(4) Summary of oleaginous bases. We can sum up the oleaginous ointment
bases as follows:
(a) Properties. Not good water absorbers, insoluble in water, not
washable, not greasy.
(b) Examples. Fats and fixed oils such as lard olive oil, cottonseed oil,
petrolatum, white ointment, plastibase, and silicon bases.
Advantages. Highly compatible; all but the fats and oils are stable;
(d) Disadvantages. Difficult to remove from skin and clothing;
uncertain as to yield of medicament.
b. Absorption Bases. An absorption base absorbs water or aqueous solutions
of medicinals. These bases are generally anhydrous (waterless), hydrophilic (water
(1) Constituents. The most common absorption bases are composed of
petrolatum mixed with animal sterols such as cholesterol. Aquaphor is a widely used
and excellent example of an absorption base. Hydrophilic Petrolatum, USP is another.
Summary of absorption bases. We can sum up the absorption bases as
(a) Properties. Anhydrous; will absorb water; most are not washable.
Example. Hydropholic Petrolatum, USP; aquaphor; Anhydrous
(c) Advantages. Highly compatible; relatively stable to heat; can be
used in anhydrous form or water can be added when emolliency is desired.
c. Emulsion Bases. Emulsion ointment bases consist of an aqueous phase, an
oleaginous phase, and an emulsifying agent. They are true, solid emulsions. Emulsion
bases may be either oil-in-water (o/w) or water-in-oil (w/o), usually depending upon the
phase in which the emulsifier is more soluble. The water phase varies from 10 percent
to 80 percent of the completed ointment base.