Drugs Flashcards

1
Q

What is absorption?

A

Process of movement of the unchanged drug from the site of administration to the systemic circulation

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2
Q

What is Cmax?

A

Drug concentration peak

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3
Q

What is Tmax?

A

The time at which Cmax us observed

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4
Q

What is bioavailability?

A

The amount of the drug available for action in the systemic circulation

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5
Q

What factors affect bioavailability?

A

Formulation
Ability of drug to pass physiological barriers
GI effects
First pass metabolism

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6
Q

What are some physiological barriers drugs encounter?

A

Lipid solubility
pH
Ionisation

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7
Q

How does ionisation affect drug diffusion?

A

An ionised drug will not cross the cell membrane

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8
Q

What is the Henderson-Hasselbalch equation used to show?

A

The relationship between local pH and the degree of ionisation

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9
Q

What is the Henderson-Hasselbalch equation?

A

pH=pKa+log10([A-]/[HA])

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10
Q

What is the lipid water partition coefficient?

A

The ratio of the amount of drug which dissolves in the lipid and water phase when they are in contact

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11
Q

How does lipid solubility affect diffusion across a membrane?

A

A drug must be lipid soluble to diffuse across a membrane

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12
Q

By what methods can drugs pass across the membrane?

A
Passive diffusion
Filtration
Bulk flow
Active transport
Facilitated diffusion
Ion pair transport
Endocytosis
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13
Q

What drugs cross the membrane via facilitated diffusion?

A

Monosaccharides, amino acids, vitamins

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14
Q

What is the driving force for filtration, bulk flow and pore transport?

A

The difference in hydrostatic or osmotic pressure

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15
Q

What gastrointestinal factors affect drug absorption?

A

Motility
Food
Illness

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16
Q

What is first pass metabolism?

A

Metabolism of drug prior to it reaching the systemic circulation

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17
Q

What are the 4 primary systems that affect first pass metabolism?

A

GI lumen
Gut wall enzymes
Bacterial enzymes
Hepatic enzymes

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18
Q

What are the benefits of subcutaneous and IM administration?

A

Only a small volume required
Avoids first pass metabolism
Water soluble drugs absorbed well

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19
Q

What are the benefits of buccal and sublingual administration?

A

Avoids first pass metabolism

Enter circulation directly

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20
Q

What are the benefits and disadvantages of suppositories?

A

Avoids first pass metabolism
Can be used for drugs that irritate stomach
Absorption tends to be slow

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21
Q

What are the benefits of inhalation of drugs?

A

Can be used for volatile agents
Relatively rapid action
Can be used for topical or systemic effects

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22
Q

What are the advantages and disadvantages of transdermal administration?

A

Avoids first pass metabolism
Controlled release
Few substances well absorbed
Needs to be nonirritant

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23
Q

What is drug distribution?

A

Reversible transfer of a drug between the blood and extravascular fluids and tissues of the body

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24
Q

What factor affect tissue distribution?

A
Plasma protein binding
Tissue perfusion
Membrane characteristics
Transport mechanisms
Diseases and other drugs
Elimination
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25
Q

What is the effect of plasma protein binding?

A

Only unbound drugs are biologically active

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26
Q

What factors affect the amount of a drug that binds to plasma proteins?

A
Renal failure
Hypoalbuminaemia
Pregnancy
Other drugs
Saturability of binding
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27
Q

What is the apparent volume of distribution (Vd)?

A

Theoretical volume that would be necessary to contain the amount of the administered drug at the same concentration as it is in the plasma

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28
Q

What is the correlation between Vd and the ability of a drug to diffuse?

A

The higher the Vd, the better the drug is at diffusing

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29
Q

What is clearance?

A

The theoretical volume from which a set amount of a drug is completely removed over time

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30
Q

What is drug clearance dependent on?

A

Urine flow rate for renal clearance

Metabolism and biliary secretion for hepatic clearance

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31
Q

What is half life (t1/2)?

A

Time taken for the drug concentration in the blood to half

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32
Q

What is the half life dependent on?

A

Volume of distribution and rate of clearance

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33
Q

What does prolongation of the half life cause?

