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Pharmacology Exam > Session 1 - Pharmacokinetics > Flashcards

Session 1 - Pharmacokinetics Flashcards

1
Q

Define pharmacology

A

The study of drugs

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2
Q

Define pharmacokinetics

A

The study of what the body does to the drug

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3
Q

Define pharmacodynamics

A

The study of what the drug does to the body

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4
Q

Define pharmacotherapeutics

A

The study of how to use the right drug at the right time

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5
Q

What are the 4 (ADME) principles of pharmacokinetics ?

A

Absorb
Metabolism
Distribution
Excretion

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6
Q

Where does oral tablets get metabolised ?

A

Within the liver

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7
Q

Define absorption

A

The movement of a drug into the blood circulation

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8
Q

Where will orally administered drugs be absorbed ?

A

Some of the drug will be absorbed through the stomach lining, however most absorption occurs in the small intestines.

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9
Q

After a drug has been absorbed by the small intestines, where does it go ? And what happens to it

A

Directly to the liver

Undergo first pass metabolism

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10
Q

Name 4 factors that effect absorption

A
  • Food
  • Other medicines - some medicines bind together and form a large compound which makes absorption difficult .
  • Controlled released drugs and enteric coated drugs
  • Route of administration
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11
Q

Explain first pass metabolism

A
  • Drugs absorbed by the GI tract are transported to the liver before being circulated to the rest of the body.
  • The liver will metabolise a lot of the drug before it enters circulation as it sees the drug as a toxin.
  • Often higher concentrations of oral drugs are required to achieve the desired effect.
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12
Q

What is bioavailability ?

A

The extent of metabolism will determine the amount of drug that appears in the circulation to preform its therapeutic task. This is known as bioavailability and is often expressed as a percentage.

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13
Q

Define distribution

A

The transfer of the drug from the general circulation into different organs in the body,

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14
Q

Name 4 factors that effect the distribution of a drug.

A
  • Affinity of the drug for plasma protein.
  • Size, solubility and polarity of the drug.
  • Acidity of drug in solution
  • Blood supply to the tissue
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15
Q

Define excretion

A

The elimination of a drug, usually by the kidneys as urine.

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16
Q

Explain 5 ways drugs can be eliminated

A
  • kidneys as urine (most common)
  • The lungs
  • Exocrine glands (Saliva, breast milk, and tears)
  • The skin
  • The GI tract
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17
Q

Define “half life value”

A

Time it takes for 50% of an administered dosage to be eliminated.

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18
Q

What may increase a drugs half life ?

A

Hepatic disease.

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19
Q

Explain the term therapeutic range.

A

It is necessary to have adequate plasma concentrations of a drug within the plasma to achieve a therapeutic range

Which is why we test for drug “levels”

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20
Q

Define drug potency

A

Absolute amount of drug required to produce an effect

A more potent drug is one that requires lower dose to cause the same effect

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21
Q

What solubility is a polar molecule ?

A

Water soluble

22
Q

What solubility is a non polar molecule ?

A

Lipid soluble

23
Q

What can a polar molecule do ?

A

Travel within the blood stream.

Plasma contains water.

24
Q

What can a non polar molecule do ?

A

Travel through the cell membranes phospholipid bilayer.

25
Q

What can a non polar molecule not do ?

A

Travel within the blood stream by itself due to it “hating water” it has to be carried by a plasma protein.

26
Q

Explain plasma protein binding

A
  • Proteins such as albumin can bind to many drugs
  • Only the drug which is not bound is available to the body
  • If alot of the drug binds to the proteins then there is less drug available.
27
Q

How much warfarin is plasma protein bound ? What does this mean ?

A

Warfarin is 97% plasma protein bound. Only 3% is actually active and may be excreted.

28
Q

Case study

Jack is on warfarin, he has been prescribed sodium valproate. Shortly afterwards, he notices that he bleeds and bruises easier.

