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Pharmacology > Pharmacokinetics 1 and absorption > Flashcards

Pharmacokinetics 1 and absorption Flashcards

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1
Q

what are the 4 stages pharmacokinetics?

A
  • Absorption from the site of administration
  • Distribution within the body
  • Metabolism (breakdown and/or conjugation)
  • Excretion
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2
Q

Pharmacodynamics

A

what a drug does to the body

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3
Q

pharmacokinetics

A

what happens to the drug in the body

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4
Q

Pharmacodynamics specificity

A

Specific to drug or drug class

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5
Q

pharmacokinetics specificity

A

Non-specific, general processes

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6
Q

Pharmacodynamics specificity relies on

A

-Interaction with cellular components
-Effects at the site of action
Concentration-effect relationship
-Modification of disease progression
-Unwanted effects
-Drug interaction
-Inter- and intra-individual differences

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7
Q

pharmacokinetics in the body relies on

A
  • Absorption from the site of administration
  • Delivery to site of action
  • Elimination from the body
  • Time to onset of effect
  • Duration of effects
  • Drug interaction
  • Inter- and intra-individual differences
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8
Q

ethanol metabolism

A

draw it out

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9
Q

why is pharmacokinetics important?

A

Critical to new medicines research and development

Understanding pharmacokinetics is important to prescribing safely

Understanding what can go wrong with drug dosing and drug-interactions

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10
Q

what are Fentanyl Transdermal Patches?

A

opious drug which is 100 times more potent than morphine

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11
Q

what enzyme metabolises Fentanyl?

A

cytochrome P450 3A4 isozyme

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12
Q

what affects release and how much is released and onset?

A

12-18 hour onset to reach peak pain relief (slow onset so people think they need more)

temp affects release

40% still in the patch after 72hours

levels fall to 50% after removing the patch 17 hours prior

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13
Q

what are the major routes of administration of drugs into the body?

A 
Sub lingual 
IV
Oral 
Sub cutaneous
Up the bum – suppository – rectal
Inhalation
Nasal 
Intramuscular 
Intravitreal (in the eye) 
Trans dermal – patch on the skin
Pessary 
spinal canal - into csf
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14
Q

why is intramuscular quicker to get into the blood stream that intradermally?

A

there are larger and more blood vessels in the blood

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15
Q

Oral administration - Advantages

A
  • Easy
  • Slow release
  • drugs can be formulated to protect against digestive enzymes and acid
  • cheap and safe
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16
Q

Oral administration - Disadvantages

A
  • unsuitable for patients strictly mil by mouth
  • mostly absorbed slowly
  • unpredictable absorption
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17
Q

Rectal administration - Advantages

A

good absorption, avoids the first pass metabolism - haemorrhoids vein drains directly into the inferior vena cava

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18
Q

Inhalation administration - Advantages

A

large SA, bronchodilators steroids targeted to lungs with low levels of absorption

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19
Q

Inhalation administration - Disadvantages

A

bioavailability depends on the patients inhaler technique and the size of the particles generated

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20
Q

Where are most drugs that are taken orally absorbed?

A

in the small intestine - large SA

some absorption can take place in the stomach

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21
Q

which factors affect absorption?

A 
ionisation of a drug
molecular size
gut content (fasted/fed)
GI motility
particle size and formulation
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22
Q

at what molecular weight does passive absorption become worse/

A

> 500nm

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23
Q

how long does it take 75% of drugs to be absorbed after being taken orally?

A

1-3 hours

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24
Q

how are drugs that are taken orally absorbed?