A

Toxicity

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34
Q

When is steady state reached in chronic administration?

A

Usually after approx 4 half lives

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35
Q

What is elimination?

A

Removal of the active drug and its metabolites from the body

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36
Q

What are the 3 stages of drug elimination?

A

Metabolism and excretion

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37
Q

Where does most of drug metabolism take place?

A

Liver

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38
Q

What is the primary organ of drug excretion?

A

Kidneys

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39
Q

What are the 3 principle mechanisms of drug excretion?

A

Glomerular filtration
Passive tubular reabsorption
Active tubular secretion

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40
Q

What drugs are filtered during glomerular filtration?

A

All unbound drugs, as long as they size, charge or shape are not excessively large

41
Q

What happens in active tubular secretion?

A

Acidic and basic compounds are actively secreted into the proximal tubule

42
Q

Why is active tubular secretion important?

A

Eliminating protein bound cationic and anionic drugs

43
Q

What is the process of passive tubular reabsorption?

A

As the filtrate moves down the renal tubule, any drug present is concentrated and passive diffusion allows some of the drug to diffuse across the membrane back into circulation

44
Q

Where does passive tubular reabsorption tale place?

A

Distal tubule and collecting duct

45
Q

What is biliary secretion?

A

Secretion of the drug into the bile where it can then be reabsorbed into the enter-hepatic circulation

46
Q

What does metabolism in the liver lead to and what does this cause?

A

Conjugation of the drug

Cannot be reabsorbed into the circulation

47
Q

What ways are drugs delivered to patients?

A
Tablets or capsules
Solutions or suspensions
Ointments and creams
Inhalation
Injections
Suppositories
Pessaries
48
Q

Why are there different drug formulations?

A

To allow selective targeting, avoid pre or systemic metabolism, allow for fast or slow release

49
Q

Where are oral medications absorbed?

A

GI tract

50
Q

Who are solutions or suspensions used for?

A

Young, old, those with difficulty swallowing

51
Q

What is the rate limiting step in absorption of tablets?

A

Break down of the tablet

52
Q

What are the advantages of tablets and capsules?

A
Convenient
Accurate dose
Reproducability
Drug stability
Ease of mass production
53
Q

What are enteric coated tablets?

A

A drug with a protective coating to protect the drug from the stomach and the stomach from the drug

54
Q

Why are prolonged or delayed release formulations useful?

A

Most conditions require prolonged therapy
Maintains drug levels within therapeutic range
Reduces need for frequent dosing
Improved compliance

55
Q

What are prodrugs?

A

Synthesised inactive derivatives of an inactive drug which requires to be metabolically activated after administration

56
Q

What are buccal and sublingual administration ideal for?

A

Drugs with extensive first pass metabolism

57
Q

Who is the rectal route useful for?

A

Young, old, patients unable to swallow

58
Q

What can the rectal route be used to treat?

A

Local conditions, or systemic absorption

59
Q

What are pessaries used for?

A

To treat local conditions

60
Q

What are the 3 forms of injection based administration?

A

IV
IM
Subcutaneous

61
Q

When is IV used?

A

When rapid onset of action id required
Careful control of plasma levels required
Drug has short half life

62
Q

How can IV be given?

A

Rapidly
Slowly- to prevent toxic effects
Continuoisly- ensure accurate controls of plasma levels

63
Q

What does IM allow for?

A

More sustained duration of action

64
Q

What are subcutaneous injections used to administer?

A

Insulin
Heparin
Narcotic analgesics

65
Q

What are 2 types of subcutaneous administration?

A

Dermojet

Pellet implantation

66
Q

Why is subcutaneous injection uses?

A

Bypasses need for venous access

Slow absorption

67
Q

What is transdermal drug delivery?

A

Adhesive patched containing the drug are applied to the skin, drug crosses the surface by diffusion and goes into systemic circulation

68
Q

What is the benefit of transdermal drug delivery?

A

Bypasses first hepatic inactivation

69
Q

What can percutaneous drugs be used for?

A

Local or systemic

70
Q

Give an example of a systemic percutaneous drug?

