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Formulation And Technology > Ointment And Gel > Flashcards

Ointment And Gel Flashcards

1
Q

Classification of ointment base

A

Two ways of classifying

1) composition of base
- oleaginous base
- absorption base
- emulsion base
- water soluble base.

2) degree of penetration of ointment upon application to skin
- Epidermatic Little power of penetration E.g. oleaginous bases (Hydrocarbon)
- Endodermatic Some power of penetration E.g. oleaginous base (Vegetable oil), absorption bases
- Diadermatic Deep penetration promoting systemic drug absorption E.g. emulsion bases, PEG bases

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2
Q

What is an oleaginous bases

A

Composed of entirely lipophilic materials

may consist of more than one such substances.

Example
Hydrocarbon
eg petrolatum, paraffin wax, liquid paraffin, microcrystalline wax, ceresin, plastibase
Vegetable oils
eg peanut oil, almond oil, sesame oil, olive oil, coconut oil,
Hydrogenated and sulfated oils
eg hydrogenated cotton seed, soya bean, corn and castor oils
Fatty Acids, alcohols and esters
eg stearic acid, oleic acid, palmitic acid, myristic acid, lauric acid, stearyl alcohol, cetyl alcohol, oleyl alcohol, lauryl alcohol, myristyl alcohol, glyceryl tristearate, isopropyl myristate, ethylene glycol dilaurate/distearate
Silicones
eg dimethylpolysiloxanes methylphenylpolysiloxanes stearyl esters of dimethylpolysiloxanes

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3
Q

What is petrolatum

A

A type of Hydrocarbon (oleaginous base)

Tasteless,odourless,greasy Melting point:38-60C Excellent emollient Compatible with many drugs
Provides optimal drug stability

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4
Q

Properties of oleaginous base

A
  • Anhydrous
  • non hydrophilic
  • non-water removable
  • greasy
  • occlusive
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5
Q

Advantage of using oleaginous base

A

1) it can be used to incorporate active ingredients that are prone to hydrolysis.

2) it can be used to hold volatile ingredients (cannot use hydrophilic base)
eg tiger balm

3) Ideal formulation for eyes, piles (hemorrhoid; at rectal)
coz wont be wash off easily by water.

4) Prevent lost of water from skin by forming a layer.
5) good for dry skin and prevent dry skin.

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6
Q

Disadvantage of oleaginous bases

A

Hard to wash off with water–> use soap

not for hairy places like hair.

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7
Q

What is absorption base

A

A type of ointment base
which has the ability of absorbing considerable quantities of water (30%) and still retaining their ointment-like consistency (consistency wont decrease)

They do not contain water as a component in their basic formula. Generally composed of oleaginous base incorporated with hydrophilic substance(s), such as cholesterol, wool fat, lanolin alcohols and surfactants.

Hydrophilic substances gives the ability for AB to absorb water.

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8
Q

Absorption bases provide _____

A

provide some occlusion of the skin, hydrate the strateum corneum and can be left in contact with the tissue for prolonged periods of time.

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9
Q

Wool fat is???

A

A type of absorption base.

Anhydrous lanolin Complex mixture including cholesterol, lanolin alcohols and lanolin esters A natural absorption base Problem with allergy

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10
Q

Break down the formulation

Simple Ointment BP
Wool fat 50g
Hard paraffin 50g Cetostearyl alcohol 50g White/Yellow soft paraffin 850g

A

wool fat
- Absorption base
making this formulation more hydrophilic

the rest are oleaginous bases.

Hard paraffin and cetostearyl alcohol are waxy material that helps to increase consistency ,

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11
Q

break down Hydrophilic Petrolatum USP

Cholesterol 3%
Stearyl alcohol 3%
White wax 8%
White petrolatum 86%

A

Cholesterol is absorption base

stearyl alcohol and wax are to increase consistency

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12
Q

Properties of absorption bases

A 
anhydrous
absorb water
insoluble in water
greasy
occlusive
  • open container can absorb water
  • not good for Abx that is prone to hydrolysis

Occlusive therefore good emollient.

suitable for incorporation of hydrophilic (aq) solution of drug

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13
Q

What is emulsion base

A

These are semi-solid emulsions or creams

Composed of one liquid dispersed in another immiscible liquid with the aid of emulgent(s)

forming
water-in-oil emulsion bases
oil-in-water emulsion bases

Small amounts of water can be incorporated into the base without decreasing the consistency of the base markedly

