Ointments and Ointment Bases in Pharmaceutics

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

Semisolid dosage forms arise from the fact that, within

the matrix there are liquid molecules, but it is either

solid or liquid-crystalline material blended within the

matrix that provides the body or consistency to the

matrix.



They fulfill a special topical need by being able to cling

to the surface of the skin for a protracted period,

generally until being washed off or worn off.



Lotions have poor adhesiveness and may readily flow

off the applied area.

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

Ointments

:

 semisolid preparations intended for external

use.  (Ophthalmic ointments are a separate

classification.)  it can be medicated or nonmedicated.



If nonmedicated, the ointment is usually referred to as

an ointment base.  Generally, an ointment is

translucent.  An ointment base can be used for its

emollient or lubricating properties or as the vehicle for

a medicated ointment.



An emollient makes skin soft and supple probably by

occluding the skin surface which prevents moisture loss

and allows the underlying material to rehydrate.

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

The vehicle of an ointment is known as ointment base.

The vehicle of an ointment is known as ointment base.

The choice of a base depends upon the clinical

The choice of a base depends upon the clinical

indication for the ointment, and the different types of

indication for the ointment, and the different types of

ointment bases are:

ointment bases are:



Hydrocarbon bases

Hydrocarbon bases

. e.g. hard paraffin, soft paraffin.

. e.g. hard paraffin, soft paraffin.



Absorption bases

Absorption bases

. e.g. wool fat, beewax.

. e.g. wool fat, beewax.



Water soluble bases

Water soluble bases

. e.g. macrogols 200,300,400.

. e.g. macrogols 200,300,400.



The medicaments are dispersed in the base and later

The medicaments are dispersed in the base and later

they get divided after the drug penetration into the

they get divided after the drug penetration into the

living cells of skin.

living cells of skin.

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

Drug content



Release of medicament from base



Medicament penetration



Consistency of the preparation



Absorption of medicament into blood

stream



Irritant effect.

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

Hydrocarbon bases:

Hydrocarbon bases:

 water free, oleaginous compounds

 water free, oleaginous compounds

which used principally for their emollient effect.

which used principally for their emollient effect.



They are retained on the skin for a long time, do not permit

They are retained on the skin for a long time, do not permit

evaporation of moisture from the surface of the skin

evaporation of moisture from the surface of the skin

(occlusive dressing), and are difficult to wash off.

(occlusive dressing), and are difficult to wash off.

Petrolatum, white petrolatum and mineral oil fall into this

Petrolatum, white petrolatum and mineral oil fall into this

classification.

classification.



 In general, fluid hydrocarbons, usually 16 to 30 carbon

 In general, fluid hydrocarbons, usually 16 to 30 carbon

straight-chain and branched molecules are entrapped in a

straight-chain and branched molecules are entrapped in a

fine crystalline matrix of 30 to 50 carbon molecules.

fine crystalline matrix of 30 to 50 carbon molecules.



If the base is melted and then slowly cooled, they tend to be

If the base is melted and then slowly cooled, they tend to be

more fluid than when rapidly cooled since fewer and larger

more fluid than when rapidly cooled since fewer and larger

crystals are formed, resulting in less total solid structure.

crystals are formed, resulting in less total solid structure.

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

Silicone ointments:

Silicone ointments:

 contains polydimethylsiloxane oil as the

 contains polydimethylsiloxane oil as the

principal ingredient.  The semisolid character is due to a wax

principal ingredient.  The semisolid character is due to a wax

or other high melting agent which is blended with the silicone.

or other high melting agent which is blended with the silicone.



These ointments are also excellent at providing a water-

These ointments are also excellent at providing a water-

barrier on the surface of the skin and have been used as

barrier on the surface of the skin and have been used as

emollients.

emollients.



On the negative side, hydrocarbon bases and silicone

On the negative side, hydrocarbon bases and silicone

ointments are considered greasy, and they stain clothes.  The

ointments are considered greasy, and they stain clothes.  The

principal ingredients are not good solvents for drugs and may

principal ingredients are not good solvents for drugs and may

compromise drug availability.

compromise drug availability.



