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Principles > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

What is pharmacodynamics?

A

The effect a drug has on the body- biological effects and mechanism of action)

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2
Q

What is pharmacokinetics?

A

What the body does to a drug (absorption, distribution, metabolism/excretion)

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3
Q

What do drugs act by binding to?

A

Specific target molecules

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4
Q

What do receptors do?

A

Mediate the action of hormones and neurotransmitters

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5
Q

What is an agonist?

A

A drug that binds to a receptor to produce a cellular response

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6
Q

What is an antagonist?

A

A drug that blocks the action of an agonist

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7
Q

What do agonists possess?

A

Efficacy and affinity

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8
Q

What is affinity?

A

The strength of association between a ligand and receptor

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9
Q

What is efficacy?

A

The ability of an agonist to produce a cellular response

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10
Q

What do antagonists possess?

A

Affinity not efficacy

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11
Q

What does increasing agonist concentration do?

A

Increases the number of receptors occupied

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12
Q

What is EC50?

A

The concentration of agonist that elicits a half maximal response

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13
Q

What is a full agonist?

A

Produce a maximal response

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14
Q

In terms of a graph of agonist concentration against response, what direction would the curve move for increased/decreased potency?

A

Shifting left for increased potency and right for decreased potency

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15
Q

In terms of a graph of agonist concentration against response, what would a taller curve show in terms of efficacy?

A

Increased efficacy

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16
Q

What is competitive antagonism?

A

Binding of agonists and antagonists at the same binding site and therefore is competitive (whichever binds first will elicit a response)

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17
Q

What is non-competitive antagonism?

A

The agonist and antagonist bind to different sites so it is not competitive

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18
Q

Can the agonist and antagonist bind at the same time?

A

They can bind at the same time- but activation cannot occur when the antagonist is bound

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19
Q

What does antagonist binding in non-competitive antagonism do?

A

Depresses the maximum response

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20
Q

What is potency?

A

The amount of a drug required to produce a given response (smaller potency is best)

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21
Q

What are the 4 main factors involved in drug movement through the body?

A

Absorption, distribution, metabolism, excretion

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22
Q

What 4 factors does drug absorption depend on?

A

Solubility, chemical stability, lipid to water partition coefficient, degree of ionisation

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23
Q

What is the relationship between rate of diffusion and lipid solubility?

A

As one increases, the other increases

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24
Q

What can unionised drugs do that ionised ones can’t?

A

Diffuse across the lipid bilayer

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25
Q

What is the pKa?

A

pH at which half a drug is ionised and half isn’t

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26
Q

When is an acid ionised?

A

pH>pKa

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27
Q

When is a base ionised?

A

pH

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28
Q

How is pKa worked out for an acid?

A

pH-pKa= log(AH/A-)

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29
Q

How is pKa worked out for a base?

A

pH-pKa= log (BH+/B)

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30
Q

Where does the absorption of weak acids take place?`

A

Stomach lumen

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31
Q

Where does absorption of bases occur?

A

Small intestine

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32
Q

Why does most absorption occur in the small intestine?

A

Large surface area

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33
Q

Which is absorbed better, weak or strong acids/bases?

A

Weak

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34
Q

What factors affect GI absorption?

A

GI motility, blood supply, pH, physiochemical interactions, presence of transporters, how drug is manufactured

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35
Q

What is oral availability?

A

The fraction of a drug that reaches the systemic circulation after oral ingestion

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36
Q

What is systemic availability?

A

The fraction of a drug that reaches the systemic circulation after absorption

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37
Q

What drugs have 100% systemic availability?

A

IV

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38
Q

What are disadvantages of oral drugs?

A

Some can be inactivated by enzymes/acid, GI irritation, difficulty swallowing

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39
Q

What is an advantage of sublingual administration?

A

Bypasses the portal system and first pass metabolism

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40
Q

When is rectal administration used?

A

Nocturnally or when oral is compromised

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41
Q

What are disadvantages of giving drugs IV?

A

Must be sterile, risk of sepsis and embolism

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42
Q

What are the disadvantages of intramuscular administration?

A

Painful, tissue damage, variable absorption

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43
Q

What is an advantage of intramuscular administration?

A

Rapid onset of lipid soluble drugs

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44
Q

What type of drugs are able to move between fluid compartments?

A

Free drugs

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45
Q

What can ionised/unionised drugs not bound to proteins do?

A

Move freely

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46
Q

What drugs move by diffusion?

A

Only unionised drugs

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47
Q

What type of drugs can move out of the plasma?

A

Those that are not bound

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48
Q

What is the apparent volume in which a drug is dissolved known as?

A

Volume of distribution (Vd)

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49
Q

How is Vd worked out?

A

amount of drug in body/plasma concentration

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50
Q

What does a Vd < 10 mean?

A

Drug is mainly contained in the vascular compartment

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51
Q

What does a Vd between 10 and 30 mean?

A

Drug is largely restricted to extracellular fluid

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52
Q

What does a Vd > 30 mean?

A

There is distribution throughout total body water or accumulation in certain tissues

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53
Q

What is the concentration a drug must reach to achieve an effect known as?

A

Minimum effective concentration

54
Q

What is the concentration at which a drug causes significant unwanted effects known as?

A

Maximum tolerated concentration

55
Q

Where does the ideal drug concentration lie?

A

Between the minimum effective concentration and maximum tolerated concentration

56
Q

What is the difference between the MEC and MTC known as?

A

Therapeutic ratio

57
Q

What is significant about having a greater therapeutic ratio?

A

It means the drug is safer

58
Q

How is the therapeutic ratio worked out?

A

MTC/MEC

59
Q

What is first order kinetics?

A

The rate of drug elimination is directly proportional to the drug concentration

60
Q

How does a graph of first order kinetics fall?

A

Exponentially

61
Q

What is the half life of a drug?

A

The time taken for drug concentration to fall by 50%

62
Q

What does doubling the concentration of a drug NOT do?

A

Change the half life

63
Q

What does doubling the concentration of a drug do to the duration of the drug?

A

Doubles it

64
Q

What is clearance?

A

The volume of plasma cleared of a drug in unit time

65
Q

What does clearance apply to?

A

Drugs with first order kinetics

66
Q

How do you work out the rate of elimination?

A

Clearance x plasma conc

67
Q

What are the units of clearance?

A

l/hr

68
Q

What does clearance determine?

A

The maintenance dose rate

69
Q

What is the maintenance dose rate?

A

Dose per unit time required to maintain a given plasma concentration

70
Q

When is steady state concentration reached?

A

After approx. 5 half lives

71
Q

What is an initial dose of a drug given at the beginning of a course of treatment before stepping down to a lower maintenance dose known as?

A

The loading dose

72
Q

What is the relationship between clearance and half life?

A

Shorter clearance= faster half life

73
Q

What is meant by zero order kinetics?

A

Drugs are eliminated at a constant rate rather than proportional to their concentration

74
Q

What two different ways can drugs be excreted in urine?

A

Unchanged, highly charged molecules or chemically transformed compounds rendered more polar by metabolism

75
Q

Why are drugs rendered more polar before excretion?

A

So they are not reabsorbed by the kidneys

76
Q

What other ways can drugs be excreted besides urine?

A

Bile, and minor ways are through sweat or milk

77
Q

What organs are involved in drug metabolism?

A

Primarily the liver but also the GI tract, lungs and plasma

78
Q

What is phase 1 of drug metabolism?

A

Catabolic- oxidation/reduction/hydrolysis occurs to make drugs more polar. Adds a chemical group to permit conjugation

79
Q

What is phase 2 of drug metabolism?

A

Anabolic- conjugation, adds an endogenous compound which increases polarity

80
Q

In terms of metabolism, if a drug is already polar what can it do?

A

Skip straight to phase 2 metabolism

81
Q

Are all drugs excreted polar?

A

No some are excreted unchanged

82
Q

Where does oxidation of lipid soluble drugs take place?

A

Haem proteins in the endoplasmic reticulum of liver hepatocytes and elsewhere

83
Q

What are the superfamily of haem proteins classified on the basis of and what are they known as?

A

CYP proteins- amino acid sequence similarities

84
Q

What does the first number after CYP signify?

A

Gene family

85
Q

What does the first letter after CYP signify?

A

Gene subfamily

86
Q

What does the second number after CYP signify?

A

Individual gene

87
Q

What are the main gene families in the liver?

A

CYP1, 2 and 3

88
Q

What subfamily do 50% of prescribed drugs come from?

A

CYP3A

89
Q

What does a drug enter the complex monooxygenase P450 cycle as?

A

Drug substrate (RH)

90
Q

What are two atoms of oxygen provided via to the dug substrate in the monooxygenase P450 cycle?

A

Molecular oxygen O2

91
Q

What happens to the first oxygen atom in the monooxygenase P450 cycle?

A

Added to the drug to yield the hydroxyl product (ROH) which leaves the cycle

92
Q

What happens to the second oxygen atom in the monooxygenase P450 cycle?

A

Combines with hydrogen to form H2O

93
Q

What do phase 2 reactions usually result in?

A

Inactive products

94
Q

Where do phase 2 reactions largely occur?

A

The liver

95
Q

What is glucuronidation?

A

Common reaction in phase II involving transfer of glucuronic acid to electron rich atoms of the substrate

96
Q

What are examples of endogenous substances subject to glucuronidation?

A

Bilirubin, adrenal corticosteroids

97
Q

What is the ANS responsible for?

A

Carrying output from the CNS to the whole of the body except skeletal muscle

98
Q

What are some involuntary visceral functions of the ANS?

A

Contraction/relaxation of smooth muscle, all exocrine and some endocrine secretions, heartbeat, some metabolism

99
Q

What does the parasympathetic system coordinate?

A

The body’s basic homeostatic function

100
Q

What does the sympathetic system coordinate?

A

The body’s response to stress

101
Q

Describe the outflow and ganglionic fibre of the sympathetic system?

A

Thoracolumbar outflow- short preganglionic, long postganglionic

102
Q

Describe the outflow and ganglionic fibre of the parasympathetic system?

A

Craniosacral- long preganglionic and short postganglionic

103
Q

What is the postganglionic neurotransmitter in the sympathetic system?

A

Usually noradrenaline

104
Q

What is the postganglionic neurotransmitter in the parasympathetic system?

A

Acetylcholine

105
Q

What is the preganglionic neurotransmitter for all of the ANS?

A

Acetylcholine

106
Q

What does noradrenaline activate in target cell membranes to produce a cellular response?

A

G protein coupled adrenoceptors

107
Q

What does acetylcholine activate in target cell membranes to produce a cellular response?

A

G protein coupled muscarinic acetylcholine receptors

108
Q

What do ligand gated ion channels consist of?

A

Separate glycoprotein subunits that form a central, ion conducting channel

109
Q

What do ligand gated ion channels allow?

A

rapid changes in the permeability of the membrane to certain ions and rapid changes in membrane potential

110
Q

What are the 3 separate proteins of GPCRs?

A

Receptor, G protein, effector

111
Q

What occurs after G protein coupling?

A

receptor activation and effector modulation

112
Q

Describe the structure of the receptor protein

A

Integral membrane protein. A single polypeptide chain with extracellular NH2 and intracellular COOH. There are 7 transmembrane spans with 3 extra and 3 intracellular connecting loops

113
Q

Describe the structure of the G protein

A

Peripheral membrane protein. 3 polypeptide subunits (alpha, beta, gamma)

114
Q

What does the alpha subunit of a G protein contain?

A

Guanine nucleotide binding site that can hold GTP or GDP

115
Q

What happens to the receptor, G protein and effector when there is no signalling?

A

Receptor unoccupied, G protein alpha subunit binds GDP, effector not modulated

116
Q

When a signal is on, what happens once the G protein has coupled the receptor?

A

GDP dissociates and GTP binds to the alpha subunit, G protein dissociates to alpha and beta-gamma subunits,

117
Q

What subunit combines with and modulates the activity of the effector when a signal is on?

A

Alpha

118
Q

If an agonist dissociates from a receptor, what can happen?

A

Signalling can persist

119
Q

What does the alpha subunit act as when the signal is off?

A

GTPase to hydrolyse GTP to GDP + Pi to turn signal off

120
Q

What happens to the alpha subunit when the signal is off?

A

It binds with the beta-gamma subunit again

121
Q

What are receptors which contain 5 glycoprotein subunits that form a central cation conducting channel?

A

Nicotinic acetylcholine receptors

122
Q

What is cholinergic transmission activated by?

A

Synthesis of acetylcholine by choline acetyl transferase

123
Q

What is cholinergic transmission terminated by?

A

Degradation of acetylcholine into choline via acetylcholinesterase

124
Q

What do M1 muscarinic ACh receptors do and how?

A

Increase acid secretion through stimulation of phosphoesterase C

125
Q

What do M2 muscarinic ACh receptors do and how?

A

Decrease heart rate through inhibition of adenyl cyclases and opening of K+ channels

126
Q

What do M3 muscarinic ACh receptors do and how?

A

Increase secretion from the mouth and contract bronchiolar smooth muscle through stimulation of phosphoesterase C

127
Q

What do beta1 adrenoceptors do and how?

A

Increase heart rate and force through stimulation of adenyl cyclase

128
Q

What do beta2 adrenoceptors do and how?

A

Relaxation of bronchial/vascular smooth muscle via stimulation of adenyl cyclase

129
Q

What do alpha1 adrenoceptors do and how?

A

Contraction of vascular smooth muscle through stimulation of phosphoesterase C

130
Q

What do alpha2 adrenoceptors do and how?

A

Inhibition of noradrenaline release through inhibition of adenyl cyclase

131
Q

What is prazosin?

A

Selective, competitive antagonist of alpha1 which acts as an anti-hypertensive

132
Q

What is atenolol?

A

Selective, competitive antagonist of beta1 which acts as an anti-hypertensive and anti-anginal

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