semisolid dosage form

1. OINTMENTS
DR. R.SAMBATH KUMAR

2. Semisolid dosage forms
 Ointments, creams, and pastes are semisolid dosage forms
intended for topical application. They may be applied to the
skin, used nasally, rectally, and vaginally. Most of them
contain some form of medicament.
There are three main functions of topically applied
pharmaceuticals. These are
 To protect the injured areas from the environment
 To provide skin hydration, or an emollient effect and
 To provide a means of conveying medication to the skin
for a specific effect, either topically or systematically

3. From semisolid dosage forms, the amount of drug
that penetrates into the skin is a function of the
 amount of pressure and vigour or rubbing
 surface area covered
 condition of the skin
 base used and
 occlusive dressings

4. Ointments are homogeneous, semisolid preparations
intended for external application to the skin or certain
mucous membranes for emollient, protective,
therapeutic purposes where a degree of occlusion is
desired.
 Ointment bases used for ointment preparation are of
four types, hydrocarbon bases, absorption bases,
water-removable bases, and water-soluble bases.
1. Hydrocarbon bases have emollient properties and are
effective as occlusive dressings (e.g., Petrolatum,
USP).

5. 2. Absorption bases permit the incorporation of
aqueous solutions to form w/o emulsions
(e.g., hydrophilic petrolatum and lanolin).
3. Water-removable bases are also o/w emulsions
and are water washable (e.g., hydrophilic
ointment).
4. Water-soluble bases have no oleaginous
component and are referred to as greaseless
water-washable bases (e.g., polyethylene glycol
ointment).

6. Definition of ointment base: Ointment base is a soft semisolid vehicle in
which the medicament is in corporate or dispersed or suspended.
Characteristics of an ideal ointment base
1. It should be nonirritating to the skin
2. It should be non greasy
3. It should be non toxic
4. It should be compatible with the medicaments
5. It should be physically and chemically stable
6. It should be smooth and free from grittiness
7. It should be easily removable from the skin
8. It should not be interfere with the normal function of the skin.
9. It should be release the medicament readily when applied on the skin
10. It should be neutral in PH.

7. FACTOR TO BE CONSIDERED IN THE SELECTION OF
OINTMENT BASE
I. DERMATOLOGICAL FACTOR
Absorption and penetration: the ointment base should be readily
penetrating the skin The rate of release and absorption of the
medicament from the ointment base must be greater.
Effect on skin function: the ointment base should not interfere with the
normal function of the skin.
Miscibility with the skin secretions: the ointment base should readily
miscible with skin secretions.
Compatibility with skin secretions: the ointment base should not react
with skin secretion.
Freedom from irritant effect: the ointment base should not have irritation
effect on the skin.
Easy application and removal: application of the ointment base on the
skin and removal from the skin and removal from the skin should be
easier.

8. II.PHARMACEUTICAL FACTORS:
Stability: the ointment base should be physically stable. It
should not decompose or deteriorate on storing for long time.
Solvent properties: the ointment base should have solvent
properties. For example the base selection for phenol
ointment B.P.1948, must be capable of retaining the phenol in
solution.
Emulsifying properties: the ointment base should have
emulsifying properties when the preparation contains aqueous
phase.
Consistency: the official ointment bases are designed to
produce ointments of suitable consistency at room
temperature.

10. 1. Hydrocarbon Bases
Also known as oleaginous bases, the hydrocarbon bases
are essentially water-free, incorporating aqueous
preparations only in small amounts and with
considerable difficulty.
The primary features of this type of base include its
emollient effect, retention on the skin for prolonged
periods, prevention of escape of moisture from the
skin to the atmosphere, and difficulty in washing off.
They act as occlusive dressings (air- and water-tight ),
thus increasing skin hydration by reducing the rate of
loss of surface water.

12. Absorption Bases
 Absorption bases, as such, are hydrophilic, anhydrous
materials (w/o emulsions) or hydrous bases (w/o emulsions
that have the ability to absorb additional water).
 Addition of lanolin, lanolin isolates, cholesterol, lanosterol, or
acetylated sterols renders the hydrocarbon base hydrophilic.
Such hydrophilic mixtures have been known as absorption
bases;
 Although the bases do eventually absorb aqueous solutions to
be considered w/o emulsions.

14. Water-Removable Bases (Water-Washable Creams)
 These are the most commonly used o/w emulsion bases that are
capable of being washed from skin or clothing with water.
 They may contain water-soluble and -insoluble components. From
a therapeutic viewpoint, they have the ability to absorb serous
discharges in dermatologic conditions.
 The water-removable bases form a semipermeable film on the site
of application after the evaporation of water.
 As such, the base consists of three component parts: the oil phase,
the emulsifier, and the aqueous phase. The oil phase, also called
the internal phase, is typically made up of the petrolatum and/or
liquid petrolatum.
 Other ingredients such as cetyl and stearyl alcohol may be added to
make up the oil phase.
 A typical water-removable emulsion base is hydrophilic ointment,
USP, as shown table.

