Pharmaceutical Manufacturing Handbook: Production and

OINTMENTS AND CREAMS 271
compendial status, synonym, and specifi cations of some of the bases used in ointments
and creams.
The following sections describe the source, physicochemical properties, formulation
considerations, stability, incompatibility, storage, and hypersensitivity reactions
of some of these bases.
Lanolin Lanolin is a refi ned, decolorized, and deodorized material obtained from
sheep wool. It is available as a pale yellow, waxy material with a characteristic odor.
It is extensively used in the preparation of hydrophobic ointments and water - in - oil
creams. As lanolin is prone to oxidation, antioxidants such as butylated hydroxytoluene
are generally included. Although lanolin is insoluble in water, it is miscible
with water up to 1 : 2 ratio. This property favors in preparing physically stable creams.
Addition of soft paraffi n or vegetable oil improves the emollient property of lanolin
preparations. Exposure of lanolin to higher temperature usually leads to discoloration
and rancidlike odor, and hence prolonged heating is avoided during the
preparation and preservation of lanolin - containing preparations. Gamma sterilization
or fi ltration sterilization is usually employed for sterilizing ophthalmic ointments
containing lanolin. Lanolin and some of its derivatives are reported to cause
hypersensitivity reactions and therefore are avoided in patients with known hypersensitivity.
One of the reasons for hypersensitivity reactions is free fatty alcohols.
Modifi ed lanolins containing reduced levels of free fatty alcohols are commercially
available [2, 3] .
Hydrous Lanolin Incorporation of about 25 – 30% of water into lanolin gives
hydrous lanolin. Gradual addition of water into molten lanolin with constant stirring
helps in water incorporation. It is available as a pale yellow, oily material with a
characteristic odor. The water uptake capacity of hydrous lanolin is higher than
lanolin, and it is used for preparing topical hydrophobic ointments or water - in - oil
creams with larger aqueous phase. Exposure of these preparations to higher temperatures
results in separations of oily and aqueous layers. Addition of antioxidants
and preservation in well - fi lled, airtight, light - resistant containers in a cool and dry
place improve the stability of lanolin products. Well - preserved preparations can be
stored up to two years. Hydrous lanolin that contains free fatty alcohols is avoided
in hypersensitive patients [2, 3] .
Lanolin Alcohols Lanolin alcohol is prepared from lanolin by the saponifi cation
process and is used as a hydrophobic vehicle in pharmaceutical ointments and
creams. It is composed of steroidal and triterpene alcohols and is available as a
brittle solid material pale yellow in color with a faint characteristic odor. The brittle
powder becomes plastic under warm conditions. It is practically insoluble in water
and soluble in boiling ethanol. Lanolin alcohol possesses emollient properties, which
makes it suitable for preparing dry - skin ointments, eye ointments, and water - in - oil
creams. Creams containing lanolin alcohols do not show surface darkening and
do not produce objectionable odor compared to lanolin - containing preparations.
Inclusion of about 0.1% antioxidant, however, minimizes the oxidation on storage.
Preparations containing lanolin alcohols can be stored up to two years if preserved
in well - fi lled, well - closed, light - resistant containers in a cool and dry place. As with