Background: The oral administration route is still the most preferred by patients for drug
treatment, but is unfortunately not suitable for all drug compounds. For example, protein and peptide
drugs (e.g. insulin) are typically administered via injection seeing as they are unstable in the gastrointestinal
luminal environment and have poor membrane permeation properties. To overcome this problem,
functional excipients such as drug absorption enhancers can be co-administered. Although Aloe vera gel
has the ability to improve the permeation of drugs across the intestinal epithelium, its drug permeation
enhancing effect has not been investigated in the different regions of the gastrointestinal tract yet.
Objective: The aim of this study was to investigate the insulin permeation enhancing effects of A. vera
gel material across excised pig intestinal tissues from different regions of the gastrointestinal tract and
to identify the gastrointestinal region where the highest insulin permeation enhancement was achieved.
Methods: Insulin transport across excised pig intestinal tissues from the duodenum, proximal jejunum,
medial jejunum, distal jejunum, ileum and colon was measured in the absence and presence of A. vera
gel (0.5% w/v) using both the Sweetana-Grass diffusion chamber and everted sac techniques.
Results: The insulin permeation results obtained from both ex vivo techniques showed varied permeation
enhancing effects of A. vera gel as a function of the different regions of the gastrointestinal tract.
The colon was identified as the gastrointestinal region where A. vera gel was the most effective in terms
of insulin permeation enhancement in the Sweetana-Grass diffusion chamber technique with a Papp
value of 5.50 x 10-7 cm.s-1, whereas the ileum was the region where the highest permeation enhancement
occurred in the everted sac technique with a Papp value of 5.45 x 10-7 cm.s-1.
Conclusion: The gastrointestinal permeation enhancing effects of A. vera gel on insulin is region specific
with the highest effect observed in the ileum and colon.