Cellulose acetate phthalate (
CAP), also known as
cellacefate and
cellulosi acetas phthalas, is a commonly used
polymer phthalate in the formulation of
pharmaceuticals, such as the
enteric coating of
tablets or
capsules and for
controlled release formulations. It is a
cellulose polymer where about half of the
hydroxyls are esterified with
acetyls, a quarter are esterified with one or two carboxyls of a
phthalic acid, and the remainder are unchanged. Its
CAS number is [9004-38-0]. It is a hygroscopic white to off-white free-flowing powder, granules, or flakes. It is tasteless and odorless, though may have a weak odor of
acetic acid. Its main use in pharmaceutics is with
enteric formulations. It can be used together with other coating agents, e.g.
ethyl cellulose. Cellulose acetate phthalate is commonly
plasticized with
diethyl phthalate, a
hydrophobic compound, or
triethyl citrate, a
hydrophilic compound; other compatible plasticizers are various phthalates,
triacetin, dibutyl tartrate,
glycerol,
propylene glycol, tripropionin, triacetin citrate, acetylated monoglycerides, etc.