Cellulose acetate phthalate

Cellulose acetate phthalate (CAP), a pharmaceutical excipient used for enteric film coating of capsules and tablets

Cellulose acetate phthalate is used as an enteric film-coating material, as a microencapsulation agent, or as a matrix binder for

tablets and capsules.(1–8) 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 controlled-release preparations.