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Topical preparations (Dodu) Flashcards

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1
Q

What is a topical preparation?

A

semi-solid preparations for cutaneous application are intended for local/transdermal delivery of active substances or for their emollient/protective action

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2
Q

examples of semi-solid preparations for application onto the skin

A

ointments
pastes
creams
gels

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3
Q

characteristics of topical preparations

A

visco-elastic pharmaceutical preparations

non-Newtonian rheological behaviour

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4
Q

What are the 2 phase systems of topical preparations?

A

single phase system
- ointments, pastes, gels

two phase systems (2 immicible phases, oil and water)
- creams

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5
Q

multiple functions of skin

A

physical and chemical barrier

regulation of body temperature - maintains homeostasis

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6
Q

composition of skin

A

epidermis
dermis (capillaries, nerves)
subcutaneous tissue

hair follicles, sweat ducts, sebaceous glands (in dermis)

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7
Q

thickness range of epidermis

A

0.06 - 0.8 mm

thin on eyelids
thick on soles of feet

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8
Q

outer layer of epidermis

A

stratum corneum

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9
Q

stratum corneum structure

A

highly lipophilic
made of keratinocytes (skin cells)
main barrier to drug penetration

dry - 10um
hydrated - 50um

dry composition - 75-85% proteins, lipid 15%, water

lipids - ceramides (only found in skin), FAs, cholesterol

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10
Q

structure of dermis

A

connective tissue
- aqueous layer
collagen, 4% elastin
3-5mm thick

visible layer

  • blood vessels, nerves, lymphatics, skin appendages
  • delivers nutrients to skin
  • removes waste products
  • enzymes (esterases)
  • skin colour (melanocytes)

acts as sink for diffusing drug molecules - conc gradient for passive diffusion

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11
Q

structure of subcutaneous layer

A 
fat
thickness varies
- age
- endocrine
- nutritional status
- body site

protection

  • thermal insulation
  • mechanical cushioning
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12
Q

2 effects a topical dosage form has

A
  1. topical effect - drug goes into skin for local action

2. systemic effect - drug diffuses into deeper skin layers and is removed by the dermal capillaries

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13
Q

What is an ointment?

A

single phase basis (vehicle) in which solids or liquids may be dispersed

contains dissolved or suspended drug in the vehicle

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14
Q

How are ointments classified?

A

according to type of base

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15
Q

ideal properties of base

A
  • non irritant
  • non sensitising
  • not retard wound healing
  • inert, physically/chemically stable
  • smooth
  • odourless
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16
Q

4 types of ointment bases

A
  1. hydrocarbon bases (fatty)
  2. absorption bases
  3. emulsifying bases
  4. water soluble bases
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17
Q

examples of hydrocarbon bases

A

paraffins
vegetable oils
animal fats/waxes
silicones

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18
Q

examples of absorption bases

A

wool alcohols (lanolin alcohols) -> woll fat + 30% cholesterol

hydrous wool fat (hydrous lanolin) -> wool fat + 25-30% purified water

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19
Q

examples of emulsifying bases

A

emulsifying wax 30% + WSP + LP (liquid paraffin)

emulsifying wax = cetostearyl alcohol + surfactant

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20
Q

examples of water soluble bases

A

macrogols (PEGs)

  • vary in consistence depending on average Mr
  • Mr 200-700 viscous liquids (hygroscopic)
  • Mr >1000 waxy solid
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21
Q

formulation of Dithranol ointment - psoriasis

A

dithranol (fine powder) 0.1-2% w/w
YSP

  • SP replaced with HP to make stiffer consistency
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22
Q

formulation of Calamine ointment - antipruritic

A

Calamine 15% w/w

WSP

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23
Q

formulation of hydrocortisone ointment - mild eczema, allergic contact dermatitis, insect bites

