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the medicine Flashcards

1
Q

List three types of emulsifying agent

A

surfactant
Hydrophilic colloids
Finally, divided solid particles

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2
Q

List three factors, which influence emulsion viscosity

A

Oil to water ratio
Globule size
emulsifier used

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3
Q

List two examples of factors which can cause chemical instability

A

change in pH
Electrolytes

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4
Q

what factors should be considered when choosing a preservative for an emulsion

A

Its concentration in aqueous phase, which is related to its partition coefficient

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5
Q

what is the definition of a stable emulsion

A

One of which the dispersed globules retain their initial character, and remain uniformly distributed throughout the continuous phase

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6
Q

give 4 methods of stability testing

A

microscopic examination
Global size analysis
Viscosity changes
Accelerated stability testing

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7
Q

What is macroscopic examination?

A

Measure the degree of creaming or sedimentation occurring over time

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8
Q

What is globule size analysis?

A

If global size increases a number of globules decrease. Coalescence is occurring. This will cause an increased rate of creaming/sedimentation.

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9
Q

What is viscosity changes?

A

any change in globule size, number or position may be detected by a change in viscosity

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10
Q

What is accelerated stability testing?

A

centrifugation
Storage at adverse temperatures

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11
Q

experimental determination of the optimum HLB

A

using 2 surfactants, prepare a series of emulsions, with varying HLB values

The system with minimum creaming or separation of phases has the optimum HLB

And measure the mean, globule size using laser, diffraction methods

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12
Q

What does an increase in temperature: decrease apparent viscosity of continuous phase lead to

A

increased creaming

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13
Q

temperature increase: increase kinetic motion of dispersed, droplets, more globules, Collide leads to

A

Increased creaming

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14
Q

Temperature increased: increasing kinetic motion of emulsifying agent at interface. This can weaken the film leading to.

A

Coalescence

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15
Q

freezing, an oil and water emulsion leads to ice, and crystals, forming in the aqueous phase. This leads to

A

exerting, unusual pressures on the adsorbed emulsifier film

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16
Q

freezing and oil in water emulsion. The dissolved electrolyte may concentrate in the unfrozen water. This may lead to

A

Affecting the film charge density

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17
Q

What may not give the same degree of stability at the required HLB

A

not all emulsion combinations

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18
Q

mineral oil emulsions have been used to treat constipation

However, the use has been discouraged, because

A

The emulsion may reduce absorption of oil, soluble vitamins

Very small mineral oil globules may be absorbed into the bloodstream

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19
Q

emulsion drug delivery: GIT absorption

A

A drug most dissolve in the aqueous fluid of the GIT prior to absorption

But the drug must still be sufficiently lipophilic to allow partitioning across the lipid membrane of the cells

If delivered in an oil, the drug can be absorbed by the same route as an ingested fat

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20
Q

what are micro emulsions

A

globule size of 5-140nm
The form spontaneously when components are mixed at the appropriate ratio

These are thermodynamically stable

They employ a high concentration of surfactant

They are often called swollen micelles

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21
Q

give an example of a micro emulsion

A

sandimmune neoral

commercially available from novartis

It’s gives a higher rate of absorption
A shorter residence time

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22
Q

what is a self emulsifying system

A

these are mixtures of oil and surfactant that form emulsions on mixing with water with little or no energy input

They can form spontaneously, on addition of one phase to the other

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23
Q

What is the parenteral route?

A

injectable formulation of lipophilic drugs

Parenteral nutrition: provides nutrition, especially calories by parenteral route

fat emulsions O/W with mean globule size of 200-300nm

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24
Q

Tell me about parenteral nutrition

A

patients who must be fed parenterally over a longer period of time need amino acids, electrolytes, trace, elements, and vitamins, as well as calories.

All in one products are available

Due to numerous components, there is often unexpected interactions

Often supplied as a multi bag system

Before application, the components are mixed and extra vitamins and trace, elements can be given

