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Pharmacy > the Science of Medicines > Flashcards

the Science of Medicines Flashcards

1
Q

Why do we need to study the solubility of drugs?

A

there are changes in pH within the GI tract, so changes in ionisation and solubility and drugs could precipitate

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2
Q

Henderson-Hasselbalch equation for a weak acid

A

log [A-] / [HA] = pH - pKa

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3
Q

When is [A-] greater than [HA]?

A

when pH is greater than pKa

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4
Q

When is [HA] greater than [A-]?

A

when pH is less than pKa

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5
Q

Henderson-Hasselbalch equation for a weak base

A

log [B] / [BH+] = pH - pKa

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6
Q

When is [B] greater than [BH+]?

A

when pH is greater than pKa

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7
Q

When is [BH+] greater than [B]?

A

when pH is less than pKa

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8
Q

What is the solubility of a weak acid like in low pH?

A

you decrease pH by adding H+, so there will be an increased proportion of HA, which is unionised, so low solubility

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9
Q

What is the solubility like of a weak acid at high pH?

A

you increase pH by removing H+, so higher proportion of ionised form, which is highly soluble

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10
Q

Weak acid as salt equilibrium equation

A

Na+ A- + H2O <=> NaOH + HA

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11
Q

What is S0?

A

the saturation solubility of the undissociated species HA

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12
Q

What is Cs?

A

the ‘total saturation solubility’ of the weak acidic drug –> interpreted as the initial concentration of salt added to solution

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13
Q

What does Cs equal?

A

Cs = S0 + [A-]

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14
Q

What information do you need to predict the solubility of a weakly acidic drug?

A
  1. pH of the solution
  2. the pKa
  3. the solubility of the free (unionised) form of the drug (S0)
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15
Q

What is the solubility equation for a weakly acidic drug?

A

log (Cs-S0) / S0 = pH - pKa

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16
Q

When pH = pKa, what is the Cs of a weakly acidic drug?

A

Cs = 2 x S0

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17
Q

The solubility of a weakly acidic drug increase by about …. for each pH unit above the pKa

A

10x

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18
Q

The solubility of a weakly acidic drug approaches S0 as….

A

pH decreases below the pKa

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19
Q

The solubility of a weakly acidic drug equal 2 x S0 when…

A

the pH equals the pKa

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20
Q

When is a weakly basic drug more soluble?

A

when pH is decreased by adding H+, so there is an increased proportion of BH+, so higher solubility

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21
Q

When is a weakly basic drug less soluble?

A

when pH is increased by removing H+, so there is a smaller proportion of BH+ and higher of B, so lower solubility

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22
Q

Equation for weak bases forming salts

A

BH+ Cl- + H2O <=> B + H+ Cl- + H2O

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23
Q

What is Cs equal to for a weakly basic drug?

A

Cs = S0 + [BH+]

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24
Q

When pH = pKa, what is the Cs of a weakly basic drug?

A

2 x S0

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25
Q

The solubility of a weakly basic drug increases by about … for each unit of pH below the pKa

A

10x

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26
Q

The solubility of a weakly basic drug approaches S0 as…

A

the pH increases above the pKa

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27
Q

The solubility of a weakly basic drug equals 2 x S0 when…

A

pH = pKa

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28
Q

What happens to the pH of a solution when the salt of a weak acid is used instead of the free form?

A

the pH increases

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29
Q

What happens to the solubility to the salt of a weak acid instead of the free form?

A

solubility increases

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30
Q

When may the precipitation of the salt of a weak acid occur?

A

when pH is the solution is lowered

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31
Q

What happens to the pH of the solution of the salt of a weak base instead of the free form?

A

the pH of the solution decreases

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32
Q

What happens to the solubility of the salt of a weak base instead of the free form?

A

solubility increase

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33
Q

When may precipitation occur with the salt of a weakly basic drug?

A

if pH is increased

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34
Q

BCS class 1

A

high solubility and permeability, use simple solid oral dosage form

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35
Q

BCS class 2

A

low solubility, high permeability, need techniques to increase surface area OR use solvents or surfactants

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36
Q

BCS class 3

A

high solubility, low permeability, need to include permeability enhances

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37
Q

BCS class 4

A

low solubility and permeability, combine 2 and 3

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38
Q

What happens to a weak base in the GI tract?

A

it will have a high dissolution rate in the stomach, but this falls as the pH of the GI tract rises

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39
Q

What happens to a weak acid in the GI tract?

A

it will have minimal dissolution in the stomach as pH is so low, but it increases down the gut with pH

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40
Q

How does the salt of a weak acid increase the pH of the diffusion layer?

A
  1. Na+ + Cl- + H2O  Na+ + OH- + HA
  2. Cl- reacts with water, forming -OH, increasing pH
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41
Q

How does the salt of a weak base decrease the pH of the diffusion layer?

