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1st Year - Principles > Pharmacology 1, 2 and 3 - Intro to drug action, drug movement in the body, elimination > Flashcards

Pharmacology 1, 2 and 3 - Intro to drug action, drug movement in the body, elimination Flashcards

1
Q

What are the 2 compromises of pharmacology and what do they mean?

A

Pharmacodynamics - what a drug does to the body (biological effects and mechanisms of action)Pharmacokinetics - what the body does to a drug (absorption, distribution, metabolism and excretion)

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2
Q

What selectively of drugs result from?

A

chemical structure of drugTarget recognising only ligands of a precise type

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3
Q

Examples of targets of drugs? (5)

A

enzymes, carrier molecule, ion channels, receptors, RNA/DNA

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4
Q

What are receptors?

A

Macromolecules that mediate the biological actions of hormones and neurotransmitters

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5
Q

2 types of drugs acting on receptors and meaning?

A

Agonists - a drug that binds to a receptor and produces a cell responseAntagonists - a drug that blocks the actions of agonists

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6
Q

What is a ligand?

A

A molecule that binds to a receptor

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7
Q

Out of affinity and efficacy, what does an agonist and antagonist posses?

A

Agonist = affinity and efficacyAntagonist = affinity

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8
Q

How does an agonist work?

A

A conformational change occurs due to the presence of an agonist molecule making it act and therefore producing a biological response

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9
Q

Affinity?

A

Strength of association between ligands and receptor

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10
Q

Dissociation rate compared to affinity

A

Low affinity = high dissociation rate

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11
Q

What are the 2 things that determine affinity

A

Closer the fitNumber of bonds

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12
Q

Efficacy?

A

Ability of agonist to provoke a cellular response

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13
Q

Low efficacy?

A

Low ability to produce a cellular response

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14
Q

Relationship between receptor occupancy and agonist concentration?

A

As agonist conc. increases, receptor occupancy also increases

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15
Q

EC50?

A

Concentration of agonist which elicits a half maximal response

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16
Q

Concentration (or dose) response relationship - linear plot - relationship shape

A

Hyperbolic

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17
Q

Why is it easier to plot the concentration response relationship as the log of the agonist concentration?

A

It allows you to present data over a wider range of concentrations It is easier to see the max70% of the curve is a straight line

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18
Q

What shape is the response when the concentration response relationship is plotted as a semi-logarithmic plot?

A

Sigmoidal

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19
Q

What can a highly potent drug do?

A

Evoke a larger response at lower concentrations

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20
Q

What are partial agonists

A

Drugs that bind to receptors but only have partial efficacy meaning they cannot evoke the same response as a full agonist

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21
Q

Competitive antagonism?

A

Binding of agonist and antagonist occur at same (orthosteric) site

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22
Q

Non-competitive antagonism

A

Agonist binds to orthosteric site and antagonist binds to allosteric site (activation cannot occur if antagonist is bound)

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23
Q

Drug disposition?

A

The fate of drugs in the body

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24
Q

Determinants of drug disposition

A

AdsorptionDistributionMetabolismExcretion

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25
Q

Adsorption?

A

The process by which a drug enters the body from its site of administration

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26
Q

Distribution

A

The process by which the drug leaves the circulation and enters the tissues perfused by the blood (once inside the tissue, further blood-independant distribution may occur)

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27
Q

Metabolism

A

The process by which tissue enzymes (particularly in the liver-hepatic metabolism) catalyse the chemical conversion of a drug to a more polar form that is more readily excreted by the body

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28
Q

Excretion

A

The process that removes the drug from the body (principally the kidneys - renal exertion)

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29
Q

Aside from the liver, where does metabolism also occur?

A

GI tract and lungs

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30
Q

Aside from the kidneys, where does excretion also occur?

A

Breath, sweat and milk

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31
Q

What is elimination (sum)?

A

metabolism + excretion

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32
Q

Where does most absorption occur?

A

in the Small intestines (due to large SA)

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33
Q

Where is ethanol absorbed

A

The stomach

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34
Q

name for when unchanged drugs leave the body via the faeces?

A

Egestion

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35
Q

3 physiochemical factors controlling drug absorption

A

Solubility (drug must be dissolved to be absorbed)Chemical stability (some drugs are destroyed by the stomach acid or enzymes in the GI tract)Lipid to water partition coefficient (rate of diffusion increases with lipid solubility of drug)

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36
Q

What does ampithatic mean?

A

Has both polar and non polar parts (drugs must be ampithatic)

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37
Q

In terms of weak/ strong acids/bases, what are many drugs

A

Weak acids and bases existing in both the ionised and unionised forms

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38
Q

pH=

A

pH=-log10[H+]

39
Q

Out of ionised and unionised forms, what readily diffuses across the lipid bilayer

A

Unionised forms

40
Q

What does the degree of ionisation of a drug depend on?

A

pKa of drug and local pH

41
Q

pKa?

A

pH @ which 50% drug is ionised and 50% is unionised

42
Q

What equation can be used to determine the proportion of ionised drug?

A

Henderson-Hassleback

43
Q

Henderson hassleback equations for acid and base

A

Acid: pKa - pH = log(HA/A-)Base: pKa - pH = log (BH+/B)

44
Q

As pH increases, are acid drugs increasingly or decreasingly ionised?

