Looking for Information on Ointments? Here’s the Complete Classification Explained

Ointments are smooth and semi-solid substances designed for applying externally to the skin or mucous membranes. It is usually a drug or drugs that are dissolved, suspended or emulsified in a base.

Ointments are used on the skin to reduce inflammation and have a protective action. In addition, they have applications in vehicles as well.

Characteristics of an ideal ointment :-

• It should be smooth and free form micro-organism.
• The foundation should be non-irritating and free from any therapeutic effects.
• It should also exhibit stability in terms of its chemical and physical properties.
• It should melt or soften at body temperature and be easily applied.

Classification of ointments :-

1. According to therapeutic properties based on penetration.
2. According to their therapeutic uses.

1) According to therapeutic properties based on penetration :-

• Epidermic ointment
• Endodermic ointment
• Diadermic ointment

1) Epidermic ointment :-

These ointments aim to produce a local effect by acting directly on the surface of the skin. They are not absorbed. These ointments act as protectives, antiseptics, local anti infectives and povidone iodine.

2) Endo dermic ointments :-

The purpose of these ointments is to deliver medications that can deeply penetrate the skin. They are absorbed and act as emollients, stimulants and local irritants. Eg- Diclofenac sodium ointment or soften.

3) Diadermic ointment :-

These ointment are intended to release the medicaments that pass through the skin and produce systemic effects.

ex. voveran

2) According to their therapeutic uses –

a) Antibiotic ointments :-

These ointments are used to kill the micro-organisms. They agents used are bacitracin, chlortetracycline, neomycin, quaternary ammonium compounds etc.

b) Anti-inflammatory ointments :-

These ointment are used to relieve inflammatory, allergic and pruritic conditions of the skin.

ex.- Betamethason

c) Anti- fungal ointments :-

These ointment are used to inhibit or kill the fungi. Ex.- benzoic acid, salicylic acid, nystatin etc.

d) Antipruritic ointment :- These ointments are used to relieve itching. ex.- benzocaine

e) Astringent ointments :- These ointments used to contraction of the skin and decrease discharges. ex.- calamine and zinc oxide

f) Emollient ointment :- These preparations which are used to soften the skin. is.- soft paraffin and cold cream.

Ointment Bases :-

The ointment base is that substance or part of an ointment which is a vehicle for the medicament.

An ideal ointment bases should be inert, stable, smooth, with the skin, non-irritating and should release the incorporated medicament.

These is no single ointment base available which possesses all these qualities, therefore it becomes necessary to use more than one ointment base in the preparation of ointments.

Classification of ointment bases :-

1. Oleaginous bases
2. Absorption bases
3. Emulsion bases
4. Water soluble bases

a) Oleaginous bases :-

These bases consist of water insoluble and fats. The most important are the hydrocarbons. ex. Mineral oils, petrolatums and paraffins.

When these materials are combined, the resulting product can possess the desired melting point and viscosity.

Soft paraffin :-

It is a purified mixture of semisolid hydrocarbon obtained from petroleum. The soft paraffin available in two forms.

Hard paraffin :-

It is a purified mixture of solid hydrocarbons obtained by distillation form petroleum. It is a colourless or white, odourless, tasteless mass and it is used to harden or the ointment bases.

Liquid paraffin :-

The liquid paraffin is also known as liquid petrolatum or white mineral oil. It is consist of a mixture of liquid hydrocarbons may be obtained from petroleum by distillation.

b) Absorption bases :-

Absorption is the term used to denote the base’s hydrophilic characteristics. These are generally anhydrous base which can absorb a large amount of water but still retain their ointment. like – consistency

1) Wool fat :-

It is also known as anhydrous lanolin. Lanolin, obtained from sheep’s wool, is a purified and moisture-free fat-like substance.

2) Hydrous wool fat :-

It is also known as lanolin. Lanolin is the refined fatty substance extracted from sheep’s wool. It has a yellowish-white appearance and emits a characteristic scent. It is insoluble in ether and chloroform.

3) Cholesterol :-

It is widely distributed in animal organisms. Cholesterol can be derived from wool fat as well. It is used to increase the incorporation of aqueous substance in oils and fats.

Advantages of Absorption Bases :-

1. They are compatible with majority of medicaments.

2. They are heat stable.

3. These bases may be used in their anhydrous from or in emulsified from.

4. They can absorb a large quantity of water.

Disadvantages:-

These bases possess the undesirable property of ointments but they can be more easily removed from the skin as compared to the oily bases.

c) Emulsion Bases :-

These bases are semisolid emulsion have like cream. These bases are two types:-

1. oil in water
2. water in oil

some additional amount of water can be incorporated in both type of bases are more popular because they can be easily removed from the skin. The water in oil emulsion based are difficult to removed from the body. ex.- hydrophilic ointment and rose water ointment.

d) Water soluble bases :-

This bases contain only the water soluble ingredient and not the fats and other substance. It is consist of water soluble ingredients such as polyethylene glycol, polymers.

Which are known as carbo waxes they do not hydrolyses and do not support the bacterial growth. The certain substances which are used as water soluble bases include tragacanth, gelatin etc.

Preparation of ointments :-

The two methods of preparation of ointments are generally used-

1. Trituration method
2. Fusion method

1. Trituration method :-

This is the method most commonly used for the preparation of ointments. the medicaments which are to be incorporated in the base are generally insoluble. Therefore it becomes necessary to reduce the medicament to fine powder. in the method of trituration with a small amount of the base on an ointment slab with the help of stainless steel spatula with long broad blade.

2. Fusion method :-

When an ointment base contains a number of solid ingredients such as white beeswax, cetyl alcohol, and hard paraffin as the components of the base.

Stability of ointments :-

1. The ointment should be stable from the time of preparation to the time when whole of it is consumed.
2. The long storage of the ointments lead to microbial growth.
3. It is a suitable preservative must be added to inhibit the growth of contaminating micro organisms.
4. They should not react with the components of the formulation as well as the containers.
5. The commonly used preservatives for ointments include phenol, benzoic acid etc.