A

The sodium valproate displaces the warfarin as it has a stronger plasma protein binding. This means less warfarin is bound to the plasma protein which means there is more warfarin available to the bloodstream. The more warfarin exists as a free drug the more it effects the body, due to warfarin being a blood thinner this is what causes the increase bruising and bleeding.

29
Q

What may effect protein levels within the blood ?

A
  • liver disease - the source of protein production
  • malnutrition - loss of protein
  • anorexia - loss of protein
30
Q

Name the factors that affect plasma protein binding and explain what it means.

A
  • Elderly - reduced protein in the blood
  • Reduction in albumin
  • liver disorders
  • malnutrition/anorexia
  • Other drugs - competition for plasma protein

It means that a given dose of the drug will now have a greater effect as less of the drug is plasma protein bound and therefore a smaller dose may be required.

31
Q

Explain the movement from of an orally administered drug to the systemic circulation.

A
  • absorbed through the small intestines.
  • the drug molecules enter the mesenteric vessels which will drain nutrient rich blood away from the intestines to the liver via the hepatic portal vein.
32
Q

What is acetaminophen more commonly known as ?

A

Paracetamol

33
Q

What is paracetamols bioavailability?

A

88%

34
Q

Explain why morphine sulphate oral dose is 15-30mg where as it’s intravenous dose is 1-10mg (70kg adult male)

A

Morphine sulphates bioavailability is 24% after undergoing first pass metabolism

35
Q

Name a drug that can not be given orally and explain why.

A

GTN (glyceryl trinitrate) undergoes high first pass metabolism so if given orally there would be given no effect of the tablet.

Sublingual administration bypasses first pass metabolism and thereby reaches the blood stream directly.

36
Q

Why is a drugs half life important ?

A

It will inform us how frequently the drug should be administered.

37
Q

What is paracetamols half life ?

A

2 hours

38
Q

What enzymes are present within the liver ?

A

P450 enzymes

39
Q

What do p450 enzymes do to a drug ?

A

Break them down

40
Q

What is a prodrug ?

A

An inactive compound which can be metabolised to become active

41
Q

What should be taken into consideration with pregnant women ?

A

Drug can cross into placenta and breast milk

42
Q

Consideration with children

A

Higher proportion of water
Lower plasma protein level - more available drug
Immature liver/kidney may be metabolised or excreted slower

43
Q

Considerations with older people

A

Body fat increases
Body water decreases
Plasma proteins decrease

44
Q

What medication anti sickness medication can increase gut transit time ?

A

Metoclopramide

45
Q

Explain phase 1 and phase 2 metabolism in terms of asprin

A

Phase 1 - p450 enzymes transfer asprin (inactive ) to salycilic acid (active)

Phase 2 - the drug is transformed to a water soluble drug for excretion

46
Q

Explain phase 1 metabolism

A

Adding or removing functional groups by

  • oxidation ( most common, use cytochrome p450 enzymes)
  • reduction
  • hydrolysis

To increase the polarity of a drug. Can convert a drug to its active metabolite.

46
Q

Explain phase 2 metabolism

A

Known as conjugation, involves the attachment of an ionised group to the drug.

These groups include glutathione, methyl, or acetyl groups.

Makes drugs more water

47
Q

What are the 2 metabolites that can be produced following metabolism ?

A

Active metabolite or inactive metabolite

48
Q

What is an active metabolite ?

A

A drug that retains the same activity as the parent drug eg remains active.

Such as codeine is metabolised into morphine

49
Q

What’s an inactive metabolite.

A

A drug that has no pharmacological activity of the original drug

50
Q

What is a pro drug ?

A

A drug that’s administered as in inactive form which is metabolised to an active form.

51
Q

What drugs can diffuse easily into the placenta ?

A

Drugs with a low molecular weight

Drugs with a high molecular weight are less likely to pass to the placenta

Pharmacology Exam (10 decks)

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