Shellac

Applications in Pharmaceutical Formulation or

Technology

Shellac is widely used as a moisture barrier coating for tablets and pellets due to its low water vapor and oxygen permeability. It has usually been applied in the form of alcoholic or aqueous solutions (pharmaceutical glazes). However, due to stability problems with

alcoholic shellac solutions, it has had limited use in the pharmaceutical industry for modified-release or enteric coatings; see also Shellac, particularly novel aqueous shellac solutions, is mainly used in food products and nutritional supplements. Recent research

results indicate good application properties and chemical stability of shellac films from aqueous shellac solutions. Aqueous ammonium shellac solutions, based on dewaxed orange shellac, do not show the problems exhibited by alcoholic shellac solutions

and are used as an enteric coating for pellets, tablets, soft and hard gelatine capsules, primarily in nutritional supplements. Shellac is a primary ingredient of pharmaceutical printing inks for capsules and tablets, and can be applied as a 40% w/v alcoholic

solution. It has also been used to apply one or two sealing coats to tablet cores to protect them from moisture before being film- or sugar-coated.

Other applications of shellac are the coating or encapsulation of powders or granules, e.g. in probiotics. Prior to the introduction of film coating, a combination of shellac, cetostearyl alcohol and stearic acid was used as an enteric coating. In cosmetics, shellac is

used in hairsprays, mascara and lipstick formulations. Aqueous shellac solutions are also used for colonic drug delivery.

Description

Shellac is a natural resin that may be obtained in a variety of colors ranging from light yellow to dark red in the form of hard, brittle flakes with or without wax, depending on the refining process; . The different types of shellac include bleached

shellac, bleached dewaxed shellac, dewaxed and decolorized shellac, dewaxed flake shellac, dewaxed orange shellac, dewaxed shellac, orange shellac, purified shellac, refined bleached shellac, regular bleached shellac, regular waxy shellac, wax-containing

shellac, and white shellac. The flakes may be crushed or milled to a coarse or fine powder. Bleached shellac is supplied as a coarse offwhite powder. Shellac is tasteless and may have a faint odor. The typical odor of shellac is the result of a complex fragrance system.