Brainscape's Knowledge GenomeTM

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


See full index

Principles of dizzees > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

Absorption Distribution Excretion

1
Q

What is drug pharmacokinetics?

A

How drugs move around the body

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

What 4 factors determine drug pharmacokinetics?

ADME

A

Absorption

Distribution

Metabolism

Elimination

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

In pharmacokinetics, what does absorption refer to?

A

Process of movement of an unchanged drug from the site of administration to the systematic circulation

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

What is Tmax?

A

Time until drug concentration in circulation is at its peak, from when it was administrated

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

What is the Cmax?

A

Peak concentration of the drug in circulation

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

The area under the concentration time graph of a drug in circulation gives what information?

A

The amount of drug that has been absorbed and not excreted

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

What effect does dosage have on Cmax and Tmax?

A

No effect on rate of absorption so no affect on Tmax

Dosage determines Cmax

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

What is the therapeutic range?

A

Range of concentrations of the drug that will be effective over

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

What is bioavailability?

A

Amount of drug that reaches circulation

compared to how much was administered

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

Which method of administration of a drug has the highest bioavailability?

A

Intravenous

100% bioavailability

Bioavailability of other methods compared to IV

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

What factors affect bioavailability of a drug?

A

Formulation

Ability to pass physiological barriers

Gastrointestinal effects

First pass metabolism

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

What is first pass metabolism?

A

Drug metabolism, prior to reaching systematic circulation

Liver, gut lumen, gut wall

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

What might affect a patients gastrointestinal ability to absorb a drug?

A

Gut motility

Food they’ve eaten

Illness

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

Why is it important that oral drugs must be in an un-ionised state in the stomach?

A

So they can pass through the plasma membrane of cells lining the stomach

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

What is the effect of ion trapping?

A

Drugs trapped in cells they are trying to diffuse through

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

“An acidic drug will be more concentrated in the compartment with a ____ pH due to ion trapping”

A

High (alkaline)

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

What is the lipid-water partition coefficient?

A

Ability for a drug to diffuse across a lipid barrier

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

If a drug is easily metabolised by the body, what methods of administration are suitable to use?

A

IV

Subcutaneous /Intra-muscular

Sublingual/buccal (under tongue)

Rectal

Transdermal

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

What effect does plasma protein binding have on drug distribution?

A

When a drug is bound to in the blood plasma, it can not be diffuse out ∴ can not be distributed to other sites in the body

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

What are the main proteins that bind to drugs in the plasma?

A

Albumin

alpha1-glycoprotein

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

What factors affect the amount of drug that is bound to by proteins? (5)

A

Renal failure

Hypoalbuminaemia

Pregnancy

Saturability of binding

Other drugs

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

Describe the drug distribution of a 95% protein bound drug, and how this would be affected by a 5% decrease in the amount of protein binding.

A

Drug distribution is quite low, only 5% isn’t bound to ∴ 95% remains in blood

5% decrease means a 100% increase in the amount of drug that is biologically available and leaves the circulation

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

What is the apparent volume of distribution?

A

The volume of plasma that would be necessary to account for the total amount of drug in a patient’s body, at the same concentration as found in the plasma

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

If a patient is given 1000mg of a drug, and the plasma drug concentration found in a plasma sample is 50mg/L, what is the apparent volume of distribution?

A

1000/50 = 20L

20L

(should be expressed as L/kg)

25
Q

What does a high apparent volume of distribution value mean?

A

High Vd ∴ higher the ability for the drug to diffuse out and through membranes

26
Q

What apparent volume of distribution value would a lipid soluble drug have and why?

A

High

Lipid soluble ∴ diffuses easily across membranes

27
Q

What is the ‘clearance’ of a drug?

A

Theoretical volume from which a drug is removed over a period of time

It is a measure of the rate of elimination

ml/min

28
Q

The clearance rate is basically a combination of two clearing ‘systems’, what are they, and what affects each?

A

Renal - urine concentration and flow rate

Hepatic - billiary secretion and metabolism rate

29
Q

What is the half life of a drug?

A

Time taken for concentration in the blood to drop to 50% of it’s original value

30
Q

What is half life proportional and inversely proportional to?

