Ointments are the semi solid preparations intended for external use application on the skin and mucous membranes.
Ointments may b medicated or not. Unmedicated ointments are used for physical effects they provide as protectants, emollients, or lubricants.
Ointments bases may b used for their physical effect or as vehicles for medicated ointments.
OINTMENTS BASES:
Ointments bases are generally classified by the United States Pharmacopeia (USP) into four groups:
- Oleaginous bases
- Absorption bases
- Water-removable bases
- Water-soluble bases
Oleaginous bases:
They are also termed as hydrocarbon bases. on application to the skin, they have an emollient effect, protect against the escape of moisture, are effective as occlusive dressings, can remain on the skin for long periods without drying out, and, because of their immiscibility with water, are difficult to wash off.
Petrolatum, white petrolatum, white ointment, and yellow ointment are example of hydrocarbon ointment bases.
Absorption bases:
They are of two types:
- Those that permit the incorporation of aqueous solution resulting in the formation of water-in-oil(W/O) emulsion (e.g., hydrophilic petrolatum)and
- Those that are W/O emulsions that permit the incorporation of additional quantities of aqueous solutions (e.g., lanolin)
Hydrophilic petrolatum, USP and Lanolin, USP are the examples of absorption bases.
Water-removable bases:
They are oil-in-water emulsions commony called creams. Because the external phase of the emulsion is aqueous, they are easily washed from skin and are often called water-soluble bases.
Hydrophilic ointments, USP, is an example of this type of base.
Water-soluble bases:
Water-soluble bases don’t 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.
Polyethylene Glycol (PEG) Ointment, NF, is the prototype example of water-soluble base.
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