16. Water-Soluble Bases
 These bases contain only water-soluble components. Water-soluble
bases are also referred to as greaseless because of a lack of oleaginous
materials.
 Polyethylene glycols (PEG) make up the majority of components of the
water-soluble base. PEGs may exist as liquids or waxy solids, identified
by numbers that are an approximate indication of their molecular weight.
 The lowest number signifies a liquid state, which transitions to a waxy
solid state as the numbers increase. For example, PEG 400 is a liquid,
whereas PEG 4000 is a waxy solid.
 Polyethylene glycol are nonvolatile, water-soluble, or water-miscible
compounds and chemically inert. PEGs of interest as vehicles include
the 1500, 1600, 4000, and 6000 products, ranging from soft, waxy solids
to hard waxes. PEG, particularly 1500, can be used as a vehicle by itself,
but better results are often obtained using blends of high and low-
molecular-weight glycols as in polyethylene glycol ointment, NF.

17. 
METHOD OF PREPARATION OF
OINTMENT:
Fusion method

Trituration method

Chemical reaction and

Emulsification method.

18. 
1. FUSION METHOD

This method is preferred when the base is hard and
the medicament is soluble in the base. The entire
ingredient such as white bees wax hard paraffine,
white soft paraffin, stearic acid etc., is melted together.
Than medicament is added to the melted base cools
dawn and a homogenous product is formed.

Example; Simple ointment I.P. and Emulsifying
ointment B.P. are prepared by this method.

Simple ointment I.P

Formula: Wool fat, hard paraffin, cetostearyl alcohol,
white or yellow soft paraffin.

19. 
Procedure: melt hard paraffin, cetostearyl alcohol on water
both. To this incorporate wool fat and white soft paraffin.
Stir until all ingredients are melted. Examine the content for
any foreign particles. Stir the mixture thoroughly until cold.
Pack it in a ointment jar, label and dispense.

Application: simple ointment used as an ointment base.

Wool fat promotes the penetration and absorption of the
medicaments.

Hard paraffin acts as a stiffening agent. It gives good
consistency to the preparation.

Cetostearyl alcohol promotes the stability of the preparation.

White or yellow soft paraffin acts as a base.

20. 
2. CHEMICAL REACTION METHOD

Preparation of ointment containing free iodine,
B.P.C

Iodine is slightly in most oils and fats. But when
iodine is combined with potassium iodide, it forms
poly iodide (eg. KI.I2., KI.2I2., KI.2I3.) which are
more soluble in water, alcohol and glycerin.

The solvent used in the preparation should be non
volatile otherwise the medicament may crystallize
when the solvent evaporates. So the glycerin is
chosen as the solvent.

21. 
Formula: iodine, potassium iodide, glycerin, wool fat, yellow
bees wax, and yellow soft paraffin.

Procedure: dissolve iodine and potassium iodide in glycerin
using a glass mortar. Melt the wool fat, yellow bees wax and
yellow soft paraffin in a china dish over a water bath and stir
well. Add the iodine solution to the melted base and mix
thoroughly.

Storage: It is stored in a well closed container and kept in a
cool place.

Use: used in the treatment of myalgia and arthritis.

Action: iodine act as a antiseptic, disinfectant and counter
irritant.

Potassium iodide increases the solubility of iodine.

Glycerin acts as a solvent.

Wool fat yellow bees wax and yellow soft paraffin act as a base.

22. 
Preparation of ointment containing combined iodine
(Non staining iodine ointment B.P.C.

When the fixed oils (arachis oil), vegetable and animal fats
and some paraffins (eg. Wool fat, yellow soft paraffin’s) are
heated with iodine. Such ointments are dark, greenish
black preparations. When this preparation is rubbed into
the skin it is readily absorbed and it does not produce any
stain on skin. Hence it is called non staining iodine
ointment.

Formula: iodine, arachis oil, and yellow soft paraffin.

23. 
Procedure: finely powder the iodine and placed in a well
closed bottle containing arachis oil, and yellow soft paraffin.
Heat with this bottle with all the ingredient on a water both at
a temperature not exceeding 60oC, stirring occasionally for 2
to 6 hours until the reaction is completed, transfer the product
to the final container and allow it to cool

Storage: it is stored in a well closed container and kept in a
cool place.

Use: iodine used in the treatment of myalgia and arthritis.

Action: iodine act as a antiseptic, disinfectant and counter
irritant.

24. 
EMULSIFICATION METHOD:

In emulsification method, an ointment emulsion is
formed if a non fatty liquid (ie., one which miscible
with fats) is distributed through the solid fat by
triturating. Depending up on the emulsifying agent used
in the preparation. Ointment emulsions may be
classified in to five groups namely

Wool fat emulsions.

