Concentration and surface of absorption: Concepts and applications to gastrointestinal patches delivery

Gastrointestinal patches represent a novel multiparticulate drug delivery system able to increase the intestinal absorption of drugs with poor bioavailability. The number of patches to administer is a critical issue since it is related to the surface and drug concentration at the absorption site.The objective of this article is to evaluate the effect of the number of administered patches on the final absorption of leuprolide, a peptide chosen as model drug, assuming complete adhesion of all the devices to the intestinal membrane.The same dose of leuprolide was encapsulated into 2, 4 and 6 patches; the resulting intestinal absorption profiles were measured with the Ussing chamber ex vivo experimental setup and compared between them.The results showed that varying the number of patches, the final absorption does not present statistically significant changes, indicating that changes in concentration are balanced by change in absorption surface. These experimental findings can also be explained considering the equation that links the drug flow to surface and concentration at the absorption site, showing that the drug flow is related only to the geometry of each individual patch.

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