Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Yr 2 Sem 2 CPT > 2.1 Pharamacokinetics > Flashcards

2.1 Pharamacokinetics Flashcards

You may prefer our related Brainscape-certified flashcards:
NASM ® CPT flashcards
1
Q

Define Pharmacokinetics

A

Study of the movement of a drug into and out of the body

What the body does to the drug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define pharmacodynamics

A

Study of drug effect and mechanisms of action

What the drug does to the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define pharmacogenetics

A

The effect of genetic variability on the pharmacokinetics or dynamics of a drug on an individual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does bioavailability translate or clinical practice?

A

Calculate correct formulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does estimating half life translate into clinical practice?

A

Allows dosing regimes to be devised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What processes occur as part of pharmacokinetics?

A

Absorption
Distribution
Metabolism
Elimination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the therapeutic window?

A

Range of plasma concentration in which the drug has the desired effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define bioavailability (F)

A

The FRACTION of a dose which finds its way into a body compartment, usually the circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the bioavailability for an IV bolus?

A

100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the axis for a bioavailability curve?

A

X time post dose

Y plasma concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does the area under a bioavailability curve represent?

A

Total drug exposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How can oral bioavailability be calculated?

A

F = AUC oral / AUC IV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What factors affect bioavailability?

A

Absorption
- drug formulation, age, food, vomiting, malabsorption

First pass metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What sort of drug formulation is preferable and why?

A

Modified release once a day

Short half life needs to be given many times a day. Immediate release may dip out of the therapeutic window

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is first pass metabolism?

A

Any metabolism occurring before the drug enters the systemic circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Name three areas where first pass metabolism can occur

A

Gut lumen
Gut wall
Liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe the effect of first pass metabolism in the gut lumen

A

Affect3 by gastric acid, proteolytic enzymes, grapefruit juice

Affects benzylpenicillin, insulin, cyclosporin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe the action of first pass metabolism in the gut wall

A

P-glycoprotein efflux pumps drugs out of the intestinal enterocytes back into the lumen
Eg ciclosporin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Name a drug that is extensively metabolised in the liver

A

Propranolol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are two key factors in drug distribution?

A

Protein binding

Volume of distribution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Which state should drugs be in to have a therapeutic effect normally?

A

Unbound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What causes protein binding drug interactions?

A

Displacement of drugs from binding sites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What factors affect protein binding?

A

Hypoalbuminaemia
Pregnancy
Renal failure
Displacement by other drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

In what circumstances will changes in protein binding causing changes in drug distribution be important?

A

High protein binding
Low Vd
Narrow therapeutic window

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe what happens when you add a highly bound precipitant drug (B) to drug A

A

More highly protein bound drug b will steal binding sites
Increase free drug a
(Increases effects of a)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is volume of distribution a measure of?

A

How widely a drug is distributed in body tissues

27
Q

How can Vd be calculated?

A

Dose/ concentration of drug at time 0

28
Q

What is half life proportional to?

A

Vd and clearance

29
Q

What can Tissue distribution be affected by?

A 
Specific receptor sites in tissues 
Regional blood flow 
Lipid solubility
Active transport
Disease states 
Drug interactions
30
Q

Where does the majority of drug metabolism occur?

A

Liver

31
Q

What should the end products of conjugation be soluble in after metabolism?

A

Water to allow rapid elimination from the body

32
Q

What are the two ways active metabolites can be formed in metabolism?

A

Metabolism of an inactive compound to active one (pro-drug)

Metabolism of an active compound to another active compound

33
Q

Give an example of a pro drug

A

L dopa

34
Q

Give an example of an active drug that is metabolised by liver to another active drug

A

Codeine to morphine

35
Q

What factors can influence the activity of p450 enzymes?

A 
Enzyme inducing/inhibiting drugs 
Age
Liver disease 
Hepatic blood flow
Cigarette and alcohol consumption
36
Q

Where can CYP450s be found?

A

Mainly liver

Some gut and lung

37
Q

Give an example of drug interaction due to enzyme inhibition

A

Cimetidine inhibits CYP causing there to be higher concentrations of warfarin in the plasma
Higher risk of bleeding

38
Q

Describe the genetic distribution of CYP 2D6

A

Absent in 7% of Caucasians

Hyperactive in 30% of east Africans

39
Q

What drugs are metabolised by CYP 2D6?

A

Codeine
Beta blockers
Tricyclics

40
Q

What drugs are inhibited by CYP 2D6?

A

Fluoxetine
Paroxetine
Haloperidol
Quinidine

41
Q

What is the main route of drug elimination?

A

Kidney

42
Q

What are some other routes of drug elimination? (Other than kidney)

A

Lungs, breast milk, sweat, tears, genital secretions, bile, saliva

43
Q

What three processes determine the renal excretion of Drugs?

A

Glomerular filtration
Passive tubular reabsorption
Active tubular secretion

44
Q

What drugs are excreted through glomerular filtration?

A

Unbound drugs like gentamicin

45
Q

What drugs are actively secreted in nephron excretion?

A

Penicillin

46
Q

Which drugs are removed by passive reabsorption and what are they affected by?

A

Aspirin

Affected by urine flow rate and pH

47
Q

What is clearance and what is it dependent on?

A

Ability of body to excrete a drug

Dependent on GFR (renal function)

48
Q

What is the relationship between half life and clearance?

A

Half life is inversely proportional to clearance

49
Q

What effect will a reduced GFR have on clearance and half life p?

A

Reduced clearance

Increased half life

50
Q

Describe the rate of elimination in first order kinetics (linear)

A

Rate if elimination proportional to drug level
Constant fraction of drug eliminated in unit time
Half life can be defined

51
Q

Describe the rate of elimination in zero order kinetics (non linear)

A

Rate of elimination is constant

52
Q

In which type of kinetics can half life be defined?

A

First order/linear

53
Q

What is the equation for half life?

A

Half life = 0.693 x Vd/CL

54
Q

What type of kinetics do most drugs exhibit at high dose and why?

A

Zero order

Because the receptors/enzymes become saturated

55
Q

Why are zero order drugs more likely to produce toxicity?

A

Fixed rate of elimination per unit time

Small dose changes may produce large increments in plasma concentration

56
Q

What qualities of a drug may mean they require more monitoring?

A 
Zero order kinetics
Long half life
Narrow therapeutic window
Greater risk of interactions with other drugs 
Known toxic effects
57
Q

In how many half lives will steady state of a drug be achieved?

A

3-5
(Irrespective of dose of frequency of administration)

Drugs with larger half lives take longer to reach steady state

58
Q

How many half lives will it take to eliminate a drug from steady state?

A

4 to 5

59
Q

What can affect the maintenance dose of a drug?

A

Age and renal function

60
Q

True or false : loading dose can remain much the same in renal failure

A

True

61
Q

True or false: maintenance dose can remain much the same in renal failure

A

False

Should be reduced

62
Q

How can loading dose be calculated?

A

Loading dose = VD x target drug concentration

63
Q

How can you work out elimination rate constant (k)?

A

K = clearance / Vd

64
Q

How can drug elimination be improved in someone with renal failure?

A

Give a drug that will bind the drug in the plasma to inactivate it

Yr 2 Sem 2 CPT (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions