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Therapeutics > general principles of pharamacology lec 1 > Flashcards

general principles of pharamacology lec 1 Flashcards

1
Q

what are diagnostic drugs used for

A

to interpret particular clinical measures

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2
Q

what are the 2 types of pharmaceutical agents used by optometrists

A
  • topical

- systemic

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3
Q

name the 2 different pharmacological principles

A
  • pharmacodynamics

- pharmacokinetics

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4
Q

what does the pharmacodynamics of a drug describe

A

what a drug does to the body

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5
Q

what are the 3 main principles/stages of pharmacodynamics

A
  • drug: receptor interaction
  • biochemical and physiological effects
  • relationship between the drug and therapeutic response

e.g. what the drug binds to, then what the result of that binding is and the relationship of that drug and therapeutic response is.

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6
Q

what does the pharmacokinetics of a drug describe

A

what the body does to the drug

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7
Q

what are the 4 main principles/stages of pharmacokinetics

A
  • absorption e.g. as tablets, oral, injection, inhaled or topical
  • distribution e.g. within the vascular system if its a systemic drug
  • biotransformation e.g. how the body reacts to drugs via biochemical reactions/transformations i.e. how the drug is metabolized and modified chemically
  • excretion e.g. to get rid of the drug
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8
Q

what is an agonist

A

something that mimics the naturally occurring chemical and binds to that receptor

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9
Q

what is an antagonist

A

something that blocks the agonist

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10
Q

how do drugs alter the physiological function of cells

A

exerting their effects by binding to specific target protein molecules

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11
Q

list the 4 specific target protein molecules that drugs bind to in order to alter the function of cells

A
  • classic receptors
  • enzymes
  • transmembrane transport proteins
  • ion channels
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12
Q

give 3 examples of classic receptors that drugs bind to

A
  • beta adrenergic
  • alpha adrenergic
  • histamine
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13
Q

give 2 examples of ion channels that drugs bind to

A
  • sodium channels

- calcium channels

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14
Q

give 2 examples of enzymes that dugs bind to

A
  • carbonic anhydrase

- cyclooxygenase

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15
Q

give 2 examples of transporters that drugs bind to

A
  • Na+ K+ ATPase

- Na+ K+ Cl- co-transporter

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16
Q

name and explain 3 sources of drug

A
  • natural e.g. alkaloids which are extracted from plants, such as atropine
  • semi-synthetic e.g. prepared by chemical modification of natural drugs, such as cyclopentolate
  • synthetic e.g. prepared by chemical synthesis in pharmaceutical laboratories
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17
Q

what is an agonist drug

A

a drug that stimulates receptors

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18
Q

what is an antagonist drug

A

a drug that binds to receptors without stimulating them or preventing binding of the natural agonist

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19
Q

name the two forms of antagonists

A

competitive or non-competitive

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20
Q

how does a non-competitive antagonist work

A

the drug sits on the active site and inhibits the receptor

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21
Q

what is the ideal theory about drug specificity and what is the drawback to this theory

A

ideally a drug should show a high degree of specificity in terms of its binding site, however specify is rarely absolute as increasing the dose of the drug can cause it to affect targets other than the principal one (bind to other things from an overdose), which can lead to side effects

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22
Q

the lower the potency of the drug, the….

A

higher the dose needed and the greater likelihood of unwanted side effects

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23
Q

what does the ‘dose response curve’ represent

A

a characteristic relationship between the dose of the drug and its pharmacological effect

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24
Q

what type of effect does a low concentration drug have as shown in the ‘dose response curve’

A

a no effect range = an initial latency period where the concentration of the drug is too low to have any therapeutic response

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25
Q

what type of effect does an increasing dose of a drug have as shown in the ‘dose response curve’

A

a range of increasing effect = the therapeutic response increases rapidly as the concentration of the drug increases

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26
Q

what type of effect does an even more increasing drug dose have as shown in the ‘dose response curve’

A

a maximum effect range = when all the receptor sites are occupied

(the curve is flat as there is no more effect of the drug on the body)

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27
Q

what are the 2 other words for drug toxicity

A
  • adverse drug reaction - ADR
    or
  • adverse drug event - ADE
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28
Q

what is drug toxicity defined as

A

manifestations of the adverse effects of drugs administered therapeutically or in the course of diagnostic techniques

e.g. during pregnancy, the affect of a drug on the mother could impact the foetus

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29
Q

what is the ratio between the toxic dose and the therapeutic dose of a drug used for

A

it us used as a measure of the relative safety of the drug for a particular treatment

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30
Q

if the toxic dose of a drug is 1000mg, then what should the therapeutic dose of the drug be, to consider it a safe drug

A

he therapeutic dose should have a large difference to the toxic dose, so ideally i should be e.g. 1mg

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31
Q

when do you need to take caution when taking a drug

A

if the toxic dose and therapeutic dose is similar

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32
Q

what may inter-individual responses arise due to

A

pharmacokinetic and pharmacodynamic variation

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33
Q

as well as pharmacokinetic and pharmacodynamic variation, what also appears to be a significant source of variability observed in the response to drugs

A

genetic heterogeneity (pharmacogenetics)

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34
Q

give an example of a drug where different individuals respond differently

A

tropicamide - dark and light irides respond differently = inter-individual variability or differ from genetics

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35
Q

what 4 things is pharmacokinetics the study of with a drug

A
  • absorption
  • distribution
  • metabolism
  • excretion
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36
Q

what is understanding the drugs pharmacokinetics important for

A

when choosing an appropriate route of administration (to see how the body will handle that particular drug)

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37
Q

what can pharmacokinetic factors of a drug cause

A

inter-individual variability on therapeutic response

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38
Q

what is the most preferred route for a drug to be administered in most cases

A

oral route - enteral

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39
Q

other than oral route, what 2 other alternative routes can a drug be administered

A
  • parenteral (non-oral) e.g. injection

- local administration e.g. ophthalmic drugs or inhaled drugs to treat asthma

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40
Q

when will a parenteral (non-oral) e.g. injection route of administration be chosen

A

if a drug is poorly absorbed from the gut or causes gastrointestinal irritation

is an alternative route to oral (enteral)

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41
Q

where do all drugs end up within the body in order to interact with their target

A

in the blood plasma and into the blood stream

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42
Q

why can drugs be excreted within breast milk

A

because there is a small barrier between breast milk and the plasma

43
Q

which form of drug readily penetrate cell membranes

A

non-polar unionised forms of drug as they go across lipid membranes easily

44
Q

what can most drugs which are weak acids or weak bases exist in

A

ionised or unionised forms

45
Q

what is the ratio between ionised and unionised forms of drug determined by

A

the surrounding pH and the dissociation contact (pK), of the drug which represents the pH at which the drug is 50% ionised

46
Q

which form of drug doesn’t cross the lipid membrane easily

A

ionised drugs

47
Q

what does the degree of ionisation determine

A

how the drug crosses the plasma membrane

48
Q

for a weak acid, what equation is the ionisation reaction represented by

A

Ka

HA > A- + H+

49
Q

what equation is the degree of ionisation of a weak acid calculated from

A

the Henderson-Hasselbalch equation:

pH = pKa + log [A-]
[HA]

pKa = association constant (this determines the position of that equation) 
A- = ionised form of acid 
HA = unionised form of acid
50
Q

in an ACID environment (where the pH is low), where will this equation:

     Ka  HA   >   A- + H+
A

the left = the unionised form

the (unionised) drug will get absorbed more readily in the plasma membrane and the acid will be absorbed a lot in the stomach where the pH is low

51
Q

in an ALKALINE environment (where the pH is high), where will this equation:

    Ka HA   >   A- + H+
A

the right = the ionised form

the (ionised) drug won’t get absorbed through the intestine

52
Q

what form will a weak acid in an acid solution mainly be in

A

its unionised form

53
Q

what form will a weak acid in an alkaline solution mainly be in?
and what will this result in?

A

the weak acid will be trapped in its ionised form

the result is that an acidic drug will be concentrated in a compartment with a high pH e.g. an alkaline environment

54
Q

for a weak base, what equation is the ionisation REACTION represented by

A

Kb

BH+ > B + H+

55
Q

what equation is the DEGREE of ionisation of a weak base represented by

A

pH= pKb + log [B]

[BH+]

56
Q

in an ACID environment (where the pH is low), where will this equation:

    Kb BH+  >   B + H+
A

the left = the ionised form

the (ionised) drug WON’T be absorbed across the stomach

57
Q

in an ALKALINE environment (where the pH is high), where will this equation:

    Kb BH+  >   B + H+
A

the right = the un-ionised form

the (un-ionised) drug WILL be absorbed across the stomach

58
Q

what form will a basic drug in an alkaline solution be in and what will this mean for the drug

A

the drug will be in its non-ionised form

it will have greater ability to cross lipid membranes

59
Q

what form will a basic drug in an acid environment be in and what will this mean for an alkaline drug

A

the drug will be trapped as it is ionised

the result is that an alkaline drug will be concentrated in a compartment with a low pH

60
Q

give an example of a drug along with its pKa value, which is most likely to be absorbed from the STOMACH

A

a weak acid such as Aspirin

pKa = 3.5

61
Q

give an example of a drug along with its pKa value, which is most likely to be absorbed from the SMALL INTESTINE

A

a weak base such as Pethidine (like morphine)

pKa = 8.6

62
Q

what 2 things is drug absorption in the intestine determined by

A

ionisation
and
lipid solubility

63
Q

what two types of drugs are poorly absorbed by the intestine and why

A

strong bases pK >10
and
strong acids pK

64
Q

how much % of an orally administered drug is typically absorbed and within how many hours

A

75% in 1-3 hours

65
Q

name 5 factors which affect drug absorption

A
  • gut motility
  • splanchnic blood flow
  • physiochemical factors
  • a drug taken after a meal
  • drugs specifically formulated to delay absorption e.g. capsules, tablets with resistant coatings
66
Q

what affect does a drug taken after a meal have on absorption

A

it is more slowly absorbed since progress to the small intestine is delayed
(done if want to increase absorption time)

67
Q

how does the drug tetracyclines prevent their absorption

A

by binding strongly to calcium and calcium rich foods (especially milk or antacids)

68
Q

what is tetracyclines contraindicated in and why

A

pregnancy and lactation since they both affect tooth and bone formation

69
Q

what other drugs to tetracyclines reduce the absorption of

A

as with other antibiotics, tetracyclines reduce the formation of oral contraceptives

(so px is advised to use alternative forms of contraception during treatment)

70
Q

when the drug is absorbed, at what two times can it either be metabolised

A
  • either before it gets to the blood stream
    or
  • either in the liver

it then goes to the wider circulation

71
Q

what does the term bioavailability refer to

and what is bioavailability dependent on

A

the fraction of the dose that proceeds unaltered from the site of administration and becomes available at the site of action
this is dependent on the rate of absorption

72
Q

what is bioavailability dependent on

A

the rate of absorption

73
Q

in the case of orally administered drugs, other than rate of absorption, what other factors affect the bioavailability

A

first pass metabolism

74
Q

what does first pass metabolism represent

A

the breakdown of a drug by biotransformation by enzymes within the gut wall or liver before it reaches the plasma compartment

(even before the drug has got into the blood stream, it has already undergone biotransformation)

75
Q

what does first pass metabolism explain about the drug glyceryl trinitrate (GTN) used for angina

A

that it is effective sublingually, but not when swallowed

if GTN is given orally, it will not work because glyceryl will be deactivated during first pass metabolism

76
Q

what may first pass metabolism show between individuals

A

inter-individual variation

77
Q

what next thing happens with the drug following absorption

A

distribution

78
Q

list 5 things may cause the distribution of a drug to not be uniform

A
  • physiochemical properties of the drug
  • differences in blood flow between tissues
  • degree of leakiness of the blood vessels in a particular tissue (e.g. bv’s in retina are very tight and don’t leak much)
  • a drug may have an affinity for a particular tissue component e.g. melanin or fat
  • plasma protein binding
79
Q

in what 2 forms can drugs travel in the plasma

A
  • partly in solution (unbound drug)
    or
  • bound to plasma proteins (bound drug)
80
Q

name the 2 main types of plasma protein which both bids specific drugs

A
  • albumin

- b-globin and a-acid glycoprotein

81
Q

what types of drug does albumin mainly bind

A

acidic drugs

e.g. warfarin and non-steroidal anti-inflammatory drugs (NSAID)

82
Q

what types of drug does b-globin and a-acid glycoprotein mainly bind

A

basic drugs

e.g. propanolol

83
Q

what does protein binding potentially reduce

A

the availability of the active form of the drug

protein-bound drugs show a restricted tissue distribution and slow elimination i.e. it is a variable that affects the amount of drug that reaches the target

84
Q

in what 2 processes does the elimination of drugs from the body occur by

A
  • metabolism (biotransformation)
    and
  • excretion
85
Q

what does the metabolism of a drug involve

A

the enzymatic conversation of the drug into another chemical entity

86
Q

what does excretion of a drug involve

A

the elimination of the unchanged drug (or its metabolites)

87
Q

where does drug metabolism predominantly occur

A

in the liver

88
Q

what two types of chemical transformation does drug metabolism involve

A

phase I
and
phase II reactions

89
Q

what is the purpose of drug metabolism

A

to make the drug more hydrophilic, to hasten its excretion by the kidneys

90
Q

what do phase I reactions of metabolism involve

A

adding or unmasking a functional group to the uncharged hydrophobic ionised form of the drug to make it charged e.g. -OH, -NH2, -SH. oxidations are the most common reactions and are usually carried out by a family of microsomal enzymes (in the liver) known as cytochrome P450 (CYP)

in other words…
the drug is made more hydrophilic by unmasking the iconic groups within the molecule by introducing a +ve or -ve charge, this is done by oxidation which makes the molecule more +ve or -ve charged or done by adding functional groups

91
Q

what is another term for phase II processes of metabolism

A

conjugation

92
Q

what do phase II processes of metabolism involve

A

the attachment of a substituent group e.g. glucuronyl, acetyl, methyl or sulphate. these reactions make the drug more polar (adds more charge) making it more hydrophilic so that it can be excreted by the kidneys

93
Q

how are most drugs excreted from the body

and in what two forms can they be

A

in the urine

either unchanged or as polar metabolites

94
Q

other than in the urine, how are other drugs excreted

A

they are first secreted into bile via the liver, followed by loss of the drug via the faeces

95
Q

how is the rate of renal clearance variable

A

some drugs are lost in an single transit whilst others are cleared more slowly

96
Q

which type of drug action can only be terminated by renal elimination and what implications does this have

A

the drugs that are excreted without biotransformation

therefore these types of drugs (which are secreted via the kidney) need to be prescribed with special care in the elderly and in those with altered renal function

97
Q

list 4 types of variables affecting drug metabolism

A
  • some drugs increase the activity of drug metabolising enzymes e.g. barbiturates
  • other drugs inhibit drug metabolising enzymes e.g. erythromycin, ethanol (drugs that interact with other drugs)
  • genetic polymorphisms lead to inter-individual variation in drug metabolism
  • age
98
Q

explain how neonates are a variable that affects drug metabolism

A

neonates may have an immature drug metabolising mechanism

99
Q

explain how the elderly are a variable that affects drug metabolism

A

the elderly may have impaired hepatic metabolism of drugs and also show impaired glomerular filtration rate reducing renal clearance

100
Q

list 4 types of topical drugs used by all optometrists

A
  • diagnostic drugs e.g. mydriatics, cycloplegics, topical anaesthetics
  • lubricants e.g. hypromellose, sodium hyaluronate
  • anti-infectives e.g. fusidic acid, chloramphenicol
  • anti-allergy e.g. anti histamine, mast cell stabilisers
101
Q

list 2 types of topical drugs used by specialist therapeutic prescribers

A
  • corticosteroids

- anti-glaucoma

102
Q

list 2 types of systemic drugs used by all optometrists

A
  • antihistamines e.g. cetirizine, loratadine
  • NSAIDs e.g. ibuprofen, aspirin
  • eye-nutrients e.g. anti-oxidant vitamins/essential fatty acids
103
Q

list 2 types of systemic drugs used by specialist therapeutic prescribers

A
  • oral antibiotics e.g. tetracyclines

- carbonic anhydrase inhibitors e.g. acetazolamide

Therapeutics (19 decks)

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