ointments are semi-solid preparations which are medicated as well as non-medicated formulations.

1. SEMISOLID DOSAGE
FORMS- OINTMENT
SAGAR KUNDLAS
B. PHARMACY
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2. MAHARAJA AGRASEN UNIVERSITY
(SCHOOL OF PHARMACY)
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3. INTRODUCTION
 Pharmaceutical semisolid preparations include ointments, pastes, cream emulsions,
and gels. Their common property is the ability to cling to the surface of application
for reasonable duration before they are washed or worn off. This adhesion is due to
their plastic rheological behaviour, which allows the semisolids to retain their shape
and cling as a film until acted upon by an outside force.
 Ointments are semisolid preparations intended for external application to the skin
or mucous membranes. Ointments may be medicated or not. Unmedicated
ointments are used for the physical effects they provide as protectants, emollients,
or lubricants.
 Ointments are fatty preparations that are usually self-occlusive and are generally
used on dry lesions. Unmedicated ointments are used as emollients to soothe,
smooth and hydrate dry skin conditions
 Ointments, in general, are composed of fluid hydrocarbons meshed in a matrix of
higher-melting solid hydrocarbons.
 An ointment is classified as any semi-solid containing fatty material and intended
for external application (U.S. Pharmacopeia).
 In 19th century, ointments were based on lard, a compounding material, the
usefulness of which was severely limited by its tendency to turn rancid.
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4. ADVANTAGES
 Handling of ointments is easier than bulky liquid dosage forms.
 They are chemically more stable than liquid dosage forms.
 They facilitate application of the directly to the effected body part and
avoid exposure of other parts to the drug.
 They are suitable for patients who find it difficult to take the drugs by
parenteral and oral routes.
 They prolong the contact time between the drug and effected area.
 The bioavailability of drugs administered as ointments is more since it
prevents passage through liver.
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5. DISADVANTAGES
 They are bulkier than solid dosage forms.
 When applications of an exact quantity of ointment to the affected area is
required, it is difficult to ascertain the same.
 They are less stable than solid dosage forms.
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6. OINTMENT BASES (VEHICLE)
 The vehicles used for a pharmaceutical semisolid are called as bases and
they differ from that used for cosmetics because for a cosmetic,
penetration into skin is not desired. Penetration or protection is desired in
a pharmaceutical semisolid, and its cosmetic effect or appearance on the
skin is less important. The solubility and stability of the drug in the base,
as well as the nature of the skin lesion, determine the choice of the
semisolid vehicle.
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7. Contd.
 The USP recognizes four classes of semisolid bases under the general
classification of ointment:
OINTMENT BASES
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WATER
REMOVABLE
BASES
WATER
SOLUBLE
BASES
ABSORPTION
BASES
OLEAGINOUS
BASES

8. OLEAGINOUS BASES
 These bases are usually anhydrous and consist of substances such
hydrocarbons, vegetable oils, silicones and certain synthetic esters, either
alone or in combination. These bases are characterised by (i) low capacity
to absorb water (emollient effect), (ii) exert high occlusiveness by forming
water impermeable layer of skin, (iii) greasy and thus difficult to remove
from skin, (iv) prolonged contact with skin and (v) poor aesthetic appeal.
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9. Contd.
 Hydrocarbons Bases: These bases include hard, liquid, and soft paraffins
1. Soft paraffin (petrolatum): The most common base used in ointment
because of its consistency, its bland and neutral characteristics, and its
ability to spread easily on the skin.
2. Liquid paraffin (mineral oil): It is obtained from petroleum, as is
petrolatum, by collection of a particular viscosity-controlled fraction. Soft
petrolatum is a mixture of 90% white petrolatum with 10% mineral oil.
3. Hard paraffin (hydrocarbon waxes): These waxes are used to increase
viscosity of the mineral oil in creams and ointments, as it prevents the
separation.
 Vegetable oils: such as peanut oil, almond oil, sesame oil and olive oil are
mono-, di-, and tri glycerides mixtures of unsaturated and saturated fatty
acids.
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10. ABSORPTION BASES
 These bases are usually anhydrous and they do absorb aqueous solutions
and can be considered water-in-oil emulsions. These bases do not
absorb water on contact, but with sufficient agitation.
 Absorption bases are of two types:
 (a) Anhydrous absorption bases: those that permit the incorporation of
aqueous solutions resulting in the formation of water-in-oil (W/O)
emulsions (e.g., hydrophilic petrolatum). Anhydrous lanolin is capable of
absorbing about 30-50% of its weight of water to form an emulsion.
