Oral ileocolonic drug delivery by the colopulse-system: a bioavailability study in healthy volunteers.

The release profile of a novel oral ileocolonic drug delivery technology (ColoPulse-technology) was assessed by a combination of conventional kinetics of a marker substance in blood and site-specific signaling by stable isotope technology. Since ileocolonic delivery involves the drug release in a region in which bacteria are highly present, a prolonged lag time should coincide with proven bacterial enzyme activity. The latter can be tested using 13C-urea as the marker substance. The study was designed as a two period (uncoated versus coated capsule) crossover single dose bioavailability study in healthy subjects. The 13C-recovery data after oral administration of 13C-urea using the ColoPulse delivery system showed a delayed sigmoid release in all subjects with a lag time of > 3h (median: 330 min). Release was achieved in a urease-containing intestinal segment in all healthy subjects. Complete release in the ileocolonic region was achieved in 10 of 11 subjects. The ColoPulse-technology therefore enables specific and reliable drug delivery in the ileocolonic region in healthy volunteers.

Proof-of-concept study on the suitability of 13C-urea as a marker substance for assessment of in vivo behaviour of oral colon-targeted dosage forms.

BACKGROUND AND PURPOSE: (13)C-urea may be a suitable marker to assess the in vivo fate of colon-targeted dosage forms given by mouth. We postulated that release in the colon (urease-rich segment) of (13)C-urea from colon-targeted capsules would lead to fermentation of (13)C-urea by bacterial ureases into (13)CO(2). Subsequent absorption into the blood and circulation would lead to detectable (13)C (as (13)CO(2)) in breath. If, however, release of (13)C-urea occurred in the small intestine (urease-poor segment), we expected detectable (13)C (as (13)C-urea) in blood but no breath (13)C (as (13)CO(2)). The differential kinetics of (13)C-urea could thus potentially describe both release kinetics and indicate the gastrointestinal segment of release. EXPERIMENTAL APPROACH: The in vivo study consisted of three experiments, during which the same group of four volunteers participated. KEY RESULTS: The kinetic model was internally valid. The appearance of (13)C-in breath CO(2) (F(fermented)) and the appearance of (13)C in blood as (13)C-urea (F(not fermented)) show a high inverse correlation (Pearson's r=-0.981, P= 0.06). The total recovery of (13)C (F(fermented)+F(not fermented)) averaged 99%, indicating complete recovery of the administered (13)C via breath and blood. (13)CO(2) exhalation was observed in all subjects. This indicates that (13)C-urea was available in urease-rich segments, such as the caecum or colon. CONCLUSIONS AND IMPLICATIONS: In this proof-of-concept study, (13)C-urea was able to provide information on both the release kinetics of a colon-targeted oral dosage form and the gastrointestinal segment where it was released.