A

Passive difusion, carria media transporters, pinocytosis/endocytosis

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25
all drugs have to bass at least one cell barrier in order to get into the effector tissue - one method excluded - which is this?
Intra venous
26
which kind of cell linings are often present barriers to drugs moving from one ‘compartment’ to another
epithelial and endothelial
27
which barriers are the most difficult to permeate/
BBB and placental
28
what do aqueous pores do
allow transport of materials
29
where would you mind fenestrated capillaries
GI tract, renal glomeruli, endocrine glands, choroid plexus
30
which organs would you fined pores in the capilaries
liver, spleen and bone marrow drugs freely pass and so detox and excrete
31
where would you find tight junctions in capillaries?
BBB, muscle and heart
32
what ways can drugs cross membranes?
Passive diffusion, though aq pore, and carrier protein (requires ATP), pinocytosis take up into vesicle (requires ATP)
33
what will diffuse across across a lipid membrane?
only unionised (non charged form of the drug)
34
what do drugs ionise according to?
their pKa
35
Weak acids will be ionised at
higher pH
36
Weak bases will be ionised at
lower pH
37
The pKa is the pH at which ionised and non-ionised forms are..
equilibrium
38
Alkali drugs
high pKA – ionised in acidic condions
39
why does aspirin get trapped in the urine?
has a low pKa due to being a weak acid- the urine has a high pKa
40
why is neurotoxin safe to eat in meat?
neurotoxin is basic - so has a high pKa the gut has a low pKa so safe to eat
41
alkalising urine can be used to treat overdoses of what drugs
weak acids
42
where are strong bases ionised?
in the intestines | - poor absorption
43
with a weak acidic drug such as aspirin where will it be most ionised? pH?
in alkaline pH - such as in the urine
44
what is the pKa of aspirin?
3.5
45
pethidine is a weak base drug with a pKa of 8.6, where will ionisation the base be greatest?
low pH, such as in the stomach
46
carriers in cell membranes mediate the transport of what?
sugars, amino acids, neurotransmitters and metal ions
47
what do solute carrier transporters (SCLs) do?
passively transport substrates down its concentration gradient
48
active transport -
transferring against the concentration gradient - requires ATP
49
how many genes are thought to code for transporters
300
50
to traverse cellular barriers (Mucose, BB, placenta) drugs must cross
lipid membranes
51
drugs cross lipid membranes by
passive diffusion transfer or carrier - mediated transfer
52
what is the main factor that determines rate of diffusional transfer across membranes?
drugs lipid solubility
53
what is a less important factor in determining rate of diffusional transfer?
molecular weight
54
henderson- hasselbalch equation states
ionisation of weak acids and weak bases varies with pH
55
with weak acids and weak bases only....... can diffuse across lipid membranes - pH partition
uncharged species - protonated form of weak acid - unprotonated form of weak base
56
what does pH partition mean?
that weak acids tend to accumulate in compartments of relatively high pH (weak bases do the reverse)
57
carried mediated transport in the renal tube,BB and GI epithelium is important for some drugs that are
chemically related to endogenous species
58
Bioavailability (F)
extend and rate at which the active moiety of the drug or metabolite enters the circulation, thereby accessing the site of action.
59
what bioavailability does IV immediately give?
100%
60
how would you work out bioavailability?
blood plasma conc. curve Area under the curve oral route / area under the curve IV = absolute bioavailability
61
insulin bioavailability
0% - broken down by enzymes
62
what is the first pass effect?
where when a drug is taken - absorbed into the GI tract - passes through the portal vein into the liver - the liver breaks down and greatly reduces the bioavailability of the drug
63
which would have a longer half life? IV or oral?
Oral | oral would take longer to onset, have a more blunter peak plasma concentration and longer duration of action
64
what affect does slower absorption of drug have on peak conc.
lower peak
65
Intra venous administration allows
rapid onset and full absorption of drug
66
what is an IV loading dose called?
bolus
67
what 2 methods of IV are combined to maintain blood concentration?
iv bolus (loading dose) and then Iv infusion
68
IV infusion avoids
first pass
69
sublingual absorption
under the tongue - mucous membrane with lots of capillaries, straight into the blood so avoids first pass
70
would rectal or oral have higher bioavailability?
rectal
71
Nasal sprays
nasal cavity is well vascularised, quick into circulation, small molecules with a local effect
72
intravitreal uses
-used for diabetes retanopothy
73
(eye drops)
saline based | - antihistamines or antibiotics
74
what is intrathecal
straight into the spinal canal - into the CSF - crosses the BBB
75
what are prodrugs?
drugs which are administered but the need to be metabolised by the body to become the active form
76
example of prodrug?
codine - created into morphine | AZT - doesn't have direct effect on HIZ, effects reverse transcriptase
77
which enzyme converts coding to morphine
CYP2D6
78
the specialist formulation of the contraceptive implant - how does it work?
releases hormones slowly, made of copper which also has a natural effect on our hormone levels
79
how are antibody-drug conjugates used?
mainly used against cancer, drug which has a selective antibody and a cytotoxic agent - antibody sticks to marker on cancer cell and binding causes the reaction to kill the cells
80
which form of dosing is most common?
oral
81
most absorption of oral is in
the small intestine
82
bioavailibilty requires
absorption and surviving early metabolism (GI wall and first pass)

Pharmacology (18 decks)

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