Cellulose acetate phthalate is a hygroscopic, white to off-white, freeflowing
powder, granule, or flake. It is tasteless and odorless, or
might have a slight odor of acetic acid.
Enteric coating in pharmaceutical products.
Cellulose acetate phthalate is produced by reacting the partial
acetate ester of cellulose with phthalic anhydride in the presence of a
tertiary organic base such as pyridine, or a strong acid such as
sulfuric acid.
Pharmaceutical Applications
Cellulose acetate phthalate (CAP) is used as an enteric film coating
material, or as a matrix binder for tablets and capsules. Such
coatings resist prolonged contact with the strongly acidic gastric
fluid, but dissolve in the mildly acidic or neutral intestinal
environment.
Cellulose acetate phthalate is commonly applied to solid-dosage
forms either by coating from organic or aqueous solvent systems, or
by direct compression. Concentrations generally used are 0.5–9.0%
of the core weight. The addition of plasticizers improves the water
resistance of this coating material, and formulations using such
plasticizers are more effective than when cellulose acetate phthalate
is used alone.
Cellulose acetate phthalate is compatible with many plasticizers,
including acetylated monoglyceride; butyl phthalybutyl glycolate;
dibutyl tartrate; diethyl phthalate; dimethyl phthalate; ethyl
phthalylethyl glycolate; glycerin; propylene glycol; triacetin; triacetin
citrate; and tripropionin. It is also used in combination with
other coating agents such as ethyl cellulose, in drug controlledrelease
preparations.
Therapeutically, cellulose acetate phthalate has recently been
reported to exhibit experimental microbicidal activity against
sexually transmitted disease pathogens, such as the HIV-1 retrovirus.
An experimental
teratogen. When heated to decomposition it
emits acrid smoke and irritating fumes.
Cellulose acetate phthalate is widely used in oral pharmaceutical
products and is generally regarded as a nontoxic material, free of
adverse effects.
Results of long-term feeding in rats and dogs have indicated a
low oral toxicity. Rats survived daily feedings of up to 30% in the
diet for up to 1 year without showing a depression in growth. Dogs
fed 16 g daily in the diet for 1 year remained normal.
Slow hydrolysis of cellulose acetate phthalate will occur under
prolonged adverse conditions such as high temperatures and high
humidity, with a resultant increase in free acid content, viscosity,
and odor of acetic acid. However, cellulose acetate phthalate is
stable if stored in a well-closed container in a cool, dry place.
Cellulose acetate phthalate is incompatible with ferrous sulfate,
ferric chloride, silver nitrate, sodium citrate, aluminum sulfate,
calcium chloride, mercuric chloride, barium nitrate, basic lead
acetate, and strong oxidizing agents such as strong alkalis and acids.
Included in the FDA Inactive Ingredients Database (oral tablets).
Included in nonparenteral medicines licensed in the UK. Included in
the Canadian List of Acceptable Non-medicinal Ingredients.