A

Transderm-SCOP

71
Q

Give an example of a local percutaneous drug?

A

Hydrogel transdermal patch

72
Q

How can inhalation drugs be administered?

A

Pressurised aerosol, breath activated aerosol, nebuliser, dry powder device

73
Q

What are the advantages of inhalation?

A
Delivered directly to site of action
Rapid effect
Small doses uses
Little systemic absorption
Reduced adverse effects
74
Q

What are the 3 types of carrier based drug delivery?

A

Monoclonal antibodies
Liposomal drug delivery
Nanoparticle based drug delivery

75
Q

How do monoclonal antibodies work as a carrier based drug delivery system?

A

Modified antibodies with attached toxins cytokines etc act directly when binding to a cancer specific antigen and induce immunological response

76
Q

How does a liposomal drug delivery system work?

A

Allows for drug accumulation at disease sites and avoidance of sensitive sites

77
Q

How do nanoparticles work as a carrier based drug delivery system?

A

Drug can be targeted to precise location, making the drug more effective and reduce side effects

78
Q

What are the 3 types of nano carriers?

A

Nanoparticle
Nanotubule
Nanoshell

79
Q

What are carbon nanotubes used to treat?

A

Bronchial asthma

80
Q

What are gold nano tubules used to treat?

A

Chemo

81
Q

What are nanoerythrosomes and what are they used for?

A

Resealed erythrocytes that carry proteins, enzymes and macromolecules
Used in treatment of liver tumour and enzyme and pancreatic diseases

82
Q

What is an adverse drug reaction?

A

Any response to a drug which is harmful, unintended and occurs in doses used for prophylaxis, diagnosis or treatment

83
Q

What are the classifications of onset of adverse drug reactions?

A

Acute- within 60 minutes
Sub-acute- 1-24 hours
Latent- >2days

84
Q

What are the classifications of severity of adverse drug reactions?

A
Mild= bothersome but requires no change in treatment
Moderate= Requires change in therapy, additional treatment, hospitalisation
Severe= Disabling, life threatening
85
Q

What are the classifications of adverse drug reactions?

A
Augmented
Bizarre
Chronic
Delayed
End of treatment
Failure of treatment
86
Q

What is a type A drug reaction?

A

Augmented
Dose related and predictable
Resolve when drug is reduced or stopped

87
Q

What causes a type A drug reaction?

A

Too high a dose
Pharmaceutical variation
Pharmacokinetic variation
Pharmacodynamic variation

88
Q

What is a type B drug reaction?

A

Bizarre
Rare and unrelated to dose
Can cause serious illness

89
Q

What causes a type B drug reaction?

A

Immunological or genetic response

90
Q

When are type B drug reactions more common?

A

With macromolecules
Patients with history of asthma or eczema
Presence of leukocyte antigen
Sex linked G6P deficiency

91
Q

What is a type C drug reaction?

A

Chronic
Does not occur with single dose
Semi predictable

92
Q

What is a type D drug reaction?

A

Delayed

Occur in children of patients or patients years after end of treatment

93
Q

What are some examples of type D drug reactions?

A

Second cancers in those treated with alkylating agent or immunosuppressants
Graniofacial malformations in children of those treated with isotrtinoin

94
Q

What is a type E drug reaction?

A

End of treatment

Adverse reaction when treatment is stopped, particularly when it was stopped suddenly

95
Q

What are some examples of type E drug reactions?

A

Unstable angina or MI when taken off beta blockers

Withdrawal seizures when taken off anti-epileptics

96
Q

What are type F drug reactions?

A

Failure of treatment
Common and dose related
Frequently caused by drug interactions

97
Q

What are the 4 steps in diagnosis a type F drug reaction?

A

Differential diagnosis
Medication history
Assess time of onset and dose relationship
Lap investigations

98
Q

What are the risk factors of adverse drug reactions?

A
Age
Multiple medications
Inappropriate medication prescribing, use or monitoring
End organ dysfunction
Altered physiology
History of adverse drug reactions
Dose and duration of exposure
Genetic predisposition