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14
Q

Emulsion bases solid or liquid etc

A

liquid at higher temp

when cooled = semi-solid

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15
Q

Types of emulsion bases

A

vanishing cream and cold cream

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16
Q

What is vanishing cream

A

form from emulsion base

Contain:
1)Large proportion of water (as high as 80%)

2)Stearic acid(~20%)
in situ soap, pearlescence

3) Humectant e.g. glycerin,
propylene glycol

Vanishing creams get absorbed easily and applied easily on skin

due to the presence of large amount of water it can form O/W emulsion too. thus when bottle is opened, water can be evaporated and water content inside will decrease, thus making spreading on skin difficult.
Thus humectant is needed to absorb water to prevent excess water loss

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17
Q

Function of stearic acid

A

Can be found in vanishing cream

  • to form in situ soap
  • pearlescence

Act as emulsifying agent to stabilize the cream.
Most stearic acid are not converted to soap. these are for pearlescence to make the cream more appealing.

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18
Q

Break down

Stearic acid 20% Potassium hydroxide 1.4%
Glycerin 10%
Water to 100%

A

Stearic acid reacts with potassium to form emulsifying agent and some extras are for pearlescene

Glycerin (humectant) is to prevent excess water loss

No oil presence and stearic acid is the only lipophilic compound.

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19
Q

Break down
Stearic acid 15%
White wax 2%
White vaseline 8% Triethanolamine 1.5% Propylene glycol 8% Water to 100%

A

Stearic acid reacts with triethanolamine to give triethanolamine stearic

propylene glycol acts as humectant

presence of white vaseline makes formula more greasy.

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20
Q

What is cold cream

A

A type of emulsion base
Contain less water (W/O emulsion) Leave behind a layer of oil/fat on skin to protect the skin

More occlusive than vanishing cream

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21
Q 
Break down 
Basic formula 
Beeswax 15% 
Liquid paraffin 50% Borax 1% 
Waterto100%
A

Beeswax and borax are emulgent

beeswax cause formulation to be semi-solid

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22
Q

Properties of emulsion base (O/W and W/O)

A

O/W type
Hydrophilic (miscible) Insoluble in water Water-removable Non-greasy
Poor emollient
Non-occlusive

W/O type
Hydrophobic (immisicible) 
Insoluble in water Non-Water-removable Greasy 
Good emollient (2nd to OB) 
Occlusive
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23
Q

What are water-soluble bases

A

These bases are soluble in water Examples:

  • Polyethylene glycol bases
  • Gels (can be taken orally)

PEG can be semi-solid or Solid (use as suppository)

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24
Q

What are PEG

A

Polyethylene glycols (PEGs) are also known as carbowaxes
General chemical formula: HOCH2(CH2OCH2)nCH2OH Non-volatile, water-soluble/miscible
Relatively inert and non-irritating to skin

Do not support mould growth

PEG <1000MW = liquid
PEG >1000MW = Solid or semi-solid

25
Q

properties of PEG base

A
  • Usually anhydrous
  • Hydrophilic
  • water soluble
  • water removable
  • non-greasy
  • Lipid-free
  • non-occlusive

if we add water then it can be hydrous but consistency will decrease so seldom done

NOT for drugs that are sensitive to hydrolysis

not good sites that is easily washed off

good for hairy region (wash off easily)

26
Q

What is gel

A

Gel is water soluble base

Semi-solids consisting of a solid component enclosing and interpenetrated by a liquid component

Solid component : large organic molecules or small inorganic particles
Liquid component: water or organic solvent

Topical gels may be prepared from various types of gelling agents
Depending on the gelling agent used, the gel may be single-phase or two-phase

27
Q

types of gelling agent

A

1) Natural gums
- tragacanth,carrageenan pectin, agar, alginic acid

2) Cellulose derivatives
- methyl cellulose (MC)
- carboxymethylcellulose (CMC)
- hydroxypropylmethyl cellulose (HPMC)
- hydroxyethyl cellulose (HEC)

3) Synthetic polymers
- carbopol

4) Clays
- Bentonite, veegum, laponite

28
Q

what is single phase gels

A

There are no apparent boundaries between the solid and liquid components

Solid component is lyophilic and disperses readily in the dispersion medium

Generally made up of large organic molecules
E.g. natural gums, cellulose derivatives and synthetic polymers

increase [macromolecules;gelling agent ] increases viscosity and thus become semi-solid
The macromolecules exist as “strands” in the gel