This solubility disadvantage can be overcome by incorporating

This solubility disadvantage can be overcome by incorporating

a miscible cosolvent which possesses a broader capacity to

a miscible cosolvent which possesses a broader capacity to

dissolve drugs.

dissolve drugs.

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

Absorption bases:

Absorption bases:

 two types: (1) those that permit

 two types: (1) those that permit

incorporation of aqueous solutions, resulting in a w/o

incorporation of aqueous solutions, resulting in a w/o

emulsion (Hydrophilic petrolatum and anhydrous lanolin

emulsion (Hydrophilic petrolatum and anhydrous lanolin

fall into this category) and (2) those that are already w/o

fall into this category) and (2) those that are already w/o

emulsions, the so-called emulsion bases, that permit

emulsions, the so-called emulsion bases, that permit

incorporation of a small additional amount of an aqueous

incorporation of a small additional amount of an aqueous

solution (lanolin and cold cream are examples of this

solution (lanolin and cold cream are examples of this

category).

category).



These bases can be used as emollients but are less

These bases can be used as emollients but are less

successful than the hydrocarbon bases which are better

successful than the hydrocarbon bases which are better

able to occlude the skin surface.

able to occlude the skin surface.



Absorption bases are not easily washed off with water.

Absorption bases are not easily washed off with water.

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

Absorption bases:

Absorption bases:



They can be used to introduce an aqueous solution into

They can be used to introduce an aqueous solution into

a hydrocarbon base by first incorporating the solution

a hydrocarbon base by first incorporating the solution

into the absorption base and then incorporating the

into the absorption base and then incorporating the

absorption base into the hydrocarbon base.

absorption base into the hydrocarbon base.



 In this case, an equivalent amount of the hydrocarbon

 In this case, an equivalent amount of the hydrocarbon

base would be substituted with the absorption base.

base would be substituted with the absorption base.

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

Water-removable bases:

Water-removable bases:

 o/w emulsions that can be

 o/w emulsions that can be

washed off the skin or clothing with water.

washed off the skin or clothing with water.



They are the "water-washable" ointment bases although

They are the "water-washable" ointment bases although

they contain water-soluble and water-insoluble

they contain water-soluble and water-insoluble

components.

components.



They may be diluted with water or aqueous solutions. An

They may be diluted with water or aqueous solutions. An

antimicrobial preservative would be incorporated into the

antimicrobial preservative would be incorporated into the

aqueous continuous phase of this base.

aqueous continuous phase of this base.



Hydrophilic ointment is the only example of this type of

Hydrophilic ointment is the only example of this type of

base.

base.

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

Water-soluble bases:

Water-soluble bases:

 These bases contain only water-

 These bases contain only water-

soluble components and therefore can be washed off

soluble components and therefore can be washed off

with water.

with water.



These are the so-called "greaseless" bases because of

These are the so-called "greaseless" bases because of

the absence of oleaginous materials.  Since these bases

the absence of oleaginous materials.  Since these bases

soften when diluted with water, they are not effective

soften when diluted with water, they are not effective

for delivery of aqueous solutions, but are better used for

for delivery of aqueous solutions, but are better used for

incorporation of nonaqueous or solid substances.

incorporation of nonaqueous or solid substances.



Mixtures of the water-soluble polyethylene glycols

Mixtures of the water-soluble polyethylene glycols

(PEG's) are found in this category.

(PEG's) are found in this category.

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

Water-soluble bases:

Water-soluble bases:



Because PEG is linear polymer, polyethylene glycols of

Because PEG is linear polymer, polyethylene glycols of

short chain length are liquids and those of long chain

short chain length are liquids and those of long chain

length are solids at room temperature.

length are solids at room temperature.



A mixture of different types of can be prepared to have

A mixture of different types of can be prepared to have

the desired consistency and drug release properties.

the desired consistency and drug release properties.



