OINTMENTS
Ointments are soft semi-solid
preparations containing medicaments meant for external application to the skin
or mucous membrane.
Types/classification of ointments:
1. Dermatological ointments: Ointment
applied on the skin.
2. Ophthalmic ointment: Ointment
introduction into the ophthalmic cavity
3. Rectal ointment: Ointment applied
in the rectum
Ointment base
Ointment base is a soft semisolid
vehicle in which medicaments is incorporated or dispersed or suspended.
Requirements of ideal ointment base:
1.
The absorption
and penetration should be high.
2.
It is compatible
with skin secretions.
3.
It is miscible
with skin secretions.
4.
It should be
compatible with many ingredients.
5.
It should be
smooth & pourable.
6.
It should
chemically stable & physiologically inert.
7.
It should be
non-toxic, non-irritant & non-sensitive.
8.
It should be
easily washable.
9.
It should be
non-staining.
10. It should release the incorporated medicament readily.
Types of ointments bases:
The ointment various bases are classified into
1. Oleaginous bases
2. Absorption bases
3. Emulsion bases
4. Water soluble bases
1. Oleaginous bases:
These consist of water insoluble
hydrophobic oils & fats. They may contain a single hydrophobic substances
or combination of two & more substances.
They are: Non-greasy, Anhydrous,
Hydrophobic, Insoluble in water, Non-washable
They do not release the
medicament easily.
They are very difficult to
remove the skin.
Ex: Soft paraffin, Hard paraffin, Liquid paraffin, Castor oil, Coconut
oil
2. Absorption bases:
They can absorb a large amount of
water due to their high water number they are: Anhydrous, Hydrophilic (water
can be incorporated)
Insoluble in water, Not water
washable
Ex:
Wool fat, Wool alcohol, Cholesterol, Bees wax
Advantages:
1.
They are compatible with majority of medicament.
2.
They are heat stable.
3.
These bases may be used either in anhydrous form or in emulsified form.
4.
They can absorb a large quantity of water or aqueous substances.
3. Emulsion bases:
Emulsions bases are classified into
1. Oil in water type:
This type of ointment base is hydrous,
hydrophilic, and insoluble in water & water washable. Ex: Emulsifying wax,
Sodium lauryl sulphate.
2. Water in oil type:
This type of ointment base is hydrous,
hydrophilic, and insoluble in water & not water washable. Ex: Wool alcohol,
Wool fat and bees wax
3.
Water soluble bases: They are
anhydrous, hydrophilic, and soluble in water & water washable.Ex: Poly
ethylene glycol, Sodium carboxyl methyl cellulose, Glycerol mono-stearate.
Factors which govern the selection of
an ideal base for ointments:
There are two factor:
I.
Dermatological
factors
II.
Pharmaceutical
factors
I) Dermatological factors:
1. Absorption & penetration: Absorption is systemic absorption & entry into the stream
while penetration means passage through the skin.
Ex:
Cutaneous absorption, Penetration of the ointment occurs through
1. Hair follicle.
2. Sebaceous glands.
3. Non keratinized cells.
2. Effect of skin function: The greasy base interferes with normal skin functions. They are
irritant to the skin. O/w emulsion bases are more compatible with skin function
& having cooling effect rather than healing effect & mix readily with
skin secretions. The ointment base should not interfere with normal skin
functions.
3. Miscibility with skin secretions: The skin secretions are oily as well as aqueous. Emulsion bases
are readily miscible with secretions.
4. Freedom for irritant effect: Ointment base should not cause any irritation to the skin.
5. Compatibility with skin secretions: The ointment base should not react with skin secretions.
6. Emollient properties: Dryness & brittleness of skin cause dis-comfort, so ointment
base should have emollient. Ex: Wool
fat has the good emollient property.
7. Ease of application and removal: Water miscible bases are readily removed by simple washing with
water.
II) Pharmaceutical factors:
1.
Stability: Fats and oils
obtained from animal and vegetable sources are liable to undergo oxidation
unless they are suitably preserved. Liquid paraffin is also stable but on
prolonged storage it gets oxidised therefore an antioxidant like tocopherol may
be incorporated.
2.
Solvent properties: Most of
the medicaments used in the preparation of ointment are insoluble in the
ointment bases therefore they are finely powdered and distributed uniformly
through the base.
3.
Emulsifying properties: Hydrocarbon
bases can absorb only a small amount of aqueous substances where as animal fats
can absorb an appreciable amount of water.
4.
Consistency: The ointments
produced should be of suitable consistency. They should neither be too hard nor
too soft. They should be with stand the climatic conditions. The consistency of
an ointment can be adjusted by incorporating a suitable proportion of high
melting point substances like hard paraffin, bees wax etc.
Method of preparation of ointment:
Ointment are prepared by four methods
namely
1. Fusion method: This
method is prepared when the base is hard & the medicaments are soluble in
the base. All the ingredients such as white soft paraffin, stearic acid are
melted together. The medicament is then added to the melted base & stirred
thoroughly until the melted base cools down & a homogenous product is
formed.
Ex: Simple ointment, emulsifying ointment.
2. Triturations method: This method is preferred when the base is soft & the
medicaments are insoluble in the base. All the solid ingredients are finely
powdered & passed through a sieve of appropriate size. Then the medicaments
are insoluble in the base. All solid ingredients are finely powdered &
passed through a sieve of appropriate size. Then the medicaments are triturated
with a small amount of the base on the ointment slab with the help of stainless
steel spatula. To this the remaining quantities of the base are added &
triturated until the medicaments are homogeneously mixed with the base. The
ointment is passed (if necessary) through an ointment until mill to remove the
gritty particles.
Ex: Sulphur ointment, Boric acid ointment.
3. Chemical reaction method: Certain ointments containing free iodine combined iodine are
prepared by chemical reaction method.
Ex: Ointment containing free
iodine: Iodine is slightly soluble in most fats & oils. But when iodine
is combined with Kl, I forms poly-iodides which are more soluble in water,
alcohol & glycerine. The solvent used in this preparation should be
non-volatile otherwise the medicament may crystallize when the solvent
evaporates. So glycerine is choosen as solvent.
Formula:
Iodine, KI, Glycerine, Wool fat, Yellow bees
wax, Yellow soft paraffin.
Procedure:
Dissolve iodine & Kl in glycerine using a
glass motor. Melt the wool fat, yellow bee’s wax & yellow soft paraffin in
a china dish over a water bath & stir well. Add the iodine solution to the
melted base & mix thoroughly.
Storage: It is stored in well closed container and kept in a cool place.
Use: Used in the treatment of myalgia and arthritis.
Action: Iodine acts as anti-septic, disinfectant and counter irritant. Kl
increases the solubility of iodine. Glycerine acts as a solvent. Wool fat,
yellow soft paraffin acts as base.
4. Emulsification method: In emulsification method, an ointment emulsion is formed if a
non-fatty liquid (one which is immiscible with fats) is distributed throughout
a solid fat by trituration. Ex: Wool fat emulsion, Wool alcohol emulsion, Bees wax emulsion. Soap emulsion
Storage of ointments:
Containers:
Generally ointments are packed in ointment
jars or collapsible tubes. Amber coloured glass jars are used for light
sensitive preparation. While filling the ointment jars care must be taken to
avoid the entrainment of air, packing of ointments in collapsible tubes are
more hygienic. Collapsible tubes are made up of tin.
Storage: Ointments should be stored in well closed containers and in a
cool place. It should be protected from light, high temperature cause
deterioration of ointments.
Labelling: “for external use only”
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