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25
what does this recommendation mean? Additives may only be added to fat emulsions when compatibility is known
IV fat emulsions may break down with coalescence of fat globules and may separate with addition of antibiotics for electrolytes. Therefore, there is an increased risk of emobolism
26
what is intralipid as an IV drug carrier
lipophilic drugs can be dissolved in the soya bean oil This is an alternative to solubilising the drug in cremophor EL examples include: diazepam and propofol
27
Describe an accelerated stability test you could employ to check for creaming
centrifugation or Increasing temperature
28
describe two advantages of micro emulsions
increased stability Can provide an increased bioavailability
29
skin overall
it is the largest organn Containment of fluids and tissues Regulate heat and water loss Acts as a barrier to chemicals and micro organisms Consists of three functional layers
30
what is the hypodermis
subcutaneous, fat, layer It is relatively thick Insulates the body Protects against shock energy source Contains blood vessels and nerves
31
what is the dermis
major component of human skin 3-5 mm thick support and elasticity Extensive vasculature Regulates temperature Delivers oxygen and nutrients Removes toxins and waste
32
what are the epidermis layers?
The outermost layers 0.1-0.2mm thick Provides protection Cell renewal (lifetime is four weeks) avascular Stratum corneum forms the rate controlling barrier
33
What is the stratum corneum?
formed like bricks and mortar Dead, flattened keratin rich cells (corneocyte) Intracellular lipids (bilayer arrays)
34
What is the main barrier to drug absorption across the skin?
Stratum corneum
35
What are the three main layers of the skin?
Hypodermis Dermis Epidermis
36
What are advantages of transdermal drug delivery?
The avoidance of a significant presystemic metabolism (gastrointestinal tract, or by the liver) Lower daily dose You can avoid multi dozing Extend the duration of drug action, reduces frequency of dozing Improve patient, compliance and acceptability Simple removal of dose
37
What are disadvantages of transdermal drug delivery?
skins barrier function limits the drug absorption not all drugs are candidates Variation in permeation rate Race, age, environmental history Irritation and sensitisation at the site of administration or application
38
Target to regions: surface
to generate a protective layer or attacking bacteria/fungi Protective films or sunscreens to hinder moisture loss Topical antibiotics, antiseptic’s and deodorant to kill surface micro organisms
39
Target regions: stratum, corneum
how to improve emollience by raising water content Creams and ointments to enhance the moisture Stimulate sloughing (removal of dead cells) Salicylic acid Ideally, should not enter viable tissue
40
Target regions: viable, epidermis, and the dermis
can treat many diseases provided the drugs can be delivered to the receptors efficiently Steroids and non-steroidal anti-inflammatory agents Anaesthetic drugs to reduce pain Antihistamines to alleviate itch
41
Target regions: skin appendages hair, follicles and sweat glands
known as a shunt route(by passes stratum, corneum) High permeability Low surface area Antiperspirant to reduce hyperhidrosis of sweat glands Barium sulphite as dipilarories
42
Target regions: systemic
can treat several conditions Travel sickness (hyoscine) Hypertension (clonidine) Smoking (nicotine) Pain (Fentanyl) Limited due to low delivery efficiency
43
what are routes of absorption?
mostly via transepidermal Need to circumvent the stratum corneum
44
Transepidermal route: transcellular route
though horny cells
45
trans epidermal route: intracellular route
avoids horny cells through lipid matrix instead Predominant, diffusional path
46
What are optical drug characteristics?
small molecular weight Lipophilic Low, melting point (good solubility properties) Hydrogen bonds (interaction with pull ahead, groups of lipids in the skin/reaches plateau) pKa (unionised fraction).
47
what is flux
The rate of diffusion across a permeable membrane
48
what is the octagonal water partition coefficient
LogP(Octanol/water) > 3 is highly lipophilic LogP(Octanol/water) 1-3 is intermediate LogP(Octanol/water) <1 is hydrophillic
49
When do you get the best absorption?
from small and lipophillic molecules
50
What is the pH partition hypotheses?
many drugs are weak acids or bases un ionised molecules partition into lipid membranes ionised ones do not Transdermal absorption of weak electrolyte is favoured by the unionised form
51
what are the two routes of absorption through skin?
Transcellular Paracellular (main route)
52
What are the optimal drug characteristics for transdermal delivery?
small molecular weight Lipophilic Hydrogen bond formation Low, melting point unionised
53
Give examples of dermatological formulations
liquid preparations gels Powder ointments Creams (O/W W/O) Pastes
54
what are creams
O/W or W/O emulsions for topical administration
55
creams O/W properties
less greasy feel and a more pleasant to use Easy rinsing from the skin Variations, in consistency form fluid lotions to viscous creams popularity with patients prone to microbial contamination As the continuous phase evaporates, concentration of water, soluble, drug increases, promoting absorption non occlusive It deposit slip it, and other moisturises on the skin, resulting in the skins hydration Requires mixed emulsifiers (surfactant and fatty acids)