Many drugs are soluble in the PEG bases.  In fact,

Many drugs are soluble in the PEG bases.  In fact,

topical drug availability may be poor due to excessive

topical drug availability may be poor due to excessive

drug solubility, which translates to "poor vehicle to skin

drug solubility, which translates to "poor vehicle to skin

partitioning."

partitioning."

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The choice of ointment base depends on several questions:

The choice of ointment base depends on several questions:



What is the desired drug release rate from the ointment

What is the desired drug release rate from the ointment

base?

base?



Should the base enhance skin absorption of the drug

Should the base enhance skin absorption of the drug

(percutaneous absorption)?  e.g., PEG's are believed to

(percutaneous absorption)?  e.g., PEG's are believed to

be skin penetration enhancers.

be skin penetration enhancers.



Should the base occlude the skin?

Should the base occlude the skin?



What is the stability of the drug in the base?

What is the stability of the drug in the base?



Does the drug affect the consistency of the base?

Does the drug affect the consistency of the base?

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

A 

A 

cream

cream

 is a topical preparation usually for application

 is a topical preparation usually for application

to the 

to the 

skin

skin

. Creams for application to 

. Creams for application to 

mucus membranes

mucus membranes

such as those of the 

such as those of the 

rectum

rectum

 or 

 or 

vagina

vagina

 are also used.

 are also used.



Creams may be considered pharmaceutical products as

Creams may be considered pharmaceutical products as

even cosmetic creams are based on techniques

even cosmetic creams are based on techniques

developed by pharmacy and unmedicated creams are

developed by pharmacy and unmedicated creams are

highly used in a variety of skin conditions (dermatoses).

highly used in a variety of skin conditions (dermatoses).



Creams are semi-solid emulsions, that is mixtures of oil

Creams are semi-solid emulsions, that is mixtures of oil

and water. They are divided into 

and water. They are divided into 

two types

two types

: 

: 

oil-in-water

oil-in-water

(O/W) creams

(O/W) creams

 which are composed of small droplets of

 which are composed of small droplets of

oil dispersed in a continuous aqueous phase, and 

oil dispersed in a continuous aqueous phase, and 

water-

water-

in-oil (W/O) creams

in-oil (W/O) creams

 which are composed of small

 which are composed of small

droplets of water dispersed in a continuous oily phase.

droplets of water dispersed in a continuous oily phase.

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

Oil-in-water creams

Oil-in-water creams

 are more comfortable and

 are more comfortable and

cosmetically acceptable as they are less greasy and

cosmetically acceptable as they are less greasy and

more easily washed off using water.

more easily washed off using water.



Water-in-oil creams

Water-in-oil creams

 are more difficult to handle but

 are more difficult to handle but

many drugs which are incorporated into creams are

many drugs which are incorporated into creams are

hydrophobic and will be released more readily from a

hydrophobic and will be released more readily from a

water-in-oil cream than an 

water-in-oil cream than an 

oil-in-water cream

oil-in-water cream

.

.



Water-in-oil creams

Water-in-oil creams

 are also more moisturising as they

 are also more moisturising as they

provide an oily barrier which reduces water loss from the

provide an oily barrier which reduces water loss from the

stratum corneum, the outmost layer of the skin.

stratum corneum, the outmost layer of the skin.

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

The provision of a barrier to protect the skin



To aid in the retention of moisture (especially water-in-

oil creams)



Cleansing



Emollient effects



As a vehicle for drug substances such as local

anaesthetics, anti-inflammatories (NSAIDs or

corticosteroids), hormones, antibiotics, antifungals or

counter-irritants.

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

One of two methods is used to prepare these products:

One of two methods is used to prepare these products:

the 

the 

fusion method

fusion method

 or the 

 or the 

cold incorporation method

cold incorporation method

.

.



Fusion

Fusion

 is used for virtually all o/w creams, which are

 is used for virtually all o/w creams, which are

prepared at high temperatures as liquid emulsions and

prepared at high temperatures as liquid emulsions and

then cooled to the semisolid character at room

then cooled to the semisolid character at room

temperature.

temperature.



