Gastrointestinal release site for delayed release and gelatin capsules in healthy dogs

Gelatin capsules deliver their contents to the stomach, while delayed-release (DR) capsules are designed to allow delivery to the small intestine. This study evaluated the gastrointestinal release site of DR capsules in six healthy adult dogs compared to gelatin capsules. Both gelatin and DR capsules were filled with barium-impregnated polyethylene spheres (BIPS™), and following enteral administration, release site was assessed using abdominal radiographs at baseline, immediately after ingestion, 15 min post-ingestion, 30 min post-ingestion, and then every 30 min thereafter. The evaluated phases included fasted conditions (phase 1, n = 6), increased meal size (phase 2, n = 2), double encapsulation (phase 3, n = 2), and altered capsule size (phase 4, n = 1). The released site was the stomach in all phases for both capsule types. In phase 1, DR capsules had a significantly prolonged time (median 60 min, range 60-90) to release BIPS™ compared to gelatin capsules (15 min, range 15-30; p = .03). In phase 2 (full meal size), 3 (double encapsulation), and 4 (smaller capsule size) pilot studies, release time was prolonged but still occurred in the stomach. This is similar to the release site for gelatin capsules but differs from the release site for DR capsules in people. This has implications for pharmacologic outcomes for products that are affected by gastric physiology (e.g. fecal microbiota transplantation). Based on this pilot data, clinicians and researchers should not assume DR capsules will allow for intestinal delivery of contents in dogs. Future studies should be conducted on larger and varied populations of dogs.