Colon delivery systems for oral administration have grown in popularity since the 1990s, primarily because of the increasing incidence of inflammatory bowel disease (IBD) that has broadly been demonstrated to benefit from topical pharmacological treatment. Moreover, selective release of biotechnological drugs to the large bowel has been proposed as a viable strategy to have their oral bioavailability enhanced with respect to gastric and/or small intestinal delivery as yielded by conventional peroral dosage forms.

So far, a wide range of targeting formulation approaches have been explored, which are generally based on physioloical parameters typically differing between the large bowel and more proximal regions of the digestive tract. Enteric coated systems, in particular, are intended to pursue colon delivery by exploiting differences in the pH of gastrointestinal fluids. Polymethacrylates with a pH-dependent dissolution threshold ranging from pH 6.0 to 7.0 are mainly used as coat- ing agents aimed at protecting the drug core from gastric and small intestinal contents, Eudragit® S (EuS), Eudragit® L (EuL), and Eudragit® FS (EuFS) (Evonik Industries) being popular brands thereof [5]. This is notably the formulation strategy behind most of anti-inflammatory drug products that are commercially available worldwide for the therapy of ulcerative colitis and Crohn’s disease (IBD).

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