 (b) Hydrous absorption bases: those that are W/O emulsions(syn:
emulsion bases) that permit the incorporation of additional quantities of
aqueous solutions (e.g., lanolin).These bases may be used as emollients,
although they do not provide the degree of occlusion afforded by the
oleaginous bases.
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11. WATER REMOVABLE BASES
 Water-removable bases are oil-in-water emulsions commonly called
creams. Because the external phase of the emulsion is aqueous, they are
easily washed from skin and are often called water-washable bases. They
may be diluted with water or aqueous solutions. Hydrophilic Ointment,
USP, is an example of this type of base.
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12. WATER SOLUBLE BASES
 Water-soluble bases do not contain oleaginous components. They are
completely water washable and often referred to as greaseless. Because
they soften greatly with the addition of water, large amounts of aqueous
solutions are not effectively incorporated into these bases. They mostly
are used for incorporation of solid substances. Polyethylene glycol (PEG)
ointment, NF, is the prototype example of a water-soluble base.
Polyethylene Glycol Ointment, NF, PEG is a polymer of ethylene oxide and
water represented by the formula H(OCH2CH2)nOH, in which n
represents the average number of oxyethylene groups.
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13. Oleaginous Ointment Bases Absorption Ointment Bases Water/Oil Emulsion Ointment
Bases
Oil/Water Emulsion Ointment
Bases
Water-miscible Ointment
Bases
Composition oleaginous compounds oleaginous base + w/o
surfactant
oleaginous base + water (<
45% w/w) + w/o surfactant
(HLB <8)
oleaginous base + water (>
45% w/w) + o/w surfactant
(HLB >9)
Polyethylene Glycols
(PEGs)
Water Content anhydrous anhydrous hydrous hydrous anhydrous, hydrous
Affinity for Water hydrophobic hydrophilic hydrophilic hydrophilic hydrophilic
Spreadability difficult difficult moderate to easy easy moderate to easy
Washability Non-washable Non-washable non- or poorly washable washable washable
Stability oils poor; hydrocarbons
better
oils poor; hydrocarbons better unstable, especially alkali soaps
and natural colloids
unstable, especially alkali
soaps and natural colloids;
non-ionic better
stable
Drug Incorporation
Potential
solids or oils (oil soluble only) solids, oils, and aqueous
solutions (small amounts)
solids, oils, and aqueous
solutions (small amounts)
solid and aqueous solutions
(small amounts)
solid and aqueous
solutions
Drug Release Potential* poor poor, but > oleaginous fair to good fair to good good
Occlusiveness yes yes sometimes no no
Uses protectants, emollients (+/-
), vehicles for hydrolysable
drugs
protectants, emollients (+/-),
vehicles for aqueous solutions,
solids, and non-hydrolysable
drugs
emollients, cleansing creams,
vehicles for solid, liquid, or
non-hydrolysable drugs
emollients, vehicles for solid,
liquid, or non-hydrolysable
drugs
drug vehicles
Examples White Petrolatum, White
Ointment
Hydrophilic Petrolatum,
Anhydrous Lanolin,
Aquabase™, Aquaphor®
Cold Cream type, Hydrous
Lanolin, Rose Water Ointment,
Hydrocream™
Hydrophilic Ointment,
Dermabase™, Velvachol®,
Unibase®
PEG Ointment, Polybase™
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14. Selection of the Appropriate Bases
 Selection of the base to use in the formulation of an ointment depends
on careful assessment of a number of factors, including the following:
 Desired release rate of the drug substance from the ointment base
 Desirability of topical or percutaneous drug absorption
 Desirability of occlusion of moisture from the skin
 Stability of the drug in the ointment base
 Effect, if any, of the drug on the consistency or other features of the
ointment base
 Desire for a base easily removed by washing with water
 Characteristics of the surface to which it is applied
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15. Various Methods of Ointment’s
Preparation
 Ointments are prepared by two general methods, depending primarily on
the nature of the ingredients.
METHODS
1. Incorporation Method
2. Fusion Method
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16. INCORPORATION METHOD
 The components are mixed until a uniform preparation is attained. On a
small scale, as in extemporaneous compounding, the pharmacist may mix
the components using a mortar and pestle, or a spatula may be used to
rub the ingredients together on an ointment slab (a large glass or
porcelain plate or pill tile). Others will use an ointment mill, an electronic
mortar and pestle, or a device called an “Unguator,” (Fig. 1) which allows
a pharmacist to place the ingredients in a plastic ointment jar with a
special lid that allows for a mixing blade to be used to mix the ingredients
in the dispensing container.
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17. Contd.
