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Exam Prep MCQs > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

Can partial agonists act as both agonists and antagonists?

A

Yes, when given in isolation can act as agonists or as antagonists when given in combination with a full agonist.

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2
Q

What intrinsic activity do partial agonists have?

A

Full agonists have intrinsic activity of 1

Partial agonists have intrinsic activity of <1

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3
Q

Is buprenorphine an agonist or antagonist?

A

Partial agonist

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4
Q

Is pentazaocine an agonist or antagonist?

A

Mixed agonist-antagonist

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5
Q

Is clozapine an agonist or antagonist?

A

Partial agonist at D2 receptors

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6
Q

What are antagonists?

A
  • they have affinity but intrinsic activity of zero
  • can act as agonists at some receptors and antagonists at others (mixed agonists-antagonists eg pentazocine)
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7
Q

What do competitive antagonists do?

A
  • Cmax remains the same
  • dose response curve shifted to right
  • compete for a receptor with agonists
  • overcome by increasing agonist dose
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8
Q

How does non-competitive antagonism affect Cmax?

A

Reduces Cmax

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9
Q

What is the effective concentration 50?

A

The drug concentration that induces a response halfway between zero amd maximum.

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10
Q

What is the ED50?

A

The dose or amount of drug that produces a therapeutic response or desired effect in 50% of the subjects taking it.

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11
Q

What is the therapeutic index?

A

Lethal dose 50 / Effective Dose 50

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12
Q

How is the log dose-response curve affected by the addition of a competitive antagonist?

A

Shifted to the right as a higher dose of agonist is required to produce an equivalent response

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13
Q

What represents potency on the log dose-response curve?

A

The position of the ED50, much like the position of P50 on the oxyHb dissociation curve

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14
Q

What subunits do G proteins consist of?

A

Alpha, beta and gamma subunits

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15
Q

What kind of receptor are insulin receptors?

A

Tyrosine kinase

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16
Q

What kind of receptors are opioid receptors?

A

G-protein coupled

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17
Q

Is cAMP hydrophobic?

A

No. Hydrophilic.

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18
Q

Does nitric oxide act via cAMP?

A

No, cGMP

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19
Q

Does ranitidine have agonist properties?

A

No.

H2 receptor antagonist.

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20
Q

Does prazosin have agonist properties?

A

No. It is a selective alpha1-adrenoreceptor blocker.

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21
Q

Does pindolol have agonist properties?

A

Yes.

Non-selective beta-blocker with partial beta-agonist activity.

It also has partial agonist/antagonist activity at the 5-HT1A receptor.

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22
Q

Does naltrexone have agonist properties?

A

No.

It is an opioid receptor antagonist.

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23
Q

What is Xameterol?

A

It is a mixed beta-agonist/antagonist.

It has agonist and antagonist properties.

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24
Q

List mixed agonist-antagonists.

A

Drugs that exert both agonistic and antagonistic properties. Such as:

  • opioid (pentazocine, nalbuphine, buprenorphine)
  • mirtazepine
  • pindolol
  • xameterol
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25
Q

In a negative exponential process, what happens to the rate of decay?

A

The rate of decay decreases with increasing time

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26
Q

What is the rate of change of a variable proportional to in an exponential process?

A

The rate of change of a variable is proportional to the magnitude of the variable at that moment in time

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27
Q

Which is longer - the half time or time constant?

A

The time constant is longer.

An exponential process is complete after 3 time constants or 5 half lifes.

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28
Q

How do the time constant and the rate constant relate to each other?

A

The time constant is the reciprocal of the rate constant

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29
Q

How is a negative exponential process converted to a straight line?

A

Semi-log plot

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30
Q

What is the time constant?

A

The time for the process to complete if the rate continued at it’s intitial speed.

It can also be defined as the time taken for an exponential process to fall to 37% or 1/e of it’s previous value.

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31
Q

What is affinity?

A

The ability of a ligand to bind to a specific receptor.

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32
Q

Where do thyroid hormones bind?

A

To intracellular receptors

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33
Q

What subunits does the ACh receptor have?

A
  • 2 alpha subunits (ACh binds here)
  • beta subunit
  • delta subunit
  • epislon subunit (gamma in the foetus)
34
Q

Where does midazolam act?

A

GABAa receptors

35
Q

What type of receptors are nicotinic receptors?

A

Type 1. Membrane bound ligand gated ion channels.

36
Q

What are the strongest to weakest chemical bonds?

A

Ionic > covalent > hydrogen > van der waals

37
Q

What is an ionic bond?

A

Electrostatic forces of attraction between oppositely charged ions after the complete loss or gain of electrons.

38
Q

What are covalent bonds?

A

Involve sharing of electrons in order to gain full outer electron shells.

39
Q

What is hydrogen bonding?

A

Forces of attraction between the positively charged nucleus of a hydrogen atom and an electronegative atom.

40
Q

What are Van der Waals forces?

A

Forces of attraction/repulsion between electron clouds (no definite shape, any moment one part may be positively or negatively charged than the other)

41
Q

Does cAMP mediate decreased HR?

A

No, Beta1 adrenoreceptors are G-protein coupled - stimulation causes increased cAMP and tachycardia

42
Q

Does cAMP mediate liver carbohydrate metabolism?

A

Yes.

Beta2 adrenoreceptors are G-protein coupled, and stimulation causes increased cAMP and glycogenolysis (also increases insulin and glucagon secretion).