Incorporation

Incorporation

 is used when a drug is to be added to an

 is used when a drug is to be added to an

already prepared ointment or cream system or when the

already prepared ointment or cream system or when the

vehicle is heat labile.

vehicle is heat labile.

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

A 

A 

gel

gel

 is an apparently solid, jelly-like material formed from a

 is an apparently solid, jelly-like material formed from a

colloidal solution. By weight, gels are mostly liquid, yet they

colloidal solution. By weight, gels are mostly liquid, yet they

behave like solids due to the addition of a gelling agent.

behave like solids due to the addition of a gelling agent.



A solid 

A solid 

three dimensional network

three dimensional network

 spans the volume of a

 spans the volume of a

liquid medium. The network can be composed of a wide

liquid medium. The network can be composed of a wide

variety of materials, including particles, polymers and

variety of materials, including particles, polymers and

proteins.

proteins.



Cationic polymers are positively charged polymers. Their

Cationic polymers are positively charged polymers. Their

positive charges prevent the formation of coiled polymers.

positive charges prevent the formation of coiled polymers.



Cationic polymers are a main functional component of hair

Cationic polymers are a main functional component of hair

gel, because the positive charged polymers also bind the

gel, because the positive charged polymers also bind the

negatively charged amino acids on the surface of the keratin

negatively charged amino acids on the surface of the keratin

molecules in the hair.

molecules in the hair.

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

Hydrogel

Hydrogel

 is a network of polymer chains that

 is a network of polymer chains that

are water-insoluble, sometimes found as a

are water-insoluble, sometimes found as a

colloidal 

colloidal 

gel

gel

 in which water is the dispersion

 in which water is the dispersion

medium.

medium.



Hydrogels are superabsorbent (they can contain

Hydrogels are superabsorbent (they can contain

over 99% water) natural or synthetic polymers.

over 99% water) natural or synthetic polymers.

Hydrogels also possess a degree of flexibility

Hydrogels also possess a degree of flexibility

very similar to natural tissue, due to their

very similar to natural tissue, due to their

significant water content.

significant water content.

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Common uses of 

Common uses of 

Hydrogel

Hydrogel

 include:

 include:



Currently used as 

Currently used as 

scaffolds in tissue engineering

scaffolds in tissue engineering

. When

. When

used as scaffolds, hydrogels may contain human cells in

used as scaffolds, hydrogels may contain human cells in

order to repair tissue.

order to repair tissue.



Environmentally sensitive hydrogels

Environmentally sensitive hydrogels

. These hydrogels

. These hydrogels

have the ability to sense changes of pH, temperature, or

have the ability to sense changes of pH, temperature, or

the concentration of metabolite and release their load as

the concentration of metabolite and release their load as

result of such a change.

result of such a change.



As sustained-release delivery systems

As sustained-release delivery systems



Contact lenses

Contact lenses

 (silicone hydrogels)

 (silicone hydrogels)

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Common uses of 

Common uses of 

Hydrogel

Hydrogel

 include:

 include:



Breast implants

Breast implants



Dressings for healing of burn

Dressings for healing of burn

 or other hard-to-heal

 or other hard-to-heal

wounds. Wound gels are excellent for helping to create

wounds. Wound gels are excellent for helping to create

or maintain a moist environment.

or maintain a moist environment.



Common ingredients are 

Common ingredients are 

e.g. polyvinyl alcohol

e.g. polyvinyl alcohol

, 

, 

sodium

sodium

polyacrylate

polyacrylate

 and 

 and 

acrylate polymers

acrylate polymers

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

Organogel

Organogel

 is a non-crystalline, non-glassy

 is a non-crystalline, non-glassy

thermoreversible (thermoplastic) solid material

thermoreversible (thermoplastic) solid material

composed of a liquid organic phase entrapped in a

composed of a liquid organic phase entrapped in a

three-dimensionally cross-linked network.

three-dimensionally cross-linked network.



