Evaluation of the Intelisite capsule to deliver theophylline and frusemide tablets to the small intestine and colon.

The objective of the research was to establish the capability of the Intelisite capsule to deliver the probe drugs, theophylline and frusemide, in the form of split immediate release (IR) tablets, to the small intestine and colon. The two probe drugs were administered together in an open, random, three-way crossover study in eight healthy volunteers, comparing absorption following Intelisite delivery in the small bowel and colon to conventional IR dosing. Gamma scintigraphy was employed to monitor the gastrointestinal transit and activation of the Intelisite capsule. Standard pharmacokinetic parameters, and the percentage remaining in the capsules post defecation were determined. The Intelisite capsule was well tolerated in human volunteers and successfully activated on 15/16 occasions. Pharmacoscintigraphy showed internal marker release from the Intelisite capsule to be approximately 10-fold faster in the small intestine than in the colon. Theophylline and frusemide were both well absorbed following Intelisite activation in the small intestine, whereas complete colonic absorption was only observed in 1/7 subjects for theophylline, and 