A
  1. BH+ + Cl- + H2O = H2O + B + H+ + Cl-
  2. BH+ can donate a proton to water through H30+, which forms H2O and H+, increasing pH
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42
Q

What is the major advantage of using the salt form of a drug?

A

results in a controlled pH of the diffusion layer no matter where in the GI tract it is

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43
Q

When does precipitation of a drug occur?

A

when the pH of solution is adjusted to a value that produces mostly unionised molecules exceeding solubility

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44
Q

How can the solubility of non-polar compounds in water be improved?

A

adding water-miscible solvents in which the compound IS soluble

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45
Q

define co-solvent

A

vehicles used with water to increase the solubility of a drug

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46
Q

What is the purpose of cosolvents? (3)

A
  1. get aqueous systems where the drug is more soluble
  2. formulate higher concentrations of the drug
  3. improve stability of the formulation
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47
Q

What are the 3 factors a cosolvent needs?

A
  1. to be an organic compound
  2. miscible with water
  3. better solvent than water for the drug
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48
Q

How do cosolvents works?

A
  1. they decrease the hydrogen bond density of the aqueous system
  2. reduce the cohesive interactions of water
  3. reduce the polarity of the solution
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49
Q

How does solubility increase with increasing cosolvent concentration?

A

exponentially

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50
Q

define interfacial area

A

the total area of contact between two liquids in a liquid-liquid operation –> large one will prevent dissolving

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51
Q

How do inclusion compounds work?

A

by incorporating the non-polar portion of one molecule into the non-polar part of another molecule that is water soluble –> you reduce the non-polar water interfacial area by inserting the solute into the complexing agent

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52
Q

What is the most commonly used inclusion compouns?

A

cyclodextrins

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53
Q

What is a cyclodextrin?

A

an enzymatically modified starch, and their units form a cylindrical ring

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54
Q

What is the structure of a cyclodextrin?

A

the outer surface of the ring is hydrophobic and the internal surface of the cavity is non-polar

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55
Q

define surface tension

A

adhesive forces between the liquid phase of one substance and either a solid, liquid or gas phase of another surface at the interface

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56
Q

How do surfactants work?

A

they reduce the surface tension at an interface without needing large concentrations of them

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57
Q

To be a surfactant, what properties are needed?

A
  1. one element must have a high affinity for the solvent (hydrophilic or polar head, non-ionic or ionic)
  2. one element must have a minimal affinity for the solvent (lipophilic or nonpolar chain)
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58
Q

What must the polar region on a surfactant be able to do?

A
  1. have an affinity for water
  2. must be capable of pulling long-chain hydrocarbons into water
  3. must be polar enough to hold the nonpolar region of the surfactant in solution
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59
Q

How are surfactants classified?

A

by the charge carried by polar part: anionic, cationic, zwitterionic, non-ionic

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60
Q

define critical micelle concentration

A

the concentration of monomer (surfactant) at which micelles form

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61
Q

define aggregation number

A

the number of monomers that aggregate to form a micelle

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62
Q

At the critical micelle concentration, which physical properties of surfactants change?

A
  1. osmotic pressure
  2. turbidity
  3. electrical conductance
  4. surface tension
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63
Q

What factors of surfactants may increase the critical micelle concentration?

A

decrease the carbon chain length, increase the polarity of the head

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64
Q

What factors of surfactants may decrease the critical micelle concentration?

A

temperature, pH, a second surfactant, addition of electrolytes, longer carbon chain length

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65
Q

What are the 4 critical values for micelles?

A
  1. critical micelle concentration
  2. Kraft point (critical micelle temperature)
  3. cloud point
  4. critical micelle pH
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66
Q

define the Kraft point

A

the temperature at which the solubility becomes equal to the critical micelle concentration

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67
Q

What happens when temperature is less than the Kraft point?

A

the critical micelle concentration is greater than the solubility, so micelles can’t form

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68
Q

What happens when temperature is greater than the critical micelle concentration?

A

the surfactant forms micelles

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69
Q

What happens to micelles at the cloud point?

A

an increase in temperature leads to dehydration of POE chains, decreased water solubility and the formation of very large micelles making the solution cloudy

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70
Q

What happens at the critical micelle pH?

A

if the ionised form of a compound is surface active and the unionised form is surface inactive (or has a lower CMC than the ionised form) then a change in pH can induce micellisation

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71
Q

Can the polar part of a surfactant be non-ionic?

A

yes, for example hydroxyl and ether groups

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72
Q

What do surfactants do?

A

decrease the surface tension at the interface

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73
Q

What is the downside to non-ionic polar heads?

A

they are less polar than ionised groups, so we need more ‘units’ to produce an effective polar head

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74
Q

What is polyoxyethylene (POE)?

