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5: Y5 - ESA 5 - Pharmacology > Pharmacodynamics, Drug Interactions, and Toxicology > Flashcards

Pharmacodynamics, Drug Interactions, and Toxicology Flashcards

1
Q

What are the key concepts of pharmacodynamics?

A
  • Drug concentration and response
  • Affinity
  • Efficacy
  • Potency
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2
Q

What do drugs cause to have their effect?

A
  • Depression
    Stimulation
  • Destruction
  • Replacement
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3
Q

What do most drugs interact with to have their effect?

A

Endogenous proteins

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4
Q

What effect do drugs have on endogenous proteins to have their effect?

A
  • Some activate endogenous proteins
  • Some antagonise, block, or inhibit endogenous proteins
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5
Q

Give some examples of unconventional mechanisms of action of drugs

A
  • Disruption of structural proteins
  • Act as enzymes
  • Covalently linking macromolecules
  • Reacting chemically with small molecules
  • Binding free molecules/atoms
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6
Q

Where might drugs exert their actions?

A
  • Cell surface receptors
  • Nuclear receptors
  • Enzymes (inhibition)
  • Blocking ion channels
  • Inhibiting transport
  • Inhibiting signal transduction proteins
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7
Q

What does plotting a drug effect against concentration produce?

A

A Michaelis-Menten curve, where a rectangular hyperbole is shown as effect increases with concentration, and begins to level out once Emax is almost reached

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8
Q

What will plotting drug effect against logConcentration produce?

A

A sigmoid curve

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9
Q

What happens when a drug binds to a cell receptor?

A

It produces a change

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10
Q

What is a complete agonist able to do?

A

Produce 100% signal as concentration is increased

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11
Q

Can a partial agonist produce 100% signal?

A

No, even when concentration is increased

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12
Q

What do competitive antagonists do?

A

Bind to the receptor at its binding site, therefore blocking the binding of agonist molecules

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13
Q

What happens to the reduction in response as the concentration of competitive antagonist is increased?

A

The reduction in response is also decreased

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14
Q

What can be done to overcome competitive antagonist binding?

A

Increase the concentration of agonist, which can still produce 100% effect

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15
Q

How do non-competitive antagonists work?

A

They bind to the receptor away from their binding site, and act by causing a change in the receptor site, which can either prevent agonist binding, or prevent response once the agonist has bound to the receptor. Either way, this reduces the effect agonists can have

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16
Q

What happens when you increase agonist concentration of agonists with non-competitive antagonists?

A

The maximum level of signal production will stay the same, as the increased concentration will not affect the antagonist binding

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17
Q

Describe the features of an ideal drug, in terms of binding

A

It interacts at only one site, thus causing no unwanted side effects

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18
Q

What is the reality with binding of drugs?

A

They will bind at more than one binding site, and thus cause collateral damage

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19
Q

What is the result of a drug being more selective for its target?

A

It means there is less chance it will interact with different targets, and have less undesirable side effects

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20
Q

Give an example of a selective drug

A

Penicillin - it targets the bacterial cell wall, thus leaving mammalian cells alone, therefore has minimal side effects

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21
Q

What is meant by specificity of the drug?

A

How accurate a drug is at binding to a specific receptor or subtype

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22
Q

Give an example of a class of drugs that has side effects due to lack of specificity

A

Drugs affecting adrenergic receptors, which can cause effect in the heart and lungs

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23
Q

What is affinity?

A

The tendency of a drug to bind to a specific receptor type

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24
Q

What does a high affinity result in?

A

A drug is more likely to cause response at a lower concentration

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25
Q

What is efficacy?

A

The ability of a drug to produce a response as a result of the receptor or receptors being occupied

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26
Q

What does efficacy describe?

A

The maximum effect of a drug

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27
Q

What is potency?

A

The dose required to produce the desired biological response

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28
Q

What does potency describe?

A

The different doses of two drugs required to exact the same effect

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29
Q

What is the therapeutic index?

A

The relationship between concentrations causing adverse effects and concentrations causing desirable effects

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30
Q

How is therapeutic effect calculated?

A

EC50 (adverse effect) / EC50 (desired effect)

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31
Q

What is the therapeutic window?

A

The range of dosages that can effectively treat a condition whilst still remaining safe.

The range between the lowest dose that has a positive effect, and the highest dose before the negative effects outweigh the positive effects

32
Q

At what stage of treatment can drug interactions occur?

A

Any stage, from prescription to excretion

33
Q

What factors can affect how a drug interacts?

A
  • Age
  • Genetics
  • Pathology
  • Other factors
34
Q

What happens to the probability of drug interactions with increasing number of drugs taken by a patient?

A

It increases

35
Q

What might drugs affect that could cause pharmacokinetic drug-drug interactions?

A
  • Absorption
  • Distribution
  • Metabolism
36
Q

How might drugs affect absorption?

A

Some drugs can change gut motility

37
Q

Give two examples of drugs that reduce gut motility

A
  • Opiates
  • Atropine
38
Q

What effect on secondary drug pharmacokinetics might reduced gut motility have?