 Ointment or roller mills can be used to force coarsely formed ointments
through stainless steel or ceramic rollers to produce ointments uniform in
composition and smooth in texture (Fig. 2). Small ointment mills also find
use in product development laboratories and in small-batch manufacture
or compounding.
Fig 1. Unguator Electronic mortar and pestle. Fig. 2 Ointment roller mill
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18. Fusion Method
 By the fusion method, all or some of the components of an ointment are
combined by being melted together and cooled with constant stirring
until congealed. Components not melted are added to the congealing
mixture as it is being cooled and stirred. Naturally, heat-labial substances
and any volatile components are added last, when the temperature of the
mixture is low enough not to cause decomposition or volatilization of the
components. Substances may be added to the congealing mixture as a
solution or as insoluble powders levigated with a portion of the base. on
a small scale, fusion may be conducted in a large scale, it is carried out in
large steam jacketed kettles. Once congealed, the ointment may be
passed through an ointment mill (in large-scale manufacture) or rubbed
with a spatula or in a mortar to ensure a uniform texture.
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19. ROUTES OF PENETRATION
 When a drug system is applied topically, the drug diffuses out its vehicle
onto the surface tissues of the skin. There are three potential portals of
entry: through the follicular region (transfollicular), through the sweat
ducts, or through the unbroken stratum corneum between the
appendages(transrpidermal). There is little convincing evidence that
eccrine sweat glands play any significant role in cutaneous permeability.
Material may enter the ducts, and to be no penetration from these areas
to the dermis.
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20. 20

21. Contd.
 Once a substance passes through the stratum corneum, there is
apparently no significant further hindrance to penetration of the
remaining epidermal layers and corium, there is then a ready entry into
the circulation via the capillaries. The concentration gradient essentially
ends in the dermal layer at the beginning of the circulation. The systemic
circulation acts as a reservoir or “sink” for the drug.
 Diffusion through the horny layer is a passive process. There is little
evidence to support specialized active transport systems for cells of the
stratum corneum. The passive process is affected only by the substance
being absorbed, by the medium in which the substance is dispersed, and
by ambient conditions.
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22. EVALUATION OF OINTMENT
 There are some tests for evaluation of the ointment formulation and
some are as follow:
1. Rate of absorption
2. Non-irritancy
3. Rate of penetration
4. Rate of drug release
5. Rheological properties
6. Content uniformity
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23. Test for rate of absorption
 The diadermatic ointment should be evaluated for the rate of absorption
of drug into the blood stream. This test can be done in-vivo only.
 The ointment should be applied over a definite area of the skin by
rubbing.
 At regular intervals of time, serum and urine samples should be analysed
for the quantity of drug absorbed.
 The rate of absorption i.e., the amount of drug absorbed per unit time
should be more.
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24. Test for non-irritancy
 The bases used in the formulation of ointments may cause irritation or
allergic reactions.
 Non-irritancy of the preparation is evaluated by patch test.
 In this test 24 human volunteers are selected.
 Definite quantity of ointment is applied under occlusion daily on the back
or volar fore arm for 21 days.
 Daily the type of pharmacological action observed isnoted.
 No visible reaction or erythema or intense erythemawith edema and
vesicular erosion should occur.
 A good ointment base shows no visible reaction.
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25. Test for rate of penetration
 The rate of penetration of a semisolid dosage form is crucial in the onset
and duration of action of the drug.
 Weighed quantity of the preparation should be applied over selected
area of the skin for a definite period of time.
 Then the preparation left over is collected and weighed.
 The difference between the initial and the final weights of the preparation
gives the amount of preparation penetrated through the skin and this
when divided by the area and time period of application gives the rate of
penetration of the preparation.
 The test should be repeated twice or thrice.
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26. Test for rate of drug release:
 To assess the rate of release of medicament, small amount of the
can be placed on the surface of nutrient agar contained in a petri dish or
alternately in a small cup cut in the agar surface.
 If the medicament is bactericidal the agar plate is previously seeded with
suitable organism like Staphylococcus aureus.
 After a suitable period of incubation, the zone of inhibition is measured
and correlated with the rate of release.
Test for content uniformity:
 The net weight of contents of ten filled ointment containers are
determined.
 The results should match each other and with the labelled quantity.
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27. Reference
 Lachman/ Lieberman’s, The Theory and Practice of Industrial Pharmacy,
Fourth Edition, by CBS Publishers.
 Aulton’s Pharmaceutics, The Design and Manufacture of Medicines,
Fourth Edition, by Elsevier Ltd.
 Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems,
Tenth Edition, by Lippincott Williams & Wilkins, a Wolters Kluwer business.
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