The liquid can be e.g. an organic solvent, a mineral oil or

The liquid can be e.g. an organic solvent, a mineral oil or

a vegetable oil. The solubility and particle is important

a vegetable oil. The solubility and particle is important

characteristics for the elastic properties and firmness of

characteristics for the elastic properties and firmness of

the organogel.

the organogel.



Organogels have potential for use in a number of

Organogels have potential for use in a number of

applications, such as in pharmaceuticals, cosmetics and

applications, such as in pharmaceuticals, cosmetics and

food.

food.

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

Xerogel

Xerogel

 is a solid formed from a 

 is a solid formed from a 

gel

gel

 by drying with

 by drying with

unhindered shrinkage. Xerogels usually retain high

unhindered shrinkage. Xerogels usually retain high

porosity and enormous surface area, along with very

porosity and enormous surface area, along with very

small pore size.

small pore size.



Many substances can form gels when a suitable

Many substances can form gels when a suitable

thickener or gelling agent is added to their formula. This

thickener or gelling agent is added to their formula. This

approach is common in manufacture of wide range of

approach is common in manufacture of wide range of

products, from foods to paints, adhesives.

products, from foods to paints, adhesives.



In fiber optics communications, a soft gel resembling

In fiber optics communications, a soft gel resembling

"hair gel" in viscosity is used to fill the plastic tubes

"hair gel" in viscosity is used to fill the plastic tubes

containing the fibers.

containing the fibers.

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

Stability of the active ingredients



Stability of the excipients



Visual appearance/Color, Odor, and pH



Viscosity



Loss of water or volatile vehicle components



Phase distribution (homogeneity/phase

separation)



Particle size distribution of the dispersed phase



Particulate contamination



Microbial contamination/sterility



Release behavior/availability

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

Obviously, those semisolids that contain water as a

component can support microbial growth with more success

than can the hydrophobic semisolids.



Sterile preparation would involve microbial filtration of the

vehicle, aseptic processing and filling of the container under

laminar-flow hoods.



Most topical products are not intended to be sterile, but

microbial contamination must be controlled.  Microbial

contamination can cause the development of an odor, a

color change, or changes in consistency, with a subsequent

change in the drug release rate.  Frequently, a chemical

antimicrobial preservative is added to inhibit microbial

growth.

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

Examples of topical preservatives include the parabens,

phenols, benzoic acid, sorbic acid, and quaternary

ammonium salts (e.g., benzalkonium chloride).



Protection from microbial contamination can be

accomplished with proper packaging and storage

conditions, which should also protect the product from air,

light, moisture, heat and interactions between the product

and the container material.

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Semisolid products are usually packaged in jars or tubes.

Semisolid products are usually packaged in jars or tubes.



Jars

Jars

 For extemporaneous packaging in a jar, use a

 For extemporaneous packaging in a jar, use a

flexible spatula and force the product down and along

flexible spatula and force the product down and along

the sides of the jar to avoid entrapping air.  On an

the sides of the jar to avoid entrapping air.  On an

industrial scale, a specified amount of the semisolid is

industrial scale, a specified amount of the semisolid is

forced into the jar with a pressure-filler.

forced into the jar with a pressure-filler.



Tubes

Tubes

  are also generally filled using a pressure-fill

  are also generally filled using a pressure-fill

technique and approaching the tube from the open

technique and approaching the tube from the open

back end (the end opposite from the cap).

back end (the end opposite from the cap).

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Topical dosage forms are expensive and it is important for you as a

pharmacist to council the patient to receive the maximum benefit.



Before application, cleanse the affected area and the healthy skin

surrounding it with soap and water unless otherwise directed by a

physician or by directions accompanying the medication.



Dry the cleansed area.



Topical should be applied as a thin film and spread evenly on the

skin.  Overuse, in general, is a waste of product.  When using a

solution, two or three drops should be placed on the area.



Gentle massaging after application of a topical may be advised to

cover the affected area.



Wash the medication off your hands with soap and water.



Occlusion of the affected area with a bandage or gauze is usually

not required and the medicated area should be left uncovered.

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