11

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

7 half-lives

11

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

6 weeks

 

12

What is the bioavailable for IV drugs?

100%

12

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

Never

14

What enzyme subfamily does a lot of phase I metabolism?

Cytochrome P450

15

Where are acidic drugs most lipid soluble?

In areas of low pH

15

What is phase II metabolism?

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

15

What is local metabolism?

Metabolism prior to absorption eg in the gut or intramuscularly

16

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

1 week

17

When is renal function at its peak?

20 year olds

19

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

Exponential excretion

21

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

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

22

What is the renal clearance of newborns?

20% of adult (size proportional)

23

What must you do with drugs with small therapeutic windows?

Plasma monitoring

24

What is the maximal GFR?

120ml/min

25

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

50%

27

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

2 fold variation

28

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

Slow

29

What can you do in response to an overdose?

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

30

What is bioavailability?

The amount of active drug that enters the systemic circulation

32

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

It increases

33

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

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

34

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

The Liver

35

How do drugs behave if they are added IV?

Rapidly distribution

Act as if in one compartment

36

What are the 4 possible outcomes of metabolism?

Inactivation of a drug

Activation of a drug

Activation of a different drug

Toxic metabolite

38

When is IV infusion better than IV bolus?

When the therapeutic window is small

 

40

What is the rate of drug absorption in the gut?

First order: dependent on the concentration

41

How do most drugs get across the gut wall?

Diffusion through lipid membranes

42

What are the typical peripheral compartment for a drug? 

Muscle and fat

43

What can be done address low bioavailability with oral administration?

Administer via a different route that avoid first pass metabolism