56
creams W/O properties
emollient cleansing agents use w/o emulsifying agents
57
what is an ointment
A greasy semisolid a system that is applied externally (skin and mucosal membrane) Formulation involves dispersion or dissolution of a medicament into an ointment base Physio chemical properties of the drug and ointment base are so crucial
58
what are choices of ointment base
dependent on several factors: Site of application , occlusion Rate of drug release: solubility and diffusion of drug Drug stability: hydrolysis is reduced in the hydrophobic base rheology: effect of drug inclusion
59
what are hydrocarbons bases?
hard, soft, liquid paraffin Properties: They form, thick, occlusive films Sticky feel Difficult to remove from skin Variation inconsistency with temperature change Tend to be poor solvents
60
What are silicones?
have similar properties to hydrocarbons Dimethicone Water repellent with low surface tension Barrier creams to protect against water, soluble irritants Nappy rash, bedsore, inconsistence
61
What are absorption bases?
less occlusive than hydrocarbons Non-emulsified Absorb water to form W/O emulsions Inclusion of low, HLB surfactants (W/O emulsifying agent) W/O emulsions
62
What are emulsifying bases
anhydrous bases containing O/W emulsifying agent (HLB values of 9-11) so they are water, miscible, washable, or self emulsify Emulsifying ointment
63
What are water soluble bases?
mixtures of high and low molecular weight polyethylene glycols They have an ointment like consistency, non greasy Soften and melt onto the skin Unable to incorporate large volumes of aqueous solutions Reduce the antimicrobial activity of quaternary, ammonium, compounds.
64
What is a paste?
up to 50% of the powder is dispersed in an ointment base can localise the action of an irritant or staining materials forms and opaque film (sunblock)
65
what is a gel
semisolid systems, in which there is an interaction between colloidal particles with a liquid vehicle Can be based on: type 1: dispersed, solids (network of flocculation) type 2: hydrophilic, polymers
66
what are type 1 gels
hydrogels Covalent interactions mediated by cross-linkers Don’t flow when stress is applied Able to absorb a considerable mass of water Used as a wound dressings and sustained release implants
67
what are type 2 gels
most common Have a weak bonds (Vander walls, ironic, hydrogen bonding) Application of stress leads to temporary reversible destruction of interactions pseudoplastics
68
Why is formulation choice important?
liquid: rapid, short term, input of permeant Semisolid: increased resistance Patches: extended drug delivery
69
why would you expect creams or ointments to have a longer shelf life and why?
ointments – lack of water phase; generally improve physical, chemical, and microbial stability
70
The choice of ointment base depends on:
site of application Drug, release and stability rheology
71
What is permeability enhancement?
It is the improvement or increase in the permeability of a material or substance.
72
What are some materials that increased permeability enhancement?
permeability, enhancing excipients Supersaturation Liposomes Microemulsions Lipid nano particles Generally localised effect in the stratum corneum Prodrugs
73
What is physical permeation enhancement?
Needles? Obvious and most straightforward method Long history of use Disadvantages: Pain Psychological Infection risk
74
What are minimally invasive methodologies?
tape stripping suction ablation iontophoresis Electroporation Sonophoresis High velocity particles Laser assisted delivery Micro needles
75
What is tape stripping?
simply remove barrier An adhesive tape removes sequential layers of the stratum corneum Hydration (occlusion) helps Cumbersome and uncontrolled
76
what is suction ablation
removal of the stratum corneum by suction blister formation Application of vacuum to select an area Create a portal for drug delivery at stratum lucidum Pain-free?
77
what is iontopheresis
transfer of charged substances under the influence of an electric field Enlarges range of drug candidates, particularly Polar and or charged particles Acts on molecules themselves
78
what is electroporation
A large voltage treatment over a short period of time Producers transient hydrophilic pores Universal physical phenomenon of lipid bilayers
79
what is sonopheresis/phonophoresis
It’s uses ultrasonic energy Formation and subsequent collapse of gas bubbles (cavitation) Temperature elevation
80
What are high velocity particles
compressed gas blast fine particles through the skin Useful for larger, macromolecules (vaccines) Drug may be coated on particles Pain-free, but worry free?
81
What is Laser assisted delivery?
there are two processes: ablative: high energy forms pores optoacoustic: stress wave transiently increases permeability Hydrophilic and lipophilic drugs Well controlled
82
What are micro needles?
they pierce the upper epidermis They do not reach nerve receptors They can be solid or hollow They are generally silicone They are fabricated by wet etching Nanovic technology coated microneedle – usually stainless steel arrays coated with a formulation containing drug Polymeric, micro needles – higher resilience, can provide improved, drug release pattern because of the polymers degradation and dissolving capabilities

week 21 (3 decks)

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