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PHA333 > Topical preparations (Dodu) > Flashcards

Topical preparations (Dodu) Flashcards

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
Q

2 excipients for ointments

A

antioxidants

antimicrobial preservatives

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26
Q

What do antioxidants do?

A

prevent oxidation of the oily base

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27
Q

examples of antioxidants

A

butylated hydroxyanisole (BHA)

butylated hydroxytoluene (BHT)

propyl gallate (higher concs, safer)

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28
Q

When to use antimicrobial preservatives?

A

water miscible/soluble bases

-> likely to absorb moisture, to prevent microbial growth

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29
Q

examples of antimicrobial preservatives

A

benzoic acid

cationic surfactants - cetrimide

sorbic acid

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30
Q

What must excipients be for using in an ointment?

A

compatible with drug and base

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31
Q

manufacturing process of ointments

A

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

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32
Q

en is melting/mixing process appropriate for oinement manufacture

A 
HP
macrogols of high MW
wool fat
beeswax
cetostearyl alcohol
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33
Q

When are solids that are soluble/dispersible in molten base added in oinmnent manufacture?

A

added as fine powder during cooling

34
Q

When are liquids/semisolid ingredients added in oinmnent manufacture?

A

during cooling at around 40 deg C

35
Q

When are volatine/heat sensitive ingredients added in oinmnent manufacture?

A

added into cooled base

36
Q

When are solids that are insoluble solids added in oinmnent manufacture?

A

added as fine (180um seive) or very fine (125um seive) powder into cooled base by trituration

37
Q

What is trituration? (levigation method)

A
  • 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
Q

types of mixers for ointments

A
  • 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
Q

minotoring parameters for ointment manufacture

A

temperature

paddle/scraper speed

40
Q

critical manufacturing parameters for ointments

A
  • 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
Q

stirring during ointment manufacture

A
  • 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
Q

cooling rate during manufacture of ointments

A

gradual cooling to avoid granular appearance

43
Q

final appearance for manufacture of ointments

A
  • smooth, shiny, semisolid product

- adequate viscosity to prevent solid particle sedimentation

44
Q

What is a cream?

A

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
Q

3 types of creams

A
  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
Q

o/w cream

A

vanishing cream
washable
cooling action
classified according to surfactant used (non-ionic, cationic, anionic)

47
Q

w/o creams

A

oily
emolient and cleansing action
less greasy than ointments
contain lipophilic emulsifying agents - wool alcohols

48
Q

formulation of aqueous cream - light emollient

A

emulsifying ointment 30%
phenoxyethanol 1% (preservative)
water

anionic

49
Q

formulation of oily cream - Hydrous ointment

A

wool alcohols ointment 50% w/w
phenoxyethanol 1% (preservative)
dried magnesium sulphate 0.5%
water up to 100%

50
Q

What does the type of cream depend on?

A

relative amount of the 2 phases

type of surfactant added

51
Q

How to prevent microbial growth in aqueous phase of cream formulation?

A
  • manufacture under aspetic conditions

- antimicrobial preservatives

52
Q

examples of antimicrobial preservatives

A 
phenoxyethanol
parabens
chlorocresol
benzoic acid
cetrimide
53
Q

What do antioxidants do in cream formulations?

A

prevent oxidation of oily phase

54
Q

method used for cream formulation

A

fusion method

55
Q

fusion method for cream formulation

A
  • 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
Q

When are heat sensitive ingredients added in cream manufacture?

A

added to cold semi-solid mixture by trituration

57
Q

3 parts of the manufacturing equipment for cream manufacture

A

anchor/propeller stirrer

shear mixers

homogeniser

58
Q

What does anchor/propeller stirrer do (cream manufacture)?

A

initial stirring of individual phases

59
Q

What does shear mixer do (cream manufacture)?

A

emulsification process
semisolid materials don’t flow easily
high degree of shear mixing required

  • planetary mixers
  • sigma blade mixers
60
Q

What does homogeniser do (cream manufacture)?

A

globule size recuction of emulsified mixture

inc stability of emulsified semisolid product

61
Q

adv/disadv with anchor and propeller stirrer (low shear stirrers)

A
  • 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
Q

What mixer is used for the 2 phases together?

A

planetary mixer

63
Q

How do planetary mixers work?

A
  • 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
Q

What does homogeniser do?

A

gives a fine dispersion with a uniform size distribution

-> big globules, uneven size go in, small globules, same size come out

65
Q

What are gels?

A

liquids gelled by means of suitable agents

semisolid preparations containing

  • continuous liquid phase (solvent)
  • thickening/gelling agent
66
Q

2 phases of gels

A
  1. liquid phase

2. thickening (gelling) agent

67
Q

liquid phase of gels

A

polar solvent

  • water, alcohol, glycerol
  • aqueous gels of hydrogels

non-polar solvent

  • liquid paraffin, vegatable oils
  • oily gels or lipogels
68
Q

thickening (gelling) agent of gels

A

provides semi-solid consistency

influences the gel viscosity and the drug release properties

69
Q

2 types of gels

A

hydrogels

lipogels

70
Q

hydrogels

A

aqueous continuous phase

natural polymers - pectin, tragacanth, sodium alginate, carageenan, gelatin

synthetic polymers - HPMC, carbomers, poloxamers

71
Q

lipogels

A

oil as the continuous phase

colloidal silica
aluminium
magnesium stearate
clays

72
Q

examples of hydrogels

A

benzoyl peroxide gel

isotretinoin gel

73
Q

What does manufacture of gels depend on?

A

properties of gelling agent

74
Q

manufacture of gels using carbomer powder

A
  • 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
Q

manufacture of gels using gelatin powder

A
  • dissolve in hot water
  • reduce temp and causes gel formation

** NEED TO CHANGE THE TEMP - DECREASE

76
Q

manufacture of gels using poloxamer

A
  • dissolve in cold water
  • '’cold method’’
  • gradually inc temp and it changes from solution to gel

**INC TEMP

77
Q

additives in gel manufacture

A

humectants - propylene glycol, prevenet drying of gel

preservatives - must be compatible with gelling agent

antioxidants

78
Q

QC for topical preparations

A
  • test for deliverable weight (mass) or volume of semi-solid preparations
  • consistency by penetrometry
  • preservative peoperties
  • drug release properties
79
Q

QC - preservative properties

A

efficacy of antimicrobial preservation

microbiological quality of pharmaceutical preparations

methods of preparation of sterile products

80
Q

QC - drug release properties

A

Franz cells

imaging techniques

PHA333 (27 decks)

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