A

micronised drug (0.5-1% w/w)

wool fat

WSP

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24
Q

formulation of simple ointment

A

wool fat 5%
cetostearyl alcohol 5%
HP 5%
WSP 85%

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25
2 excipients for ointments
antioxidants antimicrobial preservatives
26
What do antioxidants do?
prevent oxidation of the oily base
27
examples of antioxidants
butylated hydroxyanisole (BHA) butylated hydroxytoluene (BHT) propyl gallate (higher concs, safer)
28
When to use antimicrobial preservatives?
water miscible/soluble bases -> likely to absorb moisture, to prevent microbial growth
29
examples of antimicrobial preservatives
benzoic acid cationic surfactants - cetrimide sorbic acid
30
What must excipients be for using in an ointment?
compatible with drug and base
31
manufacturing process of ointments
fusion (melting) followed by constant stirring during cooling solid bases and ingredients that can be melted are combined and are melted together, max 70 deg C waxy solids are grated, weighed and added first
32
en is melting/mixing process appropriate for oinement manufacture
``` HP macrogols of high MW wool fat beeswax cetostearyl alcohol ```
33
When are solids that are soluble/dispersible in molten base added in oinmnent manufacture?
added as fine powder during cooling
34
When are liquids/semisolid ingredients added in oinmnent manufacture?
during cooling at around 40 deg C
35
When are volatine/heat sensitive ingredients added in oinmnent manufacture?
added into cooled base
36
When are solids that are insoluble solids added in oinmnent manufacture?
added as fine (180um seive) or very fine (125um seive) powder into cooled base by trituration
37
What is trituration? (levigation method)
- method of incorporating insoluble solids or small amounts of liquids into the base - solid should be in fine powder - conc mixture of insoluble component in base followed by gradual dilution (doubling) with the rest of the base - flat based mortar with flat-head pestle required for large scale batch production
38
types of mixers for ointments
- stationary mixing tank with heating system - stainless steel or porcelain (porcelain not practical, doesn't clean easily, not good heat conductor) - rotating paddle or anchor for stirring - scraper for easy product removal from mixing tank - > Hobart mixer
39
minotoring parameters for ointment manufacture
temperature paddle/scraper speed
40
critical manufacturing parameters for ointments
- melting temperature (of solid bases) - degradation temperature of any heat sensitive component - solubility of ingredients in base - particle size reduction of insoluble solids - stirring - cooling rate - final appearance
41
stirring during ointment manufacture
- throughout mixture to ensure homogenity - gentle stirring to avoid incorporation of air (air bubbles) - constant stirring until mixture has cooled to avoid lump formation
42
cooling rate during manufacture of ointments
gradual cooling to avoid granular appearance
43
final appearance for manufacture of ointments
- smooth, shiny, semisolid product | - adequate viscosity to prevent solid particle sedimentation
44
What is a cream?
multiphase preparation consisting of a lipophilic phase and an aqueous phase semi-solid emulsion for external application 2 immicible liquid phases (oily and aqueous) with emulsifying agent
45
3 types of creams
1. semi solid emulsion for external applicaiton (2 immicible liquid phases (oil and aqueous), emulsifying agent) 2. o/w vanishing cream 3. w/o oily cream
46
o/w cream
vanishing cream washable cooling action classified according to surfactant used (non-ionic, cationic, anionic)
47
w/o creams
oily emolient and cleansing action less greasy than ointments contain lipophilic emulsifying agents - wool alcohols
48
formulation of aqueous cream - light emollient
emulsifying ointment 30% phenoxyethanol 1% (preservative) water anionic
49
formulation of oily cream - Hydrous ointment
wool alcohols ointment 50% w/w phenoxyethanol 1% (preservative) dried magnesium sulphate 0.5% water up to 100%
50
What does the type of cream depend on?
relative amount of the 2 phases type of surfactant added
51
How to prevent microbial growth in aqueous phase of cream formulation?
- manufacture under aspetic conditions | - antimicrobial preservatives
52
examples of antimicrobial preservatives