43
Q

Is increased contractility mediated by cAMP?

A

Yes.

Beta1 adrenoreceptors are G protein coupled and their stimulation causes increased cAMP and subsequent increase in contractility.

44
Q

Is triglyceride breakdown mediated by cAMP?

A

Yes.

Beta2 adrenoreceptors are G-protein coupled and their stimulation causes increased cAMP and subsequent lipolysis (also increases insulin and glucagon secretion).

Beta3 adrenoreceptors are also G-protein coupled and increase cAMP - they help regulation of lipid metabolism.

45
Q

Is smooth muscle relaxation mediated by cAMP?

A

Yes.

Beta2 adrenoreceptors are G-protein coupled and their stimulation causes increased cAMP and subsequent smooth muscle relaxation.

46
Q

What is volume of distribution?

A

The volume that a drug distributes into following administration

47
Q

Can VoD be larger than total body water?

A

Yes.

TBW = 42L while VoD can be up to 1000L

48
Q

What is VoD measured in?

A

L/kg

49
Q

Is Vod constant for a given drug?

A

Yes

50
Q

What is the calculation for clearance?

A

Vd = clearance x time constant

51
Q

What is a decrement time?

A

The time taken of the plasma level for a drug to fall to a specified value

52
Q

How do decrement time and context sensitive half time relate to each other?

A

Decrement time is the time taken for the plasma level for a drug to fall to a specified value - context sensitive half time is 50%

53
Q

What is the relationship between context sensitive half time and elimination half life?

A

No relationship

54
Q

What is context sensitive half time?

A

The context is the duration of drug infusion - it is the time taken for the plasma levels to fall to 50% of the value when the infusion is stopped.

55
Q

What does CSHT reflect?

A

It reflects the combined effects of distribution and metabolism

56
Q

What affects the VoD?

A
  • regional blood flow
  • lipid solubility
  • degree of tissue protein binding
  • degree of plasma protein binding
  • degree of ionisation
57
Q

How many half lives does it take to reach steady state concentration?

A

5 half lives

58
Q

What is steady state volume of distribution dependent on?

A

Lipid solubility and clearance

59
Q

In infusion kinetics, what is the calculation for loading dose?

A

Loading dose = Vd x desired plasma concentration

60
Q

How do you calculate the maintenance dose in infusion kinetics?

A

Maintenance dose = steady state concentration x clearance

61
Q

In infusion kinetics at a steady state, what is clearance equal to?

A

Clearance = Input (mg/min) / plasma concentration (mg/ml)

(input = clearance x plasma concentration)

INPUT = ELIMINATION at steady state

62
Q

Which P450 enzyme is involved in metabolism of paracetamol?

A

CYP2E1

63
Q

What is CYP3A4 involved in the metabolism for?

A

Midazolam and alfentanil

64
Q

Where is CYP2E1 found and what is it involved in metabolising?

A

It’s found in the kidneys.

It’s involved in the metabolism of fluoride containing volatile agents.

65
Q

What do cytochrome P450 enzyme isoforms account for most of?

A

Most phase 1 reactions

66
Q

Which out of the following are enzyme inducers?

(rifampicin, metronidazole, acute alcohol use, carbamazepine, chloramphenicol)

A

Rifampicin and carbamazepine

(chronic alcohol is an inducer)

67
Q

Which out of the following are enzyme inhibitors?

(rifampicin, metronidazole, acute alcohol use, carbamazepine, chloramphenicol)

A

Metronidazole, acute alcohol use and chloramphenicol

68
Q

What are phase 1 reactions?

A

Oxidation

Hydrolysis

69
Q

What are Phase 2 reactions?

A

Acetylation

Sulphation

Glucuronidation

70
Q

In what ways can elimination happen in kinetics?

A
  • distribution
  • metabolism
  • excretion
71
Q

In 1st order kinetics, is half life constant?

A

Yes

72
Q

In 1st order kinetics, is a constant amount of drug eliminated per unit time?

A

No, a constant proportion is eliminated per unit time

73
Q

Is zero order kinetics a linear process?

A

It is also known as non-linear kinetics

74
Q

In zero order kinetics, how does administering an increased dose affect half life?

A

Half life increases with dose administered

75
Q

Will a drug with a high extraction ratio be affected by protein binding?

A

No and is not affected by enzyme level.

76
Q

Why is lignocaine not an example of an enzyme limited drug?

A

Lignocaine has a high extraction ratio (>0.7) and is therefore flow/perfusion limited (as opposed to enzyme/capacity limited)

77
Q

Does a high extraction ratio imply significant 1st pass metabolism?

A

Yes, most of the drug is extracted on the first pass through the liver, hence why changes in hepatic blood flow can drastically affect clearance.

78
Q

What will affect drugs with a low extraction ratio?

A

Enzyme induction/inhibition can profoundly affect the clearance as these are enzyme/capacity limited drugs

79
Q

What kind of hepatic clearance does warfarin undergo? What other drugs are this kind?

A

It is an enzyme limited drug.

As are phenytoin, theophylline and most benzodiazepines and barbituates.

80
Q

What is the bioavailability of glycopyrrolate?

A

< 5 %

81
Q

Is bioavailability influenced by genetics or circadian rhythm?

A

Yes

82
Q
A

Exam Prep MCQs (19 decks)

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