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Flashcards in Pharmacokinetics Deck (49):
1

Why doesn't eating a poisoned animal kill you?

Poison is highly ionised drug so cannot be absorbed into the bloodstream

2

Define pharmacology.

Origin, nature, chemistry, effects and uses of drugs

3

Define toxicology.

Study of the adverse effects of chemical, physical or biological agents

4

Define pharmacodynamics.

What the drug does to the body

5

Define pharmacokinetics.

What the body does to the drug

6

List the 4(/5) stages of pharmacokinetics.

ADME:
(Liberation)
Absorption
Distribution
Metabolism
Excretion

7

List the 7 different types of drug administration.

Oral
Sublingual (under the tongue)
Inhalation
Topical
Transdermal (directly onto the skin)
Intramuscular
Intravenous

8

Give the advantages and disadvantages of oral drug administration.

ADVS:
Convenient
DISADVS:
First pass effect
Many variables & barriers

9

Give the advantages and disadvantages of sublingual drug administration.

ADVS:
No first pass effect
DISADVS:
Inconvenient
Small dose limit
Taste

10

Give the advantages and disadvantages of inhalation drug administration.

ADVS:
Fast, rapid delivery to blood
DISADVS:
Requires special drug properties (e.g. atomised, vaporised)

11

Give the advantages and disadvantages of topical drug administration.

ADVS:
Convenient
Localised
DISADVS:
Only local

12

Give the advantages and disadvantages of transdermal drug administration.

ADVS:
Prolonged release
DISADVS:
Skin is a very effective barrier

13

Give the advantages and disadvantages of intramuscular drug administration.

ADVS:
Rapid for aqueous, slow for oil
DISADVS:
Painful
Requires trained personnel

14

Give the advantages and disadvantages of intravenous drug administration.

ADVS:
Direct
Total dose
Rapid
DISADVS:
Requires professional
Infection risk
Rapid response

15

What is the meaning of bioavailability?

The fraction of unchanged drug that reaches the systemic circulation

16

Which method of drug administration gives 100% bioavailability?

Intravenous (IV)

17

There are four ways in which small molecules cross cell membranes - name them.

Diffusion directly through phospholipid bilayer
Diffusion through aqueous pores
Transmembrane carrier proteins
Pinocytosis (vesicles)

18

Describe the solubility of hydrophilic drugs.

Soluble in aqueous, polar media

19

Describe the solubility of lipophilic drugs.

Soluble in fats & non polar solutions

20

What can you say about the lipid solubility of ionised drugs?

Low lipid solubility

21

Which range of pH do many drugs fit into?

Weak acids or weak bases

22

What are the main drug properties affecting absorption?

Lipophilicity
Ionisation

23

Name some factors that affect drug distribution.

Degree of ionisation
Lipid solubility
pH of compartments
Cardiac output & blood flow
Capillary permeability
Plasma protein binding

24

What does the compartment model state?

Some drugs occupy a single, well stirred compartment with a set volume, but some can occupy a peripheral compartment in addition

25

Why is having a high affinity for calcium an advantageous feature of the phosphonate group in bisphosphonates?

The drug can be quickly distributed to the skeleton

26

What factor can cause large increases in free drug concentrations

Competition for binding sites

27

Is it the bound drug or unbound drug concentration that has the pharmacological effect on the body?

Unbound

28

Warfarin binds to albumin. As a percentage, how much of the drug is bound and how much is free to act?

98/99%
1/2%

29

In the presence however of aspirin, more like 2-4% of warfarin is left to act on the body. Why is this?

Aspirin has a high affinity for albumin

30

List the body fluid compartments and the relative percentages of drugs present in each.

Trans-cellular water: 2%
Plasma water: 5%
Interstitial water: 16%
Fat: 20%
Intracellular water: 35%

31

Where does drug metabolism generally occur?

The liver

32

What are the two phases of drug metabolism?

Phase 1: oxidation, reduction or hydrolysis creating reactive products used in phase 2...
Phase 2: synthetic, conjugative reactions generating hydrophilic, inactive compounds

33

What do monooxygenases do?

They are enzymes that add (a) hydroxyl group(s) to a compound/molecule.

34

Give an example of a group of enzymes that are members of the monooxygenase family.

Cytochrome P450 Enzymes

35

How do these monooxygenase enzymes act on paracetamol?

Cytochrome P450 enzymes metabolise a small proportion of the paracetamol drug into a toxic metabolite

36

What is the effect on warfarin if the concentration of enzyme metabolising it (CYP450) is increased?

The effectiveness of the warfarin drug decreases due to the fact that the drug is being metabolised

37

What is the drug simvastatin metabolised by and where does this occur?

CYP3A4
The gut wall and the liver

38

What increases the expression of CYP450s?

Phenobarbital

39

What is meant by the first pass effect?

The concentration of a drug is greatly reduced before it reaches the systemic circulation

40

What does grapefruit juice do?

Blocks CYP3A4

41

List onset, duration and metabolism/elimination for Vecuronium.

Medium
Medium
Liver - eliminated via urine & bile

42

List onset, duration and metabolism/elimination for Atracurium.

Medium
Medium
Spontaneous degradation in plasma

43

List onset, duration and metabolism/elimination for Mivacurium.

Fast
Short
Plasma cholinesterase

44

What is the 'aim' of drug metabolism?

To produce metabolites that can be excreted

45

Barring elimination from the lungs, which type of drugs are eliminated more readily: hydrophilic drugs or lipophilic drugs?

Hydrophilic drugs

46

List some possible sources of excretion of drug metabolites.

Breath
Urine
Saliva
Perspiration
Faeces
Milk
Bile
Hair

47

What happens to plasma drug concentration during IV infusion?

Increases until rate of input equals rate of output - reaches a 'steady state'

48

What is meant by 'T max'?

The amount of time that a drug is present at maximum concentration in the plasma/in serum

49

What is meant by 'C max'?

The maximum plasma concentration of the drug