``` phenoxyethanol parabens chlorocresol benzoic acid cetrimide ```
53
What do antioxidants do in cream formulations?
prevent oxidation of oily phase
54
method used for cream formulation
fusion method
55
fusion method for cream formulation
- aqueous phase and water sol ingredients mixed together and heated - oily phase and oil sol ingredients mixed together and heated - > heat separately first - heating temp muct be the same for both phases - mixing of the 2 phases - emulsification - > usually disperse phase into continuous phase - > o/w creams prepared using phase inversion technique where aw phase added into oily, followed by gradual phase inversion - gradual cooling and constant stirring - homogenisation for globule size reduction
56
When are heat sensitive ingredients added in cream manufacture?
added to cold semi-solid mixture by trituration
57
3 parts of the manufacturing equipment for cream manufacture
anchor/propeller stirrer shear mixers homogeniser
58
What does anchor/propeller stirrer do (cream manufacture)?
initial stirring of individual phases
59
What does shear mixer do (cream manufacture)?
emulsification process semisolid materials don't flow easily high degree of shear mixing required - planetary mixers - sigma blade mixers
60
What does homogeniser do (cream manufacture)?
globule size recuction of emulsified mixture inc stability of emulsified semisolid product
61
adv/disadv with anchor and propeller stirrer (low shear stirrers)
- suitable for low/medium viscosity materials but not for highly viscous/sticky materials (phases together/semi-solid mix) - > when aqueous and oily phase are separate - can leave dead spots in mixture
62
What mixer is used for the 2 phases together?
planetary mixer
63
How do planetary mixers work?
- rotate and travel through the container - pass through every point in the batch, not just along the periphery - mixing blade spins around its own axis and simultaneously rotates around the whole container -> suitable for high viscosity
64
What does homogeniser do?
gives a fine dispersion with a uniform size distribution -> big globules, uneven size go in, small globules, same size come out
65
What are gels?
liquids gelled by means of suitable agents semisolid preparations containing - continuous liquid phase (solvent) - thickening/gelling agent
66
2 phases of gels
1. liquid phase | 2. thickening (gelling) agent
67
liquid phase of gels
polar solvent - water, alcohol, glycerol - aqueous gels of hydrogels non-polar solvent - liquid paraffin, vegatable oils - oily gels or lipogels
68
thickening (gelling) agent of gels
provides semi-solid consistency influences the gel viscosity and the drug release properties
69
2 types of gels
hydrogels lipogels
70
hydrogels
aqueous continuous phase natural polymers - pectin, tragacanth, sodium alginate, carageenan, gelatin synthetic polymers - HPMC, carbomers, poloxamers
71
lipogels
oil as the continuous phase colloidal silica aluminium magnesium stearate clays
72
examples of hydrogels
benzoyl peroxide gel isotretinoin gel
73
What does manufacture of gels depend on?
properties of gelling agent
74
manufacture of gels using carbomer powder
- disperse in vigorously stirred water - neutralise with addition of base (inc pH to 6-11) - > acidic functional group of carbomer ionises, solubilises - slow aggitation with paddle stirrer - > neutralised aqueous gel ** NEED TO CHANGE THE pH TO ALLOW CONVERSION OF SOLUTION TO GEL (DISSOLUTION OF CARBOMER INTO WATER)
75
manufacture of gels using gelatin powder
- dissolve in hot water - reduce temp and causes gel formation ** NEED TO CHANGE THE TEMP - DECREASE
76
manufacture of gels using poloxamer
- dissolve in cold water - ''cold method'' - gradually inc temp and it changes from solution to gel **INC TEMP
77
additives in gel manufacture
humectants - propylene glycol, prevenet drying of gel preservatives - must be compatible with gelling agent antioxidants
78
QC for topical preparations
- test for deliverable weight (mass) or volume of semi-solid preparations - consistency by penetrometry - preservative peoperties - drug release properties
79
QC - preservative properties
efficacy of antimicrobial preservation microbiological quality of pharmaceutical preparations methods of preparation of sterile products
80
QC - drug release properties
Franz cells imaging techniques

PHA333 (27 decks)

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