A

a chain with 20 or more ether groups linked to the nonpolar part

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75
Q

What does POE-23 lauryl ether mean?

A

there are 23 monomeric POE groups in this molecule

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76
Q

What are the applications of anionic surfactants?

A

oil/water emulsifiers

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77
Q

What are the applications of cationic surfactants?

A

disinfectants, oil/water emulsifers

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78
Q

What are the applications of non-ionic surfactants?

A

oil/water and water/oil emulsifiers, also have low toxicity unlike cationic and anionic

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79
Q

Can surfactants be used as drugs?

A

yes

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80
Q

When does micellisation occur?

A

when micelle concentration exceeds the CMC

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81
Q

define solubilisation

A

the process by which water-insoluble or partly soluble substances are brought into aqueous solution by incorporation into micelles

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82
Q

What is the solubilisation capacity (k)?

A

a measure of the ability of a surfactant to solubilise a solute

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83
Q

What is the molar solubilisation capacity (k)?

A

the number of moles of solute that can be solubilised by 1 mole of micellar surfactant

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84
Q

What are the equations for solubilisation capacity?

A

k = molar solubility of the solute in the micelle / molar concentration of micellar surfactants

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85
Q

Why is a low CMC for surfactant drugs preferred?

A

low CMC means that the surfactant can form micelles at a lower concentration, so when micelles are formed they can solubilise hydrophobic drugs

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86
Q

How can we increase the solubilisation capacity of a low polarity solute?

A
  1. increase hydrocarbon chain -> larger nonpolar regions will solubilise more solute and decreases CMC
  2. introduce polar group
  3. used branched surfactants as they form smaller micelles
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87
Q

What 4 factors need to be considered when selecting a surfactant?

A
  1. amount of surfactant that can be placed in water
  2. ability of it to solubilise the solute
  3. the chain length -> influences CMC
  4. finding a balance
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88
Q

What is Lundelius’ rule?

A

any factor that decrease the solubility of the surfactant promotes surface activity

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89
Q

What does a high HLB surfactant value indicate?

A

a surfactant with mainly polar or hydrophilic properties

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90
Q

What does a low HLB surfactant value indicate?

A

surfactant with mainly lipophilic or non-polar properties

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91
Q

How do you calculate the HLB of a mixture of surfactants?

A

HLB = x HLB(A) + (1-x) HLB(B) where x are fractions of each surfactant

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92
Q

define required HLB

A

the particular HLB of a surfactant needed to form a stable w/o or o/w emulsion

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93
Q

Why does HLB of an emulsifier vary with temperature?

A

temperature affects the relative solubilities of the lipophilic and hydrophilic parts

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94
Q

What happens to non-ionic surfactants at higher temperature?

A

hydrogen bonds are weakened by thermal forces and the emulsifier is less soluble in water

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95
Q

define the Phase Inversion Temperature (PIT)

A

the T at which an emulsifier changes from being an O/W emulsifier to a W/O emulsifier

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96
Q

If a non-ionic emulsifier is water soluble at low temperature, what kind is it?

A

it stabilises O/W emulsions

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97
Q

If a non-ionic emulsifier is oil soluble at high temperature, what kind is it?

A

it stabilises W/O emulsions

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98
Q

define swallowing

A

the passage of a food bolus from the oral cavity to the stomach

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99
Q

What muscles does swallowing involve?

A

muscles in the oral cavity, pharynx, larynx and oesophagus

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100
Q

What are the 3 phases of swallowing?

A

oral, pharyngeal, oesophageal

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101
Q

What are the steps of swallowing?

A
  1. stimulated when a food bolus stimulates pressure receptors in the back of the throat and larynx
  2. signals to the swallowing centre in the brain
  3. swallowing centres trigger nerve impulses
  4. this stimulates skeletal muscles in the pharynx and upper oesophagus
  5. involuntary contraction in the pharyngeal muscles pushes material into the oesophagus
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102
Q

What are the 2 types of movement in the stomach?

A

churning, peristalsis

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103
Q

When food is mixed, what are the stomach contents referred to as?

A

chyme

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104
Q

What does peristalsis in the stomach cause?

A

opening of the pyloric sphincter

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105
Q

What does the rate of gastric emptying depend on?

A

viscosity of chyme

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106
Q

How does movement in the stomach affect drugs?

A

churning is involved in dissolution and gastric emptying rate influences drug absorption

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107
Q

What happens to a drug if there is delayed gastric emptying?

A

the drug stays in the stomach and affect its stability as it is in acid for longer

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108
Q

What are the two types of movement in the small intestine?

A

segmentation (causes mixing) and peristalsis

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109
Q

What is peristalsis in the small intestine coordinated by?

A

the enteric nervous system

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110
Q

define segmentation

A

when non-adjacent segments of the small intestine alternately contract and relax, moving the food forwards then backwards

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111
Q

What are the steps of peristalsis in the small intestine?

