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phar24 > week 2 > Flashcards

week 2 Flashcards

1
Q

list the four stages of drug disposition

A
  1. Absorption
  2. Distribution (plasma/tissue distribution)
  3. Metabolise (biotransformation)
  4. Excretion = out of body (different to elimination which means not active anymore)
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2
Q

list the three basic movements of substances across a cell membrane

A
  1. passive movement
  • paracellular transport
  • diffusion
  • facilitate diffusion (carrier)
  1. active transport
  • movement against gradient
  • uses carriers & energy
  1. pinocytosis
  • fluid endocytosis
  • also internalise small particles suspended in extracellular fluids
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3
Q

define SLC

A

= solute carriers co-transporter = use gradient not energy to co-transport solutes e.g. inorganic ions, amino acids, lipids. Sugars, neurotransmitters, drugs

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4
Q

define absorption of drug

A

= movement from site of administration into plasma

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5
Q

factors that effect absorption of drug x9

A
  1. lipid solubility (molecular weight & structure pKa)
  2. surface area
  3. gut content
  4. GI transit time (food, dioheara, vomiting)
  5. blood flow at site of administration
  6. drug interaction
  7. age
  8. health status
  9. genetic polymorphisms
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6
Q

what type of molecules can freely cross a membrane

A

molecules in which electrons are uniformly distributed = unionised

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7
Q

if the pKa of acetic acid is 5 and the pH of the environment is 1 is the environment basic or acidic

A

protonated = acidic - drug can cross the membrane

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8
Q

if the pKa of acetic acid is 5 and the pH of the environment is 8 is the environment acidic or basic

A

deprotonated = basic - drug can’t cross membrane

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9
Q

if the drug is more basic is it able to travel through the membrane

A

no

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10
Q

why do weak acids get trapped in the cell

A

because it means they usually have a pKa of around 4.4 meaning the environment pH is usually higher at around 7 which means they are trapped because it is in the ionised form as a basic acids

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11
Q

the higher the pH

A

facilitates dissociation

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12
Q

the lower the pH

A

reduces dissociation

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13
Q

what does the Henderson-Hasselbalch equation allow us to predict

A

we can calculate the unionised amount of the drug which means we can predict the absorption of the drug, and where the drug can be trapped depending on the pH of the environment

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14
Q

routes of administration

A 
o	Oral 
o	Sublingual 
o	Rectal 
o	Application to other epithelial surfaces (e.g., skin, cornea & vagina)
o	Inhalation (pulmonary)
o	Injection 
o	Subcutaneous (SC) – insulin 
o	Intramuscular (IM) – covid 
o	Intravenous (IV)
o	Intra-arterial 
o	Intrathecal & intravitreal
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15
Q

define parameter

A

a measurable factor forming one of a set that defines a system or sets the conditions of its operation

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16
Q

what are the parameters in pharmacokinetics

A
  1. C max
  2. T max
  3. peak absorption phase
  4. peak elimination phase
  5. above therapeutic range
  6. bioavailability
  7. volume of distribution
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17
Q

define area under a curve

A

provides a measure of drug exposure

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18
Q

define bioavailability

A

important parameter to inform the fraction of the drug that has reached the systemic circulation = blood plasma = NOT THE ACTUAL SITE = drug unaltered from entering the site of administration

19
Q

if 100% of the does of drug enters the systemic circulation the bioavailability is

A

1.0

20
Q

the fraction is equal to

A

the quantity of drug reaching the systemic circulation divided by the quantity of drug administered

21
Q

factors that may affect drug bioavailability

A
  1. first-pass metabolism = broken down/altered before destination, enzymes released from bacteria could break down drugs
  2. neglects rate of absorption
  3. gastic pH
  4. intestinal motility
22
Q

how can absorption characteristics change even though the same drug is administrated

A

the formation of the drug e.g. oral or intravenous

23
Q

factors that affect drug distribution x9

A
  1. large drug
  2. polar drug
  3. drug enriched in fat
  4. permeability across tissue barriers
  5. binding within compartments
  6. pH partition
  7. fat: water partition
  8. blood flow to the tissue = takes more to get to toes
  9. protein binding
24
Q

how much of our body is water (percentage)

A

50-70%

25
Q

the four main compartments

A
  1. plasma
  2. interstitual fluid
  3. intracellular fluid
  4. transcellular fluid
26
Q

effect of drug binding to protein

A
  • Only the free or unbound drug fraction exerts pharmacological effects meaning if someone is low on the protein that binds then the dose could be too much and cause toxicity
  • If bound to protein more likely to stay in the blood stream
27
Q

what happens if too much drug compared to protein

A

not enough protein to bind to the drug meaning more drug is active meaning could cause toxicity

28
Q

define volume of distribution

A

= the volume of fluid into which a drug appears to be distributed or diluted

29
Q

the equation for Vd

A

Vd = amount of drug in the body (mg) divided by the plasma concentration of drug (mg/L)

30
Q

high Vd means

A

more of the drug is in the tissues

31
Q

factors affecting Vd

A
  1. age
  2. gender
  3. body composition
  4. presence of disease
32
Q

apparent plasma volume

A

about 0.5L/kg body weight (approx. 4L)

33
Q

apparent the extracellular volume

A

about 0.2L/kg

34
Q

apparent total body water

A

about 0.55 L/kg (approx. 42L)

35
Q

most drugs are designed to be…(pH level)

A

weak acids & bases

36
Q

is a drug that is protonated or deprotonated easier to cross a membrane ?

A

protonated

37
Q

when the pH is lower then the pKa of the compound does that make the environment acidic or basic ?

A

acidic

38
Q

pKa define

A

the pH at which 50% of the drug is in its ionised form

39
Q

if the drug is an acid and protonated (due to the environment) then the acid is …

A

unionised

40
Q

example of drug diffusing from gastrointestinal tract

A

if the drug is a weak acid (4.4), the gastic juice pH is high (1.2), thus, the drug can cross the membrane. however, once the drug is in the plasma, due to the low plasma pH (7.4) the drug becomes deprotonated and ionised meaning it cannot cross back, meaning the drug is trapped in plasma. this is good because then it has to then be absorbed into tissue to have effect.

41
Q

define absorption

A

refers to the ability for drug to cross the gut wall into the portal vein

42
Q

difference between poor oral availability and high first pass metabolism

A

poor oral availability - the drug isn’t absorbed from the gastrointestinal tract into the portal vein. instead it keeps going through intestines and is excreted

high first pass metabolism - the drug is absorbed into the portal vein from the gastrointestinal tract but when goes into the liver a high amount is metabolised and less leaves the liver = affects bioavailability

43
Q

vd unit

A

L

phar24 (12 decks)

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