Polymer film formulations for the preparation of enteric pharmaceutical capsules

Objectives
Standard pharmaceutical capsules are designed to dissolve in the acidic environment of the stomach releasing the encapsulated contents for absorption. When release is required further along the gastrointestinal tract capsules can be coated with acid insoluble polymers to enable passage through the stomach and dissolution in the intestine. This paper describes formulations that have the potential to be used to produce two-piece hard capsules for post-gastric delivery without the requirement of an exterior coat.
Methods
The formulation uses three polysaccharides: sodium alginate, hypromellose and gellan gum to provide acid insolubility and the ability to form a capsule using standard industrial equipment.
Key findings
The rheological profile on cooling, of the base material, water content and thickness of the films were shown to be comparable with those of commercial capsules. The capsules remained intact for 2 h in 100 mM HCl at pH 1.2 and within 5 min of being removed from the acid and submerged in phosphate-buffered saline at pH 6.8 were
ruptured.
Conclusions
Selected formulations from this study have potential for use as delayed release capsules.