Properties of ideal ointment base: 1- inert
2- stable
3- smooth
4- compatible with the skin
5-non irritating
6- easily release the incorporated medicament
Classification of ointment bases: Ointment bases are divided into four types:1- oleaginous bases
2- absorption bases
3- emulsion bases (w/o, o/w)
4- water-miscible bases
1-Oleaginous bases:
- Consist of water insoluble hydrophobic oils and fats such as mineral oil, petrolatum, paraffins and lards
- Combination of these materials can produce ointment which have the desired melting and viscosity.
Disadvantages: 1- greasy
2- difficult to be removed from skin and from clothes
3-the release of medicament is not certain
4- they may get rancid
5- prevent the drainage on oozing area and prevent evaporation of cautaneous secretion. The water retention increases the heat in certain areas
I -Ingredients Petrolatum (Soft paraffin): Mixture of semisolid hydrocarbons obtained from petroleum; there is two types: yellow soft paraffin
A-Pale yellow to yellow translucent mass free from odour and taste, m.p 38-56 ºC. white soft paraffin
B -Obtained by bleaching of yellow soft paraffin. Used when the medicament is white or colorless.
II- Hard paraffin: Solid hydrocarbons obtained by distallation of petroleum, white, odorless, tasteless.
- Used to harden or stiffen the ointment base.
III -Liquid paraffin: It is known as liquid petroleum or white mineral oil, consists of a mixture of liquid hydrocarbons. It is colorless, tasteless and odorless oily liquid. Insoluble in water and alcohol but soluble in ether and chloroform.
- Used with hard and soft paraffins to obtain ointment of desired viscosity. It is also used to levigate substances insoluble on it.
IV -Microcrystalline wax: It is a mixture of saturated alkanes, They have greater stability to the ointments.
- Combination of these materials can produce ointment which have the desired melting and viscosity.
Disadvantages: 1- greasy
2- difficult to be removed from skin and from clothes
3-the release of medicament is not certain
4- they may get rancid
5- prevent the drainage on oozing area and prevent evaporation of cautaneous secretion. The water retention increases the heat in certain areas
I -Ingredients Petrolatum (Soft paraffin): Mixture of semisolid hydrocarbons obtained from petroleum; there is two types: yellow soft paraffin
A-Pale yellow to yellow translucent mass free from odour and taste, m.p 38-56 ºC. white soft paraffin
B -Obtained by bleaching of yellow soft paraffin. Used when the medicament is white or colorless.
II- Hard paraffin: Solid hydrocarbons obtained by distallation of petroleum, white, odorless, tasteless.
- Used to harden or stiffen the ointment base.
III -Liquid paraffin: It is known as liquid petroleum or white mineral oil, consists of a mixture of liquid hydrocarbons. It is colorless, tasteless and odorless oily liquid. Insoluble in water and alcohol but soluble in ether and chloroform.
- Used with hard and soft paraffins to obtain ointment of desired viscosity. It is also used to levigate substances insoluble on it.
IV -Microcrystalline wax: It is a mixture of saturated alkanes, They have greater stability to the ointments.
2-Absorption bases: Hydrophilic anhydrous bases which can absorb large amount of water but still retain ointment like consistency and still difficult to remove by wash.
Types of absorption base:
- Non-emulsified bases such as:
1-Anhydrous wool fat (anhydrous lanoline): Anhydrous fat obtained from the wool of sheep, practically insoluble in water but can absorb about 50% of water. So it is used in ointment where the amount of water or aqueous solution to be incorporated in is too large.
2- Hydrous wool fat (lanoline): Yellowish ointment fat substance with characteristic odor obtained from wool sheep. Insoluble in water but soluble in ether and chloroform.
- Mixture of 70% w/w wool fat and 30% w/w water, water in oil emulsion aqueous liquid can be emulsified with it.
3- Wool alcohol: Obtained by treating wool with alkali and separating the fraction containing cholesterol and other alcohols. Contain less than 30% cholesterol.
- Used as emulsifying agents for preparation of w/o emulsion and to absorb water in ointment bases. It also used to improve the texture, stability and emollient properties of oil in water emulsion.
4- Bees wax, Wax obtained from the honeycomb of bees and it is of two types:
a- Yellow bees was
b- white bees wax obtained by bleaching of yellow bees wax.
- Used as stiffening agents pastes, ointments and other preparation.
5- Cholesterol: Widely distributed in animal organisms, used to increase the incorporation of aqueous substances in oils and fats.
Advantages of Absorption bases:
1-compatible with majority of medicaments
2-relatively heat stable
3-used in both anhydrous form and emulsified form
4-absorb large quantity of water or aqueous substances
3-Emulsion Bases= miscible or removable bases.
- Semisolid emulsion having cream like consistency. There are two types; oil in water or water in oil emulsions
- The oil in water base is more popular than water in oil because they can be easily removed from the skin and clothes. In contrast the water in oil bases are more greasy and difficult to be removed from the skin and clothes.
b- white bees wax obtained by bleaching of yellow bees wax.
- Used as stiffening agents pastes, ointments and other preparation.
5- Cholesterol: Widely distributed in animal organisms, used to increase the incorporation of aqueous substances in oils and fats.
Advantages of Absorption bases:
1-compatible with majority of medicaments
2-relatively heat stable
3-used in both anhydrous form and emulsified form
4-absorb large quantity of water or aqueous substances
3-Emulsion Bases= miscible or removable bases.
- Semisolid emulsion having cream like consistency. There are two types; oil in water or water in oil emulsions
- The oil in water base is more popular than water in oil because they can be easily removed from the skin and clothes. In contrast the water in oil bases are more greasy and difficult to be removed from the skin and clothes.