A
  1. contraction of circular muscles behind food mass
  2. contraction of longitudinal muscles ahead of food mass
  3. contraction of circular muscle again forces food mass forward
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112
Q

What does the enteric nervous system control?

A

intestinal and colonic motility

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113
Q

What are the 2 main branches of neurones in the ENS?

A

Auerbach’s (myenteric) plexus and Meissner’s (submuscosal) plexus

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114
Q

What is the ENS influenced by?

A

neurotransmitters and autonomic input

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115
Q

How does the sympathetic NS affect the ENS?

A

inhibits the ENS -> decreases peristalsis, blood flow, secretion and absorption

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116
Q

How does the parasympathetic NS affect the ENS?

A

stimulates ENS -> increases peristalsis, blood flow, secretion and absorption

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117
Q

Which hormones increase activity of the ENS?

A

gastrin, motilin, serotonin, insulin, cholecystokinin

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118
Q

Which hormones decrease the activity of the ENS?

A

secretin and glucagon

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119
Q

How does intestinal motility affect drug absorption?

A
  1. transit time -> influences absorption
  2. distribution -> contractions in GI tract increase SA of drug
  3. migrating mobility complex -> involved in regulating drug absorption
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120
Q

define migrating motility complex

A

a recurring motility pattern that is regulated by electrical activity

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121
Q

When does migrating motility complex occur?

A

between feeding

122
Q

What is the function of the migrating motility complex?

A

used to get rid of undigested food -> cleansing mechanism

123
Q

How can the migrating motility complex affect drug administration?

A

if people take drug with an empty stomach, then it helps it pass through the body quickly and be absorbed quicker

124
Q

What are the 2 types of motility in the large intestine?

A

haustral shuttling and mass movement

125
Q

How does haustral shuttling work?

A

done by localised contraction and relaxation of haustra (bands) and occurs all the time

126
Q

What is mass movement?

A

coordinated contraction of the intestine that moves the contents of the colon towards the rectum

127
Q

Where does mass movement occur?

A

ascending and transverse colon

128
Q

What is mass movement triggered by?

A

the gastrocolic reflex that signals to your body that you need to defaecate

129
Q

What causes constipation?

A

weak mass movement, increased transit time, too much water absorbed into the body

130
Q

What causes diarrhoea?

A

hyperactive mass movement, decreased transit time, too little water absorbed into the body

131
Q

define vomiting

A

forcible expulsion of gastric contents through the mouth

132
Q

Where are signals relayed for vomiting to?

A

the vomiting centre in the brainstem

133
Q

What are the steps of vomiting?

A
  1. increase salivation to protect teeth
  2. relaxation of the lower oesophagael sphincter to allow contents to move up
  3. contraction of diaphragm and abdominal muscles to increase pressure in stomach
  4. opening of the uppoer oesophageal sphincter
134
Q

mouth and oesophagus role in motility

A

chewing, swallowing, peristalsis

135
Q

stomach role in motility

A

churning, peristalsis, gastric emptying

136
Q

small intestine role in motility

A

segmental contractions, peristalsis

137
Q

large intestine role in motility

A

haustral shuttling, mass movement, defaecation

138
Q

sphincters role in motility

A

regulation of movement

139
Q

define digestion

A

the sequence by which food is broken down and chemically converted so that it can be absorbed by the cells of an organism

140
Q

What are the 2 types of digestion?

A

mechanical and chemical

141
Q

What are the 4 sites of digestion?

A
  1. mouth
  2. stomach
  3. small intestine
  4. large intestine
142
Q

What are the secretions from the salivary glands?

A

amylase, ligual lipase, mucus

143
Q

Which type of cell secretes amylase in the salivary glands/

A

serous cells

144
Q

What happens to amylase in the stomach?

A

it is inactivated due to low pH

145
Q

Which cell is ligual lipase secreted from?

A

serous cells

146
Q

What does ligual lipase do?

A

breaks down lipids and is NOT degraded in the stomach

147
Q

Why are mucous cells in salivary glands important?

A

they secrete mucus to lubricate food and protect the mouth from stomach acid

148
Q

What are the 4 types of cells that secrete substances in the stomach?

A
  1. parietal cells
  2. chief cells
  3. mucous cells
  4. G cells
149
Q

What do parietal cells do?

A

they secrete HCl and release pepsinogen, which is cleaved to pepsin

150
Q

What do chief cells do?

A

secrete pepsinogen also, which is cleaved to pepsin to digest proteins

151
Q

What do mucous cells do?

A

secrete mucous for lubrication and protection of food from acid

152
Q

What do G cells do?

A

produce gastrin

153
Q

What is gastrin?

A

a hormone involved in regulating the release of HCl

154
Q

What are the 4 main secretions from the stomach?

