Brainscape's Knowledge GenomeTM

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


See full index

ESA1 - Physiology and Pharmacology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

What is pharmacokinetics?

A

The effect of the body on drugs

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

What are the four main processes in pharmacokinetics?

A

Absorption, distribution, metabolism and elimination

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

What are some examples of enteral drug administration?

A

(Delivery into GI tract)

Oral, sublingual, rectal

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

What are some examples of parenteral drug administration?

A

Intravenous, intramuscular, subcutaneous

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

What is the length and diameter of the small intestine?

A

6-7m length, 2.5cm diameter

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

What is the total surface area for absorption in the small intestine?

A

30-35m^2

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

What does the constant GI movement do to the drug?

A

Mixing - presents drug molecules to GI eptihelia

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

What is the typical transit time through the small intestine?

A

3-5 hours

Varying motility = 1-10 hours

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

What is a common mechanism for the absorption of lipophilic drugs?

A

Passive diffusion - diffuse directly down concentration gradient into GI capillaries

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

What is PKa?

A

The pH at which 50% of the species is ionised

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

What drugs can be absorbed via passive diffusion?

A

Lipophilic

Weak acids/bases (eg valproate - anti-epileptic)

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

Where are SLCs highly expressed?

A

GI, hepatic and renal epithelia

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

How can molecules or solutes with net ionic charge within GI pH range can be carried across GI epithelia by what?

A

Solute Carriers

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

How is fluoxetine absorbed?

A

Co-transported with Na+ ion

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

How is B lactam antibiotics/penicillin absorbed?

A

Co-transported with H+ ion

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

What factors can affect drug absorption?

A

GI length/SA
Drug lipophilicity/pKa
Density of SLC expression in GI
First pass metabolism

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

What is first pass metabolism?

A

A phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation

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

How does first pass metabolism affect drug absorption?

A

In gut lumen: enzymes can denature some drugs

In gut wall/liver: cytochrome P450s and conjugating

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

What are phase I and II enzymes?

A

Phase I - cytochrome P450s

Phase II - conjugating enzymes

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

What is bioavailability?

A

Proportion of a drug which enters the circulation when introduced into the body and so is able to have an active effect.

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

If a drug is given intravenously, what is the bioavailability?

A

100% as there are no physical barriers to overcome

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

What is the equation for oral bioavailability (F)?

A

F = amount reaching systemic circulation/total drug given IV

23
Q

What are the factors affecting drug distribution?

A
  • Drug lipophilicity (if lipophilic, can move across membranes)
  • Capillary permeability
  • Drug pKa and local pH
  • Presence of OATs/OCTs
  • Degree of drug binding to plasma/tissue proteins
24
Q

What kinds of proteins could drugs bind to in circulation?

A

Eg albumin, globulins, lipoproteins, acid glycoproteins

25
Q

What does binding of drugs to plasma/tissue proteins do?

A

Decreases free drug available for binding, acts as ‘reservoir’

Binding can be up to 100% (aspirin is around 50%)

26
Q

What is the total body fluid in an average human?

A

42 litres

27
Q

How much fluid is extracellular in an average human?

A

14 litres

28
Q

How much fluid is plasma in an avergae human?

A

3 litres

29
Q

What is apparent volume of distribution? (Vd)

A

The theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma.

30
Q

What do smaller Vd values mean?

A

Less penetration of interstitial/intracellular fluid compartment

31
Q

What do larger Vd values mean?

A

Greater penetration of interstitial/intracelullar fluid compartment

32
Q

What is the equation for volume of distribution?

A

Vd = drug dose/concentration of plasma drug

33
Q

Where does drug metabolism mostly take place?

A

Liver via phase I and II enzymes

34
Q

What ionic charge do metabolised drugs have?

A

Increased ionic charge

35
Q

What are drugs activated by phase I metabolism called?

A

Prodrugs

36
Q

What is an example of a prodrug?

A

Codeine to morphine (higher affinity for opioid receptor)

37
Q

How do phase II enzymes enhance hydrophilicity?

A

Further increase ionic charge - add to phase I

38
Q

How do phase II enzymes catalyse?

A

Sulphation, glucorinadation, glutathione conjugation, methylation, N-acetylation

39
Q

How do phase I enzymes catalyse?

A

Redox, dealkylation, hydroxylation

40
Q

What does phase I and II metabolism do?

A

Increase ionic charge to enable rapid elimination from the body. Metabolism usually renders pharmacologically inactive.

41
Q

What factors affect drug metabolism?

A

Age, sex, general health, other drugs, genetic polymorphism

42
Q

What is Carbamezepine (CBZ) and what does it induce?

A

Anti-epileptic metabolised by CYP3A4 - induces CYP3A4 - lowering its own levels affecting control of epilepsy

43
Q

What is an example of CYP450 inhibition?

A

Grapefruit juice

44
Q

Where is the main route of drug elimination?

A

Kidney (but other routes include bile, lung, breat milk, sweat, tears)

45
Q

What are the three processes in renal excretion?

A
  • Glomerular filtration
  • Active tubular secretion
  • Passive tubular secretion
46
Q

What is clearance?

A

Rate of elimination of a drug from the body

47
Q

What is total body clearance?

A

Total body clearance = hepatic clearance + renal clearance

48
Q

What is clearance measured in?

A

ml/min

49
Q

What is drug half life?

A

The amount of time over which the concentration a drug in plasma decreases to one half of that concentration value it had when it was first measured

50
Q

What is half life dependent on?

A

Vd and CL

51
Q

What happens to half life if CL stays the same and Vd increases?

A

Half life increases

52
Q

What happens to half life if CL increases and Vd stays the same?

A

Half life decreases

53
Q

What is the clinical importance of zero order kinetics?

A

Drugs at or near therapeutic dose with saturation kinetics - more likely to result in ADRs/toxicity.

ESA1 - Physiology and Pharmacology (11 decks)

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