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Y1 IHP > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

What does ADME stand for

A

Absorption
Distribution
Metabolism
Excretion

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2
Q

Drug definition

A

A chemical substance of known structure (non nutritional) which produces a biological effect when administered

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3
Q

How are drugs categorised (Anatomical classification system)

A

Physiological system (target area eg - blood, respiratory system)

Therapeutic group (effect eg - stimulants, contraceptives)

Chemical properties (structure)

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4
Q

Most common/successful drugs

A

Lisoprinal (ACE inhibitor)

Atorvastatin’s (for high cholesterol)

Penicillin (200mil lives saved)

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5
Q

Major drug failure examples

A

Thalidomide (treated morning sickness but caused serious birth defects & maternal death

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6
Q

Relentlessly incurable diseases

A

the Cold, Alzheimer’s, Diabetes I

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7
Q

Common drug administration methods

A

Oral, Rectal, Intravenous, Nasal, Sublingual, intramuscular, inhalation, Transdermal, intrathecal

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8
Q

How are most small molecule drugs delivered, where is absorption & contributing physiological factors

A

Orally - absorbed in SI

Gut content, GI motility

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9
Q

How do drugs move across membranes

A

Simple diffusion (through lipids)

Facilitated diffusion (through aqueous channels)

Carrier protein transport (ATP dependant or independent)

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10
Q

Which conditions aid the movement of drugs

A
  • high conc grad
  • low molecular weight
  • low degree of ionisation
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11
Q

What is the first pass effect

A

a large reduction in concentration of orally taken drugs before reaching systemic circulation (reduces bioavailability)

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12
Q

Where does the first pass effect take place and how

A

The gut or liver - following absorption the drugs maybe travel through the portal vin to the liver where they are metabolised

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13
Q

Bioavailability definition

A

How much of a orally given drug makes into circulation in is active form

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14
Q

IV vs oral administration (bioavailability)

A

IV reaches blood much quicker and at greater concentrations (but is also undergoes a rapid elimination process)

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15
Q

Oral bioavailability equation

AUC = area under curve

A

Oral bioavailability = AUC oral

/ AUC iv

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16
Q

what does Oral bioavailability calculation show (eg for a 50% result)

A

for a 50% result the dose must be doubled when converting from intravenous to oral route

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17
Q

Oral administration pros/cons

A

pros - easy to administer

cons - subject to first pass effect

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18
Q

Rectal administration pros/cons

A

pros - can be used for vomiting patients

cons - bioavailability varies depending on blood supply

19
Q

Inhalation administration pros/cons

A

pros - local effect, very fast

cons - not suitable for large molecules (can leak into systemic blood)

20
Q

Intravenous administration pros/cons

A

pros - 100% bioavailability

cons - enters tissue rich in blood vessels first

21
Q

Intrathecal administration pros/cons

A

pros - cross the blood-brain barrier

cons - difficult to administer

22
Q

Transdermal administration pros/cons

A

pros - not subject to first pass effect

cons - bioavailability depends on the subcutaneous muscle/fat

23
Q

Alcohol absorption (empty stomach)

A
  • Some absorbed in stomach most moves into SI where it is rapidly absorbed
24
Q

Alcohol absorption (after a meal)

A
  • Pyloric sphincter is closed so alcohol is kept in stomach longer where is it slowly absorbed
25
Q

By what % can a fatty meal reduce peak blood alcohol concentration

A

up to 50%

26
Q

Ethanol key propertires

A
  • Small molecule
  • hydrophobic & hydrophilic
  • readily cross membranes & protein channels
  • moves passively down conc grad
27
Q

what does the compartmental model refer to

A

Drugs not being evenly distributed between tissues

28
Q

What is blood distribution dependant upon

A
  • blood flow for delivery speed

- lipid solubility for tissue accumulation

29
Q

Pattern of drugs distribution for Oral & IV administration

A

oral - slow even filling

IV - brain/heart first then redistributed

30
Q

Movement pathway of drugs through membranes (compartment to compartment)

A

GI tract -> GI tissue (fenestrae)

Blood -> Liver (loose barrier - pores)

Blood -> CNS/heart (tight barrier)

31
Q

Lipid solubility relation with drugs

effects measuring of drug in blood

A

poorly lipid soluble = more drug in blood

highly lipid soluble = more drug in lipid

32
Q

Alcohol distribution key facts

A
  • restricted to total body water
  • doesn’t enter adipose tissue
  • can cross the blood/brain barrier leading to cognitive & motor impairment (500mg/100ml = lethal)
33
Q

Why does alcohol effect different genders differently

A

males have higher body water content (68% compared to 55%)

Meaning females will have a high BAC when drinking the same amount as males

34
Q

Phase I metabolism of drugs

A

Drug goes in primary product comes out

expose or add functional group (oxidation, reduction, hydrolysis)

35
Q

Phase II metabolism of drugs

A

Primary drug goes in secondary product comes out

Conjunction (glucuronide, sulphate, methyl, glutathione)

36
Q

What is drug metabolism doing and why

A

making a lipophilic drug more hydrophilic

both primary and secondary products are excreted (better if hydrophilic)

37
Q

How is alcohol metabolised in the liver

A

Ethanal -> acetaldehyde (ADH enzyme) -> acetic acid (oxidised in the mitochondria)

acetic acid is an inert metabolite and is secreted

38
Q

Acetaldehyde is toxic metabolite what does it do

A

causes flushing, ^ HR, headaches, nausea

39
Q

Alcohol elimination follows zero order kinetics why is this? (a constant amount is eliminated over time regardless of concentration)

A

no more Alcohol dehydrogenase (ADH) can be produced so metabolism continues at a steady rate and alcohol will accumulate in the bloodstream

40
Q

What rule does first order elimination kinetics follow

A

The higher the drug concentration the quicker it is eliminated (high gradient of initial curve on a graph)

a constant fraction is eliminated per time eg 50%

41
Q

Renal clearance equation = ?

A

Renal clearance = (Urinary conc x urinary volume) / plasma concentration

42
Q

Total clearance equation = ?

A

Total clearance = CLtotal = CLrenal +CLnonrenal

Total clearance = volume of plasma cleared of drug per untie by metabolism & excretion

43
Q

Non renal clearance pathway examples

A

Metabolism, sweating, expiration

Y1 IHP (4 decks)

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