A

pepsinogen, HCl, gastrin, mucus

155
Q

What is gastric acid production stimulated by?

A

histamine, gastrin, acetylcholine

156
Q

What cells does gastric acid production involve?

A

parietal cells, G cells, enterochromaffin cells

157
Q

What does the gallbladder do?

A

collects bile from the liver and concentrates it -> bile then passes through bile duct into small intestine

158
Q

What does the pancreas secrete?

A
  1. bicarbonate (neutralise stomach acid)
  2. lipase
  3. amylase
  4. RNAase and DNAase
  5. trypsinogen, chymotrypsinogen
159
Q

How is the digestive process initiated and controlled?

A
  1. stretch receptors in the stomach trigger secretion of digestive enzymes and juices
  2. the stomach releases gastrin, which causes proudction of gastric acid
  3. intestines release secretin and cholecystokinin to stimulate the secretion of pancreatic juice and bile
160
Q

How is the small intestine adapted for absorption?

A

cells have projections called villi, which contain microvilli, giving a large SA

161
Q

What is the route of absorption for sugar and amino acids?

A

absorbed directly into the bloodstream

162
Q

How is absorption of fats different?

A

they are absorbed into the lymph lacteal system

163
Q

What are the 2 main mechanisms of absorption?

A

active transport and facilitated diffusion

164
Q

Where are proteins digested and by which enzymes?

A
  1. stomach -> pepsin
  2. pancreas -> trypsin and chymotrypsin
  3. intestinal brush border -> peptidases
165
Q

How are proteins absorbed?

A

by active transport into the gut cells, then by diffusion into the bloodstream

166
Q

Where are carbohydrates digested and by which enzymes?

A
  1. mouth -> salivary amylase
  2. small intestine -> pancreatic amylase
  3. enzymes in the intestinal brush border
167
Q

Where does carbohydrate digestion stop?

A

in the stomach as the stomach acid denatures amylase

168
Q

How are carbohydrates absorbed?

A

by facilitated diffusion and active transport

169
Q

Where is fat digested and by which substances/enzymes?

A
  1. small intestine -> secretions from liver, pancreas and gallbladder to emulsify
  2. gallbladder and pancreas -> lipase and bile
170
Q

How are lipids absorbed?

A
  1. lipids are broken down into fatty acids
  2. fatty acids absorbed into epithelial cells of small intestine
  3. they are coated with cholesterol, phospholipids and protein to form chylomicron
  4. chylomicron is water soluble and can enter the lacteal system
  5. transported to bloodstream
171
Q

What does an enteric coating do?

A

prevents degradation of drugs in the stomach by protecting them from gastric acid -> allows them to be release in the small intestine

172
Q

What is an enteric coating made from?

A

a gastric resistant polymer which is insoluble at low pH

173
Q

Anatomically, how many lobes does the liver have? What are they called?

A

4 = left, right, caudate, quadrate

174
Q

define diaphragmatic surface

A

the upper surface of the liver that sits underneath the diaphragm

175
Q

define visceral surface

A

the lower surface of the liver that faces the abdominal organs and gallbladder

176
Q

How is bile removed from the liver?

A

the bile duct feeds into the gallbladder, which joins the pancreatic duct and empties into duodenum of small intestine

177
Q

What are Kupffer cells?

A

immune cells in the liver

178
Q

What are the 3 blood vessels connected to the liver?

A

hepatic artery (oxygenated blood from heart), hepatic portal vein (little oxygen from GI tract), hepatic vein

179
Q

What are the 6 main functions of the liver?

A
  1. endocrine function
  2. exocrine function
  3. clotting
  4. cholesterol metabolism
  5. organic and drug metabolism
  6. secretion of plasma proteins
180
Q

What is the exocrine function of the liver?

A

secretes bile salts and HCO3-

181
Q

What do hepatocytes secrete?

A

bile, cholesterol, phospholipids

182
Q

What is bile made up of?

A

bile salts

183
Q

What are bile salts important for?

A

solubilising fats

184
Q

What is bilirubin?

A

byproduct of breakdown of red blood cells

185
Q

What do epithelial cells secrete?

A

bicarbonate

186
Q

What happens to bile during a meal?

A

the body must prepare to digest fats, to the gallbladder contracts and releases bile into the duodenum via the sphincter of Oddi

187
Q

What is contraction of the gallbladder stimulated by?

A

cholecysotkinin which is triggered by fatty acids

188
Q

define enterohepatic circulation

A

when the liver extracts bile salts from the blood and secretes them back into the bile to prevent having to synthesise them constantly

189
Q

Where are small amounts of bile lost to?

A

faecas and urine

190
Q

What are new bile salts synthesised from?

A

cholesterol

191
Q

What happens to bile salts during a meal?