A
  • Reduced Cmax (peak serum concentration)
  • Increased Tmax (time spent at Cmax)
39
Q

Why does reduced gut motility lead to a reduced Cmax of the secondary drug?

A

Slower absorption of a secondary drug

40
Q

Why does reduced gut motility lead to increased Tmax of the secondary drug?

A

The secondary drug will spend longer in the gut, meaning that although it is absorbed at a slower rate, it is absorbed for longer

41
Q

Why might a reduction in Cmax and increase in Tmax of the secondary drug cause adverse effects?

A

Due to it not reaching an effective Cmax and having no effect, or exerting effects for too long due to high Tmax

42
Q

Give an example of a drug that can increase gut motility

A

Metoclopramide

43
Q

What effect might an increase in gut motility have on the pharmacokinetics of the secondary drug?

A
  • Increased Cmax
  • Reduced Tmax
44
Q

Why does increased gut motility reduce Cmax of the secondary drug?

A

As it is absorbed faster

45
Q

Why does increased gut motility lead to reduced Tmax of the secondary drug?

A

As the drug will move through the gut faster, not allowing all of it to be absorbed

46
Q

What is volume of distributino?

A

A measure of how widely a drug is distributed in body tissues

47
Q

GIve 7 examples of inducers of the cytochrome P450 system

A
  • Phenytoin
  • Carbamazepine
  • Barbiturates
  • Rifampicin
  • Alcohol
  • Sulphonylureas
  • St. John’s Wort
48
Q

Give 9 examples of inhibitors of the cytochrome P450 system

A
  • Omeprazole
  • Disulpfiram
  • Erythromycin
  • Valproate
  • Isoniazid
  • Cimetidine
  • Ciprofloxacin
  • Ethanol
  • Sulphonamides
49
Q

What effect does a falling GFR (acute or chronic) have on drugs?

A

Leads to reduced clearance of renally excreted drugs

50
Q

What effect does disturbances of electrolytes have on drugs?

A

May predispose patients to toxicity, especially potassium

51
Q

What kind of drugs will damage kidney functions?

A

Nephrotoxins

52
Q

What is the result of hepatic disease on drugs?

A

There is reduced clearance of hepatically metabolised drugs, leading to reduced CYP450 activity and longer half life, which can lead to toxicity

53
Q

What happens when opiates are given in cirrhosis?

A

The opiates accumulate over time, leading to a coma

54
Q

What effect can falling cardiac output have on drugs?

A
  • Excessive response to hypotensive agents
  • Reduced organ perfusion
55
Q

What effect does reduced organ perfusion have on drugs?

A

Reduces hepatic and renal blood flow, therefore reduces clearance

56
Q

What is an adverse drug reaction?

A

An unwanted or harmful reaction which occurs after administration of a drug or drugs, and is suspected or known to be due to the drug(s)

57
Q

What are the types of adverse drug reactions?

A
  • Augmented pharmacological effects
  • Bizarre effects
  • Chronic effects
  • Delayed effects
  • End-of-treatment effects
58
Q

What are augmented pharmacological effects?

A

Adverse effects that are known to be occur from the pharmacology of the drug, and are dose-related

59
Q

Give an example of an augmented pharmacological effect

A

Hypoglycaemia due to insulin injection

60
Q

Describe the outcome of augmented pharmacological effects?

A

Rarely fatal

61
Q

What are bizarre adverse effects?

A

Adverse effects that occur unpredictably

62
Q

Desribe the outcome of bizarre adverse effec

A

They have a high morbidity and morality, but are uncommon

63
Q

What are chronic adverse effects?

A

Adverse effects that only occur during prolonged treatment, and not with single doses

64
Q

Give an example of a chronic adverse effect

A

Iatrogenic Cushing’s syndrome with prednisolone

65
Q

What are delayed adverse effects?

A

Adverse effects that occur remote from the treatment, either in the children of treated patients or in patients themselves, years after treatment

66
Q

Give an example of a delayed adverse effect

A

Second cancers in those treated with alkylating agents for Hodgkins disease

67
Q

What are end-of-treatment adverse effects?

A

Adverse effects that occur when a drug is stopped, especially when it is stopped suddenly

68
Q

Give an example of an end-of-treatment adverse effect

A

Unstable angina after ß-adenoceptor agonists are suddenly stopped

69
Q

What are the risk factors for ADRs?

A
  • Ignorant, inappropriate, or reckless prescribing
  • Polypharmacy
  • Patients at extremes of age
  • Multiple medical problems
  • Use of drugs with narrow therapeutic indices
  • Drugs being used near their minimum effective concentration
70
Q

Why are patients at extremes of age at increased risk of ADRs?

A
  • Altered PK profile
  • Possible co-morbidities
71
Q

What is considered to be a mild ADR?

A

Trivial or unnoticable

72
Q

What is considered to be a mild ADR?

A

Requiring additional treatment

73
Q

What is considered to be a major ADR?

A

Requiring additional treatment

74
Q

What scheme is used to report adverse drug events?

A

Yellow card scheme

75
Q

How does the yellow card scheme work?

A
  • Severe events are reported for established drugs
  • Any event is reported for new and emerging drugs

5: Y5 - ESA 5 - Pharmacology (28 decks)

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