29
Q

Types of strand form in gel

A

depending on the gelling agent and dispersion medium

1) twisted matted fibres
2) partially bounded strands

1 –> form entangled network that increases viscosity

2 –> less permeable to drug due to the high crystalline region
–> sustained released of drug; drugs are released slowly

30
Q

why is gel rigid

A

The rigidity of the gel is attributed to the intertwining network which traps and holds the dispersion medium

Single-phase gels are generally stable on standing

A change in temperature or agitation may affect the physical state of the gel
ie changed from semi-solid to liquid

31
Q

What is two-phased gels

A

There are definite boundaries between the solid and liquid components

Solid component is lyophobic and does not disperse readily in the dispersion medium

Generally made up of small inorganic particles E.g. clays

increase [particles] has little effect on viscosity

These particles exist as floccules in the gel

Two-phase gelsare generally less stable

32
Q

properties of gel

A

Sol-Gel transformation
-Induced by temperature = thermal gels (eg methycellulose)
- increase in temperature = increase in rigidity
- drop in temperature = liquid
(so must use cold water to prepare gel)

but in general increase in temperature will changed from semi-solid to liquid.

  • Induced by shear stress = thixotropic gels (eg bentonite)
  • such gel need to achieve yield value to achieve sol-gel transformation.

Ability to absorb water with significant or insignificant increase in volume
- Swelling vs Imbibition

Syneresis
- Shrinkage of gel on storage which causes some liquid to be squeezed out

33
Q

General indication of ointment bases

A

General indications for ointment bases

1) As a vehicle for drug to be applied to the skin
2) As an emollient

34
Q

The greatest resistance to drug penetration is exerted by the ______

A

stratum corneum

35
Q

Drug absorption through the skin is enhanced by_________

A

hydration of stratum corneum

coz it opens the intercellular space; space at corneum increase

36
Q

Drug absorption through the walls of hair follicles, sweat glands and oil glands is relatively less significant

A

Drug absorption through the walls of hair follicles, sweat glands and oil glands is relatively less significant

37
Q

Advantage of gel

A

Evaporate fast
non-greasy
easy to washoff

38
Q

Ointment properties that affect drug bioavailability to the skin

A
  1. Type of ointment base
  2. Viscosity of ointment base
  3. Interaction between ointment base and drug
  4. Partition coefficient of drug between base and skin
  5. Charges on drug molecules
  6. Size of drug molecules
  7. Amount of drug in ointment base 8.Presence of penetration enhancers in ointment base
39
Q

factors to consider when choosing and ideal ointment base

A

1) dermatological factor

2) pharmaceutical factor

40
Q

Dermatological factors when choosing ointment base

A

1) Base should release drug readily to skin -Influenced by partition coefficient of drug between the base and skin

2) Base should facilitate drug absorption by skin
- Influenced by ability of base to penetrate and hydrate skin

3) Base should not interfere with normal skin functions (e.g.perspiration) or cause irritation (e.g.edema and rashes)
- Influenced by extent of occlusion due to the base

4) Base should be miscible and compatible with skin secretions
- Influenced by type and pH of base
- pH of base should be close to that of the skin (pH~5.5)
- Miscible base enhances drug absorption

5) Base should have good emolliency
- Influenced by type of base
- Oleaginous bases have excellent emolliency

6) Base should be easy to apply and remove
- Influenced by type of base
- Oleaginous bases are difficult to remove

41
Q

Pharmaceutical factors that should be considered when chooising type of ointment bases

A

1) Base should be chemically and physically stable
- Vegetable oils are more problematic than mineral oils

2) Base should have good solvent property
- Affects homogeneity of the product

3) Base should have good emulsifying property
- Affects ease of incorporating aqueous drug solution

4) Base should have suitable consistency
- Affects drug distribution, ease of production and administration

42
Q

Ophthalmic ointment composition

A

eg yellow soft paraffin combined with liquid paraffin (decrease consistency) and waxy substances (increase consistency)

mostly uses oleaginous base coz need to stay on eye for long.

white paraffin is contraindicated.
and sterility is legal obligation.

43
Q

Rectal ointment properties

A

Oleaginous bases are preferred

and should be thinner and softer than skin ointment

44
Q

how to prepare ointment

A

2 methods

incorporation method
fusion method

methods employed depends on the nature of the ointment components

45
Q

explain incorporation method

A

use to prepare an ointment

in this method, no heating is employed. the base is prepared by blending its components.
it is then mixed with the drug to obtain a homogeneous product.