A
  1. bile salts are absorbed into the small intestine by Na+ coupled transporters
  2. most is then returned to the liver through the hepatic portal vein via enterohepatic circulation
192
Q

What does dietary fibre do to cholesterol?

A

it conceals the bile in the small intestine to prevent it returning to the liver and it is removed from the body with the cholesterol it contains

193
Q

What are the functions of cholesterol?

A
  1. membrane synthesis
  2. bile synthesis
  3. precursor for steroid hormones
194
Q

Where and how is cholesterol synthesised in the body?

A

in the liver by HMG-CoA

195
Q

How are cholesterol levels maintained in a normal range?

A

increasing dietary cholesterol or suppressing HMG-CoA

196
Q

What do saturated fatty acids do?

A

increase plasma cholesterol

197
Q

What do poly/monounsaturated fatty acids do?

A

decrease plasma cholesterol

198
Q

How does cholesterol circulate in the body?

A

in lipoprotein complexes

199
Q

What do low density lipoproteins do (LDLs)?

A

deliver cholesterol to cells

200
Q

What do high density lipoproteins (HDLs) do?

A

remove cholesterol from plasma and deliver it to the liver

201
Q

What is atherosclerotic disease caused by?

A

deposition of cholesterol in the artery walls, increasing risk of heart attack

202
Q

What increases HDL?

A

smoking

203
Q

What increases HDL?

A

weight loss, oestrogen (until menopause)

204
Q

What are gallstones caused by?

A

cholesterol crystallising out of bile salts in the gallbladder

205
Q

What do gallstones cause?

A
  1. they block the gallbladder and bile duct
  2. prevents fat digestion and causes fat build up in the gut -> diarrhoea
  3. decrease in absorption of fat-soluble vitamins, clotting issues and calcium deficiency
206
Q

What are the endocrine functions of the liver?

A
  1. synthesis of hormones and peptides
  2. synthesis of plasma proteins
  3. synthesis of clotting factors
207
Q

How is the liver important in clotting?

A
  1. bile absorbs fats, which absorb vitamin K
  2. vitamin K is needed for prothrombin production
  3. this is a precursor for thrombin
208
Q

What is hepatitis caused by?

A

viruses or excessive alcohol intake

209
Q

What is liver cirrhosis caused by?

A

drugs, alcohol, viruses

210
Q

In liver function blood tests, what do raised levels of liver enzymes indicate?

A

liver damage -> most of the enzymes should be in hepatocytes, but are detected in blood

211
Q

Which compounds are used in liver function tests?

A
  1. alanine transaminase (ALT)
  2. aspartate aminotransferase (AST)
  3. alkaline phosphatase (ALP)
  4. gamma-glutamyltransferase (GGT)
  5. bilirubin
  6. albumin
212
Q

What does any raised hepatocyte enzyme indicate?

A

liver cell damage

213
Q

What does an AST:ALT ration above 2:1 indicate?

A

alcoholic liver disease

214
Q

What do raised levels of ALP indicate?

A

bone disease

215
Q

What do raised levels of GGT indicate?

A

alcohol excess

216
Q

What do raised levels of ALP and GGT indicate?

A

obstruction of the bile duct

217
Q

define elimination

A

the removal of a substance or termination of its biological action

218
Q

In which two ways does elimination of substances in the body occur?

A
  1. metabolism
  2. excretion
219
Q

define anabolism

A

the build-up of compounds

220
Q

define catabolism

A

breakdown of compounds

221
Q

Which organs are responsible for removal of substances?

A
  1. liver
  2. kidneys
  3. lungs
222
Q

What are the aims of the phase I and phase II reactions in the liver?

A

to decrease lipid solubility and enhance renal elimination

223
Q

How do molecules reach the liver?

A

through the hepatic artery and portal vein

224
Q

What are the steps of enterohepatic circulation?

A
  1. compounds from the liver are secreted into the bile
  2. most are then reabsorbed in the small intestine
  3. circulated back to the liver
225
Q

What do liver enzymes do to lipophilic molecules?

A

metabolise them to form polar products so they can be excreted in the urine

226
Q

What are the two stages of liver metabolism?

A

Phase I and Phase II

227
Q

What happens in phase I to molecules?

A

catabolic reactions and introduction of a functional group which adds as a ‘tag’ to provide a point of conjugation for phase II

228
Q

What are the main mechanisms of catabolism in phase I?

A

oxidation, reduction, hydrolysis

229
Q

Which enzymes carry out the phase I reaction?

A

liver microsomal enzymes from the cytochrome P450 family (CYP enzymes)

230
Q

What type of molecule does liver metabolism deal with? Why?

A

mainly applicable to lipid soluble molecules as polar molecules can be excreted at least partly unchanged

231
Q

How does cytochrome P450 enzymes differ?

