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MD2002 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Why doesn’t eating a poisoned animal kill you?

A

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

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2
Q

Define pharmacology.

A

Origin, nature, chemistry, effects and uses of drugs

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3
Q

Define toxicology.

A

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

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4
Q

Define pharmacodynamics.

A

What the drug does to the body

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5
Q

Define pharmacokinetics.

A

What the body does to the drug

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6
Q

List the 4(/5) stages of pharmacokinetics.

A 
ADME:
(Liberation)
Absorption
Distribution
Metabolism
Excretion
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7
Q

List the 7 different types of drug administration.

A 
Oral
Sublingual (under the tongue)
Inhalation
Topical
Transdermal (directly onto the skin)
Intramuscular
Intravenous
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8
Q

Give the advantages and disadvantages of oral drug administration.

A 
ADVS:
Convenient
DISADVS:
First pass effect
Many variables & barriers
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9
Q

Give the advantages and disadvantages of sublingual drug administration.

A 
ADVS:
No first pass effect
DISADVS: 
Inconvenient
Small dose limit
Taste
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10
Q

Give the advantages and disadvantages of inhalation drug administration.

A

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

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11
Q

Give the advantages and disadvantages of topical drug administration.

A 
ADVS:
Convenient
Localised
DISADVS:
Only local
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12
Q

Give the advantages and disadvantages of transdermal drug administration.

A

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

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13
Q

Give the advantages and disadvantages of intramuscular drug administration.

A 
ADVS:
Rapid for aqueous, slow for oil
DISADVS:
Painful
Requires trained personnel
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14
Q

Give the advantages and disadvantages of intravenous drug administration.

A 
ADVS:
Direct
Total dose
Rapid
DISADVS:
Requires professional
Infection risk
Rapid response
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15
Q

What is the meaning of bioavailability?

A

The fraction of unchanged drug that reaches the systemic circulation

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16
Q

Which method of drug administration gives 100% bioavailability?

A

Intravenous (IV)

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17
Q

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

A

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

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18
Q

Describe the solubility of hydrophilic drugs.

A

Soluble in aqueous, polar media

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19
Q

Describe the solubility of lipophilic drugs.

A

Soluble in fats & non polar solutions

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20
Q

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

A

Low lipid solubility

21
Q

Which range of pH do many drugs fit into?

A

Weak acids or weak bases

22
Q

What are the main drug properties affecting absorption?

A

Lipophilicity

Ionisation

23
Q

Name some factors that affect drug distribution.

A 
Degree of ionisation
Lipid solubility
pH of compartments
Cardiac output & blood flow
Capillary permeability
Plasma protein binding
24
Q

What does the compartment model state?

A

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

25
Q

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

A

The drug can be quickly distributed to the skeleton

26
Q

What factor can cause large increases in free drug concentrations

A

Competition for binding sites

27
Q

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

A

Unbound

28
Q

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

A

98/99%

1/2%

29
Q

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

A

Aspirin has a high affinity for albumin

30
Q

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

A 
Trans-cellular water: 2%
Plasma water: 5%
Interstitial water: 16%
Fat: 20%
Intracellular water: 35%
31
Q

Where does drug metabolism generally occur?

A

The liver

32
Q

What are the two phases of drug metabolism?

A

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

33
Q

What do monooxygenases do?

A

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

34
Q

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

A

Cytochrome P450 Enzymes

35
Q

How do these monooxygenase enzymes act on paracetamol?

A

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

36
Q

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

A

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

37
Q

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

A

CYP3A4

The gut wall and the liver

38
Q

What increases the expression of CYP450s?

A

Phenobarbital

39
Q

What is meant by the first pass effect?

A

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

40
Q

What does grapefruit juice do?

A

Blocks CYP3A4

41
Q

List onset, duration and metabolism/elimination for Vecuronium.

A

Medium
Medium
Liver - eliminated via urine & bile

42
Q

List onset, duration and metabolism/elimination for Atracurium.

A

Medium
Medium
Spontaneous degradation in plasma

43
Q

List onset, duration and metabolism/elimination for Mivacurium.

A

Fast
Short
Plasma cholinesterase

44
Q

What is the ‘aim’ of drug metabolism?

A

To produce metabolites that can be excreted

45
Q

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

A

Hydrophilic drugs

46
Q

List some possible sources of excretion of drug metabolites.

A 
Breath
Urine
Saliva
Perspiration
Faeces
Milk
Bile
Hair
47
Q

What happens to plasma drug concentration during IV infusion?

A

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

48
Q

What is meant by ‘T max’?

A

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

49
Q

What is meant by ‘C max’?

A

The maximum plasma concentration of the drug

MD2002 (27 decks)

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