A

Proportional to A. Volume of distribution

Inversely proportional to clearance rate

31
Q

As a rule of thumb, how many half lives does it take for a drug to (pretty much) be removed from the system?

A

5 half lives

32
Q

Pathologies can often prolong the half life of a drug. What are the problems with this?

A

Reduction in clearance / large VOD

∴ abnormally high amount of drug remains in the body ∴ toxicity

33
Q

Define the elimination of a drug .

A

Removal of the active drug, and it’s metabollites from the body

Governed by the metabolism and excretion of the drug

34
Q

Where does metabolism usually take place?

A

Liver

35
Q

What organ is mainly responsible for excretion of a drug?

not bladder

A

Kidneys

Biliary system/gut, lung and milk are also involved with excretion

36
Q

What are the 3 mechanisms that affect excretion rate, at the kidneys?

A

Glomerular filtration - most important

Passive tubular reabsorption

Active tubular excretion

37
Q

Which excretion system is responsible for eliminating protein bound cationic and anionic drugs?

A

Active tubular secretion

38
Q

What happens with passive tubular re-absorption?

A

Drugs move from renal tubule back into circulation

Down concentration gradient (passively)

Only un-ionised drugs can do this

39
Q

Sum up the stages entero-hepatic circulation, of a drug.

A

Intestine to blood

Blood to liver

Liver to bile

Bile to intestine

(will repeat unless the drug is conjugated)

40
Q

Describe what conjugation of a drug is.

A

Metabolism in liver leads to conjugation

When secreted into bile, then into intestine, the drug is not absorbed again

41
Q

If the liver is damaged, and conjugation does not take place effectively, how could this cause toxicity?

A

No conjugation ∴ drug re-absorbed more

Hepatic elimination rate decreases

Drug build up

Toxicity

42
Q

True or false

Most excretion takes place in the kidneys

A

True

43
Q

Define drug metabolism

A

The biochemical modification of pharmaceutical substances by living organisms

44
Q

What type of organic molecule is key in drug metabolism?

A

Enzymes

45
Q

Why must lipid-soluble substances be converted to water-soluble substances by the body?

A

So they can be excreted

Lipid soluble substances would be constantly re-uptook and pass back into blood circulation

46
Q

What is the purpose of metabolism of drugs?

A

Make them more water-soluble, so they can be excreted

Deactivate the compounds (except from prodrugs which are activated by metabolism)

47
Q

What potential problem is associated with metabolism of drugs?

A

Production of toxic metabolites

  • Direct toxicity
  • Teratogenesis
  • Carcinogenesis
48
Q

What is teratogenesis?

A

the process by which congenital malformations are produced in an embryo or fetus

49
Q

What is carcinogenesis?

A

the initiation of cancer formation

50
Q

What are the 2 phases of drug metabolism?

A

Inactivation / activation (if prodrug)

Conjugation

51
Q

What type of reactions can take place in phase 1 metabolism of drugs?

A

Oxidation
Reduction
Hydrolysis

52
Q

What group of enzymes are important in phase 1 metabolism?

A

Cytochrome P-450 enzymes

These are often called CYP1A2, for example

53
Q

What is the effect of Phase 1 metabolism?

A

Increases polarity of compound and provides an active site for phase 2 metabolism

54
Q

In phase 2 metabolism, there is conjugation of the drug.

What are the effects of this?

A

Increase water solubility (for excretion)

Usually involves in-activation of the drug (a small number of active metabolites may remain however)

55
Q

Chemical groups that are made in phase 1 metabolism, can be added onto the metabollite in phase 2.

Give examples of some of these groups.

A

Glucuronic acid, glutathione, suplhate, acetate

56
Q

List some factors that effect metabolism of drugs.

A 
Other drugs/herbals/natural substances 
Genetics
Hepatic blood flow
Liver disease
Age 
Sex 
Ethnicity
Pregnancy
57
Q

What effect can other substances, such as herbal medicines, have on enzymes involved with drug metabolism?

A

Induction (increased metabolism of drug = less drug effect)

Inhibition (drug isn’t metabolised effectively = build up of active drug, often toxicity)

58
Q

What age category of people are most effective at metabolising drugs?

A

Adolescents

Principles of dizzees (28 decks)

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