F. Raffin et al., PHYSICOCHEMICAL CHARACTERIZATION OF THE IONIC PERMEABILITY OF AN ENTERIC COATING POLYMER, International journal of pharmaceutics, 120(2), 1995, pp. 205-214
Cellulose acetate phthalate (CAP) is widely used as an enteric coating
polymer. In this work, radiotracer and impedance measurements were pe
rformed in order to study the evolution in time of CAP films immersed
in different solutions including artificial gastric juice. The membran
e permeabilities demonstrate a strong dependence on the pH value, sugg
esting our film to behave like a cation-exchange membrane. A two-step
transport mechanism is proposed to explain the variation of the experi
mental data with time. The effects of different plasticizers and solve
nts were also investigated, our observations showing the importance of
using a hydrophobic plasticizer to improve the gastroresistance of th
e polymer.