Wool alcohol emulsions

Bees wax emulsions

Soap emulsions

Synthetic wax emulsions.

25. 
WOOL FAT EMULSIONS.

Wool fat emulsion is formed by mixing wool fat with
hot water.

Example : Hydrous wool fat B.P.C

Formula: wool fat, purified water freshly boiled and
cooled.

Procedure: melt the wool fat. To this add hot water
(50oC) gradually with constant stirring.

Storage: It is stored in a air tight containers and kept
in cool place.

Use: it is used as an ointment base for preparing other
ointment preparations. The resulting preparation is of
water in oil type.

26. 
WOOL ALCOHOL EMULSION

Example : Oily cream, B.P.

Formula: wool alcohol, hard paraffin, white soft paraffin,
liquid paraffin and purified water.

Procedure: melt wool alcohol, hard paraffin, white soft
paraffin and liquid paraffin in a china dish over water both. To
this melted base, add hot water (50oC) gradually with constant
stirring until smooth cream is formed.

Storage: it should be stored in a well closed container.

Use: it is used as an ointment base for preparing other
ointment preparation. This resulting preparation is of water in
oil type.

27. 
BEES WAX EMULSION.

Bees wax emulsion is prepared by mixing bees wax with hot water.

Cold cream, B.P.C.

Formula: White Bees wax, hard paraffin, white soft paraffine,
borax, liquid paraffin, glycerin and water.

Procedure: melt the White Bees wax, hard paraffin and white soft
paraffin at70oC. To this add liquid paraffin and glycerin and
maintain the temperature at 70oC. Dissolve borax in water and heat
at 70oC. Add the hot borax solution to the melted base and stirring
vigorously. Maintain the temperature at 70oC during stirring.
Continue the stirring until smooth semisolid cream is formed.

Storage: it is stored in a well closed container.

Use: used as cosmetic and also used as a base preparing other
ointment preparation is of water in oil type.

28. 
SOAP EMULSION.

Most vegetable oil and animal fats contain small proportion of
free fatty acid which combines with alkaline substance (borax,
ammonia) to form soap. The resulting preparation is of oil in
water type.

Example : Hydrous ointment B.P.C.

Formula: white bees wax, borax, almond oil, rose oil and rose
water.

Procedure: melt the white bees wax and almond oil at 70oC.
Dissolve borax in a rose water and heated at 70oC. Add this hot
solution in to the melted base and stir vigoursely. Maintain the
temperature at 70oC during stirring. Continue the stirring until
smooth semi solid cream is formed.

Storage; It is stored in a well close container.

Use: It is used as a base for preparing other ointment.

29. 
SYNTHETIC WAX EMULSION

Synthetic waxs are used in formulating emulsifying ointments.
Emulsifying wax is an example for synthetic wax. Emulsifying wax is
used for the preparing emulsifying ointment.

Example : Aqueous cream, B.P.C.

Formula; Sodium lauryl sulphate, cetostearyl alcohol, liquid paraffin,
and white soft paraffin, cholorocresol and purified water.

Procedure: Melt the Sodium lauryl sulphate, cetostearyl alcohol, liquid
paraffin, and white soft paraffin at 70oC. Dissolve the cholorocresol in
purified water at 70oC. Add the cholorocresol solution to the melted
base and stir vigorously. Maintain the temperature at70oC during stirring.
Continue the stirring until smooth semisolid cream is formed.

Storage: it should be stored in a well closed container.

Use: it is used as an antiseptic.

30. 
STABILITY OF OINTMENTS

A stable ointment is one which retains its homogeneity
throughout its life period. The stability study of an ointment
including visual appearance, change of color, odour, viscosity,
softening range consistency, homogeneity, particle size
distribution and sterility.

PACKING OF OINTMENT

Generally ointments are packed in the ointment jars or
collapsible tubes. Amber colored glass jars are used for light
sensitive preparations. Whiling 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.

31. 
STORAGE OF OINTMENTS

Ointment should be stored in well closed containers and in a
cool place. It should be protected from light. High
temperatures cause deterioration of ointments.

LABELLING

Ointment jars are labeled with self adhesive labels. A cello
tape can be wrapped around the lable. Self adhesive strip
labels are used because the ordinary gummed labels do not
stick well on the surface of the container. Labeled should be
attached to the top of the collapsible tube so that will not be
destroyed until the tube is empty. Before the label is pasted,
the collapsible tube may be tipped in compound benzoin
tincture and allowed to dry. Than the labels in strip form are
pasted around the tube. In large scale operations, the label is
printed or embossed on the tube itself.

32. 
Evaluation of ointments

Drug content

Release of medicament from base

Medicament penetration

Consistency of the preparation

Absorption of medicament into blood stream

Irritant effect