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Medicine Unit 3 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

what type of drug is flucloxacillin

A

beta-lactam antibiotic

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2
Q

chemistry of flucloxacillin

A

has a fluoride and a chloride
has a core penicillin part
is a beta-lactam antibiotic so has a beta-lactam part in the structure

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3
Q

pharmacology of flucloxacillin

A

targets bacterial transpeptidase enzymes
=penicillin-binding protein (PBP)
activity: irreversible inhibitor
=suicide substrate

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4
Q

physiology of flucloxacillin

A

-D-ala-D-ala is integral part of cell wall peptidoglycan, PG: structure/synthesis
transpeptiases normally crosslink :the D ala to other amino acids in PG
beta lactase inhibition of the cell wall synthesis
dividing bacteria lose rigid cell wall integrity
osmosis and cells then pop
they’re bactericidal

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5
Q

clinical side of flucloxacillin

A

antibiotic
narrow spectrum, gram positive
infections caused by sensitive organisms e.g. staphylococcus and streptococcus

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6
Q

what is pharmacokinetics

A

what the body does to the drug
absorption, distribution, metabolism, excretion/elimination

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7
Q

what is pharmacodynamics

A

what the drug does to the body

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8
Q

absorption

A

from outside to inside
-routes of administration
-bioavailability
-drug properties
-biological properties

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9
Q

distribution

A

form one place to another in the body
-volume of distribution
-blood flow
-drug properties
-biological properties

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10
Q

metabolism

A

from one thing to another
-biotransformation
-transforming enzymes
-drug properties
-biological properties

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11
Q

excretion/elimination

A

from inside to outside
-clearance
-removal mechanisms
-drug properties
-biological properties

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12
Q

routes of administration

A

parenteral
enteral

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13
Q

parenteral definition

A

avoiding the gastro-intestinal tract

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14
Q

methods of parenteral administration

A

intravenous
intramuscular
sub-cutaneous
epidural
trans-dermal
sublingual
inhalation

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15
Q

intravenous

A

directly into the blood

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16
Q

intramuscular

A

directly into a muscle
highly vascular tissue

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17
Q

sub-cutaneous

A

under the skin
poorly vascular space q

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18
Q

epidural

A

into the epidural space

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19
Q

systemic

A

drug will be administered everywhere

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20
Q

topical

A

treatment is localised
e.g. local anaesthetic

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21
Q

trans-dermal

A

across the skin

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22
Q

sublingual

A

under the tongue

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23
Q

inhalation

A

through breathing via the lungs

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24
Q

enteral

A

via the gastro-intestinal tract

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25
examples of enteral
oral rectum
26
oral
into the mouth then stomach then intestines
27
rectum
e.g. suppositories
28
oral bioavailability
is the same as fractional availability fraction of a drug that gets into the systemic circulation 100%= all the drug in the tablet gets into the plasma higher the bioavailability the more useful the drug will be as an oral, systemic medicine
29
what factors affect oral bioavailability
drug stability within the gut drug absorption across the gut wall into the blood drug metabolism in the liver (first pass effect)
30
drug stability in the gut
chemical stability: acidic in the stomach, pH varies in small intestine biological stability: enzyme action in the gut, intestinal bacteria drug properties: chemical (the drug), pharmaceutical (the formulation), biological (the patient)
31
drug absorption across the gut wall
gut is adapted pathway: gut lumen, gut epithelium, extracellular matrix, capillary endothelium, blood vessel lumen
32
what does absorption in the gut depend on
drug properties: solubility size, pKa pharmaceutical gut properties: anatomy, physiology, pathology
33
which drugs cross membranes most easily
unionised
34
weak acid and absorption
H+ + A- reverse HA un-ionised form HA predominates better absorption
35
when does equilibrium shift
at low pH
36
weak base and absorption
H+ + B reverse HB+ ionised form HB+ predominates poor absorption
37
drug metabolism in the liver
drugs with substantial hepatic metabolism may have poor oral bioavailability
38
which is the principle organ of drug metabolism
the liver
39
first pass effect
drugs absorbed in most of the gut pass entirely to the liver hepatic portal vein runs from the gut to the liver
40
how to calculate volume in ml
amount in mg/ concentration in mg.ml-1
41
volume of distribution equation
total amount of drug in the body/ concentration in the plasma defines the relationship between two real important values
42
why concentration in the plasma
something measurable directly related to clinical effects
43
why is it an "apparent" volume of distribution
drug may not leave the blood, erythropoietin= very high Cp drug freely enters/leaves the cells, cimetidine= low Cp drug doesn't enter the cells (evenly in the extracellular fluid)gentamicin= high Cp drug accumulates in fat (lipophilic), midazolam=very low Cp
44
effect of high blood flow
high blood flow to the brain propofol= IV general anaesthetic intravenous= rapid delivery to brain
45
effect of low blood flow
low blood flow to the bones/cartilage/joints antibiotics difficult to achieve adequate concentrations of drug= infections difficult to treat
46
what does the volume of distribution tell us
the distribution of the drug in the body compared to the plasma how much drug is required in the body to achieve a specific concentration in the plasma
47
what does metabolism do to drugs
alters the chemical structure biochemical (enzymes)
48
where are drugs metabolised
liver gut wall kidney lung plasma any tissue with metabolic activity
49
what are the two phases of drug metabolism q
synthetic conjugation
50
synthetic
oxidation: hydroxylation, dealkylation,deamination reduction hydrolysis makes the drug more polar and soluble
51
conjugation
glucuronidation methylation sulphation acetylation glutathione makes drug larger makes the drug more polar
52
what do drugs change into in the synthetic phase
can convert to active, inactive, toxic metabolites
53
what do drugs change into in the conjugation phase
converts drug to inactive form except morphine
54
phase one of phenacetin metabolism
it is a prodrug and is inactive changes to paracetamol which is active
55
phase one paracetamol metabolism
NAPQI toxic and in phase two of this drug metabolism forms glutathione-conjugated paracetamol which is inactive
56
phase two of paracetamol metabolism
forms glucuronide-conjugated paracetamol inactive
57
elimination
disappearance of the drug from the plasma excretion: parent drug is physically gone metabolism: parent drug changed into something else
58
excretion
physical removal of the drug from the body kidney-urine lungs-breath skin-sweat
59
what is renal elimination promoted by
increased polarity increased aqueous solubility increased size metabolites by phase one and two are normally faster eliminated
60
rate of elimination
drug mg is eliminated from the plasma over time in mins units: mg.min-1
61
clearance
plasma ml is cleared of drug over time min units: ml.min-1
62
rate of constant elimination ke
proportion of drug (unitless) eliminated in one unit of time min units: min-1
63
half-life (t1/2)
time in min taken for the plasma concentration to fall by half units: min
64
what is the rate of elimination proportional to
the concentration
65
what is the proportionality constant
clearance
66
how to achieve a desired plasma concentration
dose= Vd x Cp mg= ml x mg.ml-1
67
how to maintain a desired plasma concentration
dose rate = Cl x Cp mg.min-1 = ml.min-1 x mg.ml-1 cl= flow rate of leak
68
how to calculate the half life
t1/2 =ln2 / ke ke= rate constant of elimination
69
if you increase the clearance what happens to the half-life
shortens
70
for an oral drug what is ideal dosing q
once per da
71
short half life q
second/minutes onset/offset rapid uses a lot of drug
72
long half life
hours/days onset/offset slow uses less drug
73
1st order elimination
constant clearance rate of elimination is proportional to the concentration in the plasma linear kinetics practical, predictable and analytically simple

Medicine Unit 3 (28 decks)

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