A

Increasingly

45
Q

What is sometimes absorbed in the stomach acid?

A

Weak acids

46
Q

Where does most absorption occur?

A

Small intestines (even weak acids)

47
Q

Are weak acids and weak bases or strong acids and strong bases better absorbed?

A

Weak acids and weak bases

48
Q

Factors affecting GI absorption? (6)

A

GI motility (rate of stomach emptying and movement through intestine) - modified by drugs and foodpH @ absorption siteBlood flow to GI tract (increased by food)Way in which tablet, capsule, etc. is manufactured (can be customised to release drugs at different rates/ sites)Physiochemical interactions (e.g. rate of absorption is modified by calcium rich food)Presence of transporters in membrane of epithelial cells of GI tract

49
Q

Oral Availability? Equation?

A

Fraction of drug that reaches the systemic circulation after oral ingestion amount in systemic circulation/ amount administered

50
Q

Systemic availability? Equation?

A

Fraction of drug that reaches the systemic circulation after absorptionamount in systemic circulation/ amount absorbed

51
Q

First pass/ pre-systemic metabolism?

A

Drugs administered orally, once absorbed can be inactivated by enzymes in the gut wall and liver

52
Q

2 categories of routes of drug administration?

A

ENTERAL-via GI tractParenteral - any route not via the GI tract

53
Q

4 enteral routes of drug administration?

A

OralSublingual BuccalRectal

54
Q

4 parenteral routes of drug administration?

A

IVintramuscularsubcutaneousInhalationTopical

55
Q

What kind of drugs are able to move freely between the compartments of the body?

A

Free drugs

56
Q

Volume of distribution?

A

Apparent volume in which a drug is dissolved

57
Q

Vd=

A

Dose/ plasma concentraiton (for a drug administered IV)

58
Q

Vd

A

Implies that the drug is retained in the vascular compartment

59
Q

Vd

A

Implies that the drug is restricted to extracellular fluid

60
Q

Vd>15L

A

Indicates distribution throughout total body water (or concentration in certain tissue)

61
Q

What is the drug concentration that must be achieved to achieve an effect

A

Minimum effective concentration

62
Q

What is the concentration level that causes significant adverse affects

A

Maximum tolerated concentration

63
Q

What is the phase between MEC and MTC

A

therapeutic window

64
Q

Therapeutic window of safe drugs

A

Large

65
Q

Therapeutic ratio =?

A

MTC/MEC

66
Q

Kabs?Kel?

A

Absorption rateElimination rate

67
Q

If given IV, what is the initial concentration of drug equation?

A

Co = D/ Vd (C=m/V)

68
Q

What factor does concentration of drug at a later time depend on (Ct)

A

Kel

69
Q

What type of kinetics do most drugs exhibit

A

First order

70
Q

Ct=

A

Ct= Coe^-Kel-t

71
Q

Half life

A

Time taken for Ct to fall by 50%

72
Q

What is t1/2 inversely related toEquation

A

Kelt1/2 = 0.69/ Kel

73
Q

What is Cp shorthand for

A

Plasma concentration

74
Q

Are Kel and half life dependant on the dose administered

A

No

75
Q

What is clearance (Cl)

A

The volume of plasma cleared of drug per unit time (a constant relating the rate of elimination to plasma concentration)

76
Q

What type of kinetics does clearance apply to?

A

First order

77
Q

Rate of elimination =

A

Rate of elimination = Cl X Cp

78
Q

Maintenance dose rate?

A

Dose per unit time required to maintain a given plasma concentration

79
Q

At steady state (SS)

A

Rate of elimination

80
Q

Cps.s.=

A

Cps.s. = maintenance dose rate / Cl

81
Q

For drugs that exhibit first order kinetics, what is the steady state (SS) plasma concentration linearly related to

A

infusion rate

82
Q

What is the time to reach Css determined by?

A

half life (NOT the infusion rate)

83
Q

When is Css reached?

A

After approx. 5 half lives

84
Q

What is bioavailability (F)

A

Fraction of drug administered that enters the systemic circulation?

85
Q

Css(average) = (oral dose)

A

FXdose / Clp X dosage interval

86
Q

Volume of distribution (Vd)

A

Volume into which a drug appears to be distributed with a concentration equal to that of plasma (relates plasma concentration (Cp) to the amount of drug in the body (Ab)

87
Q

Ab = ?

A

Ab = Vd X Cp (C=mXV)

88
Q

Loading dose (LD)?

A

An initial high dose of a drug given at the beginning of a course of treatment before stepping down to a lower maintenance dose

89
Q

LD (for IV) =

A

LD (IV) = Vd X target Cp

90
Q

LD (for oral) =

A

LD = Vd X target Cp / F

91
Q

In terms of Vd and Cl, what does t1/2 =?

A

t1/2 = 0.693 X Vd / Cl

92
Q

What happens during zero order kinetics?Example of 2 drugs that do this?

A

Drugs are initially eliminated at a constant rate, rather than at a rate proportional to their concentration (straight line on graph rather than curve)Ethanol and phenytoin

93
Q

When do drugs exhibit zero order kinetics?

A

When Cp > km of an enzyme that metabolises it

1st Year - Principles (37 decks)

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