The aim of this study was to develop a multiple-unit dosage system that released model drug into the colon, and also to evaluate the efficiency of the dosage form in human volunteers. The developed system combines pH-, time- and biodegradable polymer-based mechanisms for drug targeting to the colon. Pellet cores containing caffeine as model drug and chitosan and microcrystalline cellulose as excipients were prepared by the extrusion/spheronization method. The prepared pellets were film coated with a pH-dependent polymer, Eudragit FS 30 D. The coating total weight gain was 28.83% (w/w). Thanks to the application of an outer enteric film and the multiple unit design of the dosage form, the variability in gastric emptying was overcome, and a colon-specific targeting relied on the reproducibility of a small intestinal transit time, which was reported to be 3 ± 1 hours. A biodegradable polymer in the pellet core, chitosan, ensured the site-specific release of the model drug due to its solubility at the lower pH of the colonic region and by its biodegradability from the bacteria present. The efficiency of the system was confirmed by the in vivo testing of human saliva. The time of the first appearance of caffeine into the saliva, T(lag), was used as a parameter to estimate the disintegration time of the pellets into the gastrointestinal tract. The caffeine appeared in the saliva within 6.95 ± 1.12 hours (T(lag)) in 9 volunteers. A comparison of the reported colon arrival times indicates that the developed system is applicable to colonic drug delivery.

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