Advantage: appropriate for thermolabile drug
Limitation: if waxy solid substance is involved then this method cant be used (waxy solid + aq soln is not suitable)

More suitable for small scale production
- mortar and pestle
- ointment slab and spatula 
2 type of ointment slab
- clear and grounded
- grounded is better as it is rough and thus provide friction; blending is more efficient

3 ways to achieve this method
1) mix base and drug (large amount) into different mixture
then combine these mixtures.

2) by geometric dilution(base amount is small)
3) Mix small amount of liquid drug and base a few times

46
Q

What is fusion method

A

Use to make ointment

  • In this method,heating is employed
    Recommended if components such as beeswax, hard paraffin wax, stearyl alcohol and PEGs of high molecular weight are used
    Suitable for both small scale and large scale production
    equipment used include Porcelain dish;steam-jacketed kettle
    Different techniques for emulsion and non-emulsion bases

1) Preparation of non-emulsion base
The ointment components are melted together and cooled with constant stirring until congealed.
The drug may be added during or after preparation of the ointment base.

2)Preparation of emulsion base
we have the oil soluble components and water soluble components which are the oil phase and aq phase respectively. depending on the solubility of the drug it can be mix with either the oil or aq phase.

each phase are then melted at 70degree and then mixed together (either adding DP to CP or opposite)

and then stir till cool forming ointment base which has been congealed.

the drug or perfume can then be added at this stage.
further homognisation is then carried out to enhance stability. forming ointment

47
Q

How to prepare Gel

A

2 methods

1) direct hydration
2) special individualized procedures

1) Add the gelling agent to the dispersion medium.
Dispersion may be facilitated by agitation or temperature modification of the dispersion medium.
(1 phase gel)

2) Preparation of aluminium hydroxide gel and bentonite gel.
(2 phase gel)

48
Q

why cant add dispersion medium to gelling agent in direct hydration method?

A

Gelling agent often exist mass chunk.

so when dispersion medium is added to gelling agent the outer part will be hydrated so it become difficult for the medium to enter the gelling agent making the preparation lumpy and difficult to disperse.

49
Q

how to prepare aluminium hydroxide gel

How to prepare bentonite gel

A

alcl + NaHCO3/NH4HCO3
–> AlOH gel

Add small amount of bentonite in to dispersion medium (repeat)
- need to stand overnight

50
Q

how are ointment package

A

Jar or tubes
either color or colorless

2 types of tube

  • collapsible
  • non collapsible
51
Q

high pressure filler

A

use to pack semi-solid ointment into jar.

52
Q

how to evaluate ointment

A

1) Penetration of ointment base into skin
2) Drug release from ointment
3) Absorption of drug into blood stream 4)Irritant effect
5) Stability 6)Microbiological quality

53
Q

Eqn for penetration of ointment

A

Ws = Wo - Wt

where
Ws= weight of ointment base absorbed per unit area of skin
Wo = weight of ointment base applied per unit area of skin Wt= weight of ointment base left on the skin after a given length of time

54
Q

how to measure drug released from ointment

A

1) test tube methods
- line inner tube with ointment and fill with dissolution medium
- measure dissolution medium at different time point

2) jar method
- ointment is filled into small jar covered with cellophane
- fill with dissolution medium
- measure aliquot at different time point

  • testtube method will give a faster release as it has higher SA and no barrier (no cellophane)
55
Q

how to find out drug absorption into blood stream

A

Ointment applied to skin and blood or urine obtained over time for drug assay

56
Q

how to find out irritant effects

A

Reaction of skin/eyes of rabbits or skin of human beings to the ointment is determined at specific time intervals -Draize dermal irritation test in rabbits
-21-Day cumulative irritation study (on human)

Typical erythema scores

0-no visible reaction
1-mild erythema 
2-intense erythema 
3-intense erythema with edema 
4-intense erythema with edema and vesicular erosion and vesicular erosion
57
Q

How to evaluate physical and chemical stability

A

ointments are evaluated under normal or accelerated conditions
(is there phase separation or [] got decrease)

58
Q

how to determine microbiological quality

A

measure microbial content and preservative efficacy .

59
Q

BP and USP methods for determining preservative efficacy of ointment

A

4 bacteria used separately

  • SAureus
  • P aeruginosa
  • C. albican
  • Asperigillus niger

inoculate bacteria/fungi into container. incubate ointment
withdraw aliquote samples and determine number of viable cells at zero hour and other appropriate time. (2, 7, 14, 28days)

1 criteria to meet
A or B
A is more stringent
B is more lenient

log reduction factor
= log (initial count/count at time t)

Formulation And Technology (14 decks)

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