A

they have different..
1. amino acid sequences
2. substrate specificity
3. susceptibility to inducers and inhibitors

232
Q

define polymorphic form (enzymes)

A

an enzyme that exist in multiple different forms within the same species

233
Q

What determines your cytochrome P450 enzymes?

A

different alleles in your genes -> different amino acid sequences

234
Q

What does an individuals cytochrome P450 enzymes affect?

A

the rate of activity of the enzymes, therefore creates differences in side effects and drug response

235
Q

What happens in phase II?

A

anabolism and involves the addition of a subtituent group to inactive the compound

236
Q

What are examples of substituent groups added?

A

glucuronyl, sulphate, methyl, acetyl

237
Q

What happens to the product after phase II?

A

several hydrophilic products are secreted into the bile and delivered to the small intestine where the conjugation and the drug is reabsorbed

238
Q

What different processes do different enantiomers undergo?

A
  • different pharmacological effects on receptors
  • they are metabolised differently
239
Q

What are the steps of pre-systemic first-pass metabolism?

A
  1. food and drugs are absorbed into small intestine and pass into the blood
  2. the blood is carried to the liver by the hepatic portal vein
  3. so hepatic microsomal enzymes can metabolise food or drugs before entering systemic circulation
240
Q

For drugs administered by IV, is a higher or lower dose needed?

A

lower –> as there is no initial metabolism as drug goes straight into systemic circulation

241
Q

For patients with less GI motility, is a higher or lower dose needed?

A

high dose as less absorption of drug into bloodstream

242
Q

For patients with decreased liver function, is a higher or lower dose needed?

A

lower as there is less metabolism of the drug and metabolites may be toxic

243
Q

define prodrug

A

a drug that is inactive when administered and is only activated when it is metabolised

244
Q

define single nucleotide polymorphism

A

a DNA sequence variation with a different single nucleotide at a particular locus

245
Q

What are the effects of SNPs on CYP450 enzymes?

A

the different nucleotide sequence may change the amino acid sequence

246
Q

What do different polymorphic forms of enzymes lead to?

A

different rates of enzymatic activity and metabolism

247
Q

fast metaboliser and active drug

A

higher dose needed

248
Q

fast metaboliser and prodrug

A

lower dose needed as increased risk of toxic effect as fast activation

249
Q

slow metabolisers and active drug

A

lower dose needed as metabolised slower -> may be toxic

250
Q

slow metabolisers and prodrug

A

higher dose needed as prodrug will not be active for long

251
Q

How are CYP450 profiles of patients roughly determined?

A

start patients on a low dose of the drug and take blood samples to find the amount of active drug in the blood and increase from there

252
Q

Do CYP450 inducers make drugs work faster or slower?

A

faster as they increase the activity of the enzymes so drug is broken down and cleared quicker

253
Q

What are 3 inducers of CYP450 enzymes?

A

brussel sprouts, smoking, St John’s Wort

254
Q

What is an inhibitor of CYP450 enzymes?

A

grapefruit juice

255
Q

How do co-administered drugs affect each other?

A

many drugs can compete as substrates for CYP450 enzymes so affect the metabolism of each other

256
Q

What do CYP450 enzyme inducers do?

A

increased the activity of the enzymes, so increase rate of metabolism

257
Q

What are the drawbacks of enzyme inducers?

A
  1. a single co-administered drug may be metabolised too quick reducing its effect
  2. toxic metabolites will increase
258
Q

What 3 main factors affect CYP450 enzymes?

A

genetic polymorphisms, diet and co-administered drugs

259
Q

What are the 5 main functions of the kidneys?

A
  1. regulation of water, salts, acidity
  2. removal of metabolic waste
  3. removal of foreign chemicals e.g. drugs
  4. gluconeogenesis
  5. production of hormones and enzymes
260
Q

Name 2 enzymes the kidneys produce

A

erythropoietin (controls RBC production and renin (controls blood pressure and Na+ balance)

261
Q

What are the 4 regions of the kidney?

A
  1. capsule -> boundary separating it
  2. cortex -> outer region where nephrons sit
  3. medulla -> inner region
  4. pelvis -> feeds into the ureter
262
Q

What happens in the Bowman’s capsule?

A

blood is filtered

263
Q

What happens in the loop of Henle?

A

main site of water reabsorption

264
Q

What are the 3 stages of nephron function and filtering by the kidneys?

A
  1. glomerular function
  2. tubular function
  3. tubular reabsorption
265
Q

define tubular secretion

A

the process by which the kidneys move substances from the blood into the tubules

266
Q

define tubular rebabsorption

A

the process by which the kidneys remove water and solutes from the filtrate and return them to the bloodstream

267
Q

How does the structure of the glomerulus allow for much filtration to happen?

A

the vessel is ‘bunched up’, so blood spends a long time within the vessel inside the Bowman’s capsule

268
Q

How are cells in the glomerulus adapted?

A

the endothelial cells have tiny pores, so are leaky

269
Q

define podocyte

A

specialised cells on the outside of the glomerular capillary with many small projections to create sieve like structure

270
Q

define glomerular filtration rate

A

the volume of fluid filtered from the glomeruli to the Bowman’s capsule per unit of time

271
Q

How is the GFR regulated?

A

by the body adjusting the blood pressure on either side of the glomerulus

272
Q

How is the glomerular filtration rate reduced?

A

constrict the afferent arteriole or dilate the efferent arteriole to reduce pressure

273
Q

How is the glomerular filtration rate increased?

A

dilate the afferent arteriole or constrict the efferent arteriole to increase the pressure -> increases the excretion of water and salt

274
Q

Where is Na+ (salt) reabsorbed?

A
  1. proximal convoluted tubule
  2. loop of Henle
  3. the collecting duct
275
Q

Which regions does salt go through to be reabsorbed into the blood?

A

tubule fluid -> tubule cell -> interstitial space -> blood

276
Q

How does reabsorption of Na+ from the tubule fluid to tubule cells occur (proximal convoluted tubule)?

A

via cotransporters and counter-transporters

277
Q

define cotransporter

A

a membrane protein that moves two different molecules or ions across a cell membrane at the same time in the same direction

278
Q

define counter-transporter

A

a membrane protein that moves two or more molecules in opposite directions across a cell membrane

279
Q

What is the main counter-transporter found at this stage?

A

Na+ pumped into cell, H+ pumped out

280
Q

How does rebabsorption of Na+ from the tubule cells to interstitial space occur (proximal convoluted tubule)?

A

active transport by Na+/K+ ATPase

281
Q

What is Na+/K+ ATPase?

A

Na+/K+-ATPase pumps three sodium ions out of the cell into interstitial space and two potassium ions into cell -> Na K pump

282
Q

How are K+ ions returned to interstitial space (proximal convoluted tubule)?

A

active transport into cell creates K+ concentration gradient, so they diffuse through K+ channels back into interstitial space

283
Q

How is Na+ moved from the tubule fluid into tubule cells in the ascending loop of Henle?

A

using a cotransporter, Na-K-Cl transporter (NKCC)

284
Q

How does Na-K-Cl transporter work?

A

Na+ is pumped into tubule cells through contransport with Cl- and K+

285
Q

How is K+ returned to the tubule fluid?

A

eventually K+ has a high concentration in the cell and diffuses back into tubule fluid -> this keeps the transporter moving

286
Q

How does Na+ move from tubule cells to interstitial fluid in the ascending loop of Henle?

A

Na+/K+ ATPase

287
Q

How does Na+ move from the tubule fluid into the tubule cells in the collecting ducts?

A

diffusion

288
Q

How does Na+ move from the tubule cells to the interstitial space in the collecting ducts?

A

Na+K+ ATPase moves Na+ into interstitial space and K+ back into cells

289
Q

What is the hormone that controls rebabsorption of Na+?

A

aldosterone

290
Q

What type of hormone is aldosterone?

A

a steroid hormone

291
Q

How does aldosterone work?

A

it changes the number of ion channels and Na+K+ ATPase transporters to change how much salt is moved across

292
Q

How long does aldosterone take to work?

A

hours as it is a steroid hormone

293
Q

Where does water reabsorption occur?

A

DESCENDING loop of Henle and the collecting ducts

294
Q

How does water move into the interstitial space in the descending loop of Henle?

A
  1. the descending loop is permeable to water, so it can freely move into the interstitial space
  2. reabsorbtion of salt occurs at the ascending loop, so creates a hypertonic solution (high salt concentration) in the interstitial fluid surrounding the loop of Henle
  3. this causes water to diffuse out of the descending loop of Henle by osmosis
295
Q

How does countercurrent flow work in the loop of Henle?

A
  1. blood flow around the loop of Henle is counter to flow through the loop of Henle
  2. the freshly filtered blood (low in salt) goes next to ascending LOH first, encouraging salt reabsorption
  3. the salt-rich blood circulates around descending loop
  4. so water is reabsorbed into the blood
  5. maintains concentration gradient
296
Q

How is water absorbed into the collecting ducts?

A

diffusion through aquaporins as the interstitial space will be full of salt from Na+ reabsorption

297
Q

Which hormone controls water re-absorption?

A

vasopressin

298
Q

What type of hormone is vasopressin?

A

a protein that acts on g protein-coupled receptord

299
Q

How does vasopressin work?

A

causes vesicles with aquaporins to fuse with plasma membrane of tubule cells, increasing water reabsorption

300
Q

Why is the action of vasopressing much quicker than aldosterone?

A

vasopressin has aquaporins already made in vesicles, aldosterone involves making more transporters

Pharmacy (6 decks)

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