Chemical Properties
Microcrystalline wax occurs as odorless and tasteless waxy lumps
or flakes containing small irregularly shaped crystals. It may vary in
color from white to yellow, amber, brown, or black depending on
the grade of material; pharmaceutical grades are usually white or
yellow.
The USP32–NF27 describes microcrystalline wax as a mixture
of straight-chain, branched-chain, and cyclic hydrocarbons,
obtained by solvent fractionation of the still-bottom fraction of
petroleum by suitable means of dewaxing or de-oiling.
Definition
MICROCRYSTALLINE WAX is a complex combination of long, branched chain hydrocarbons obtained from residual oils by solvent crystallization. It consists predominantly of saturated straight and branched chain hydrocarbons predominantly greater than C35.
Production Methods
Microcrystalline wax is obtained by solvent fractionation of the
still-bottom fraction of petroleum by suitable dewaxing or deoiling.
Flammability and Explosibility
Notclassified
Pharmaceutical Applications
Microcrystalline wax is used mainly as a stiffening agent in topical
creams and ointments.
The wax is used to modify the crystal structure of other waxes
(particularly paraffin wax) present in a mixture so that changes in crystal structure, usually exhibited over a period of time, do not
occur. Microcrystalline wax also minimizes the sweating or bleeding
of oils from blends of oils and waxes. Microcrystalline wax
generally has a higher melting point than paraffin wax, and higher
viscosity when molten, thereby increasing the consistency of creams
and ointments when incorporated into such formulations.
Microcrystalline wax is also used in oral controlled-release
matrix pellet formulations for various active compounds and as
a tablet- and capsule-coating agent. In controlled-release systems,
microcrystalline wax coatings can also be used to affect the release
of drug from ion-exchange resin beads.
Microcrystalline wax is also used in confectionery, cosmetics,
and food products.
Safety
Microcrystalline wax is mainly used in topical pharmaceutical
formulations but is also used in some oral products. It is generally
regarded as a nontoxic and nonirritating material.
storage
Microcrystalline wax is stable in the presence of acids, alkalis, light,
and air. The bulk material should be stored in a well-closed
container in a cool, dry place.
Regulatory Status
GRAS listed. Accepted for use as a food additive in Europe.
Included in the FDA Inactive Ingredients Database (oral capsules;
topical and vaginal preparations). Included in nonparenteral
medicines licensed in the UK. Included in the Canadian List of
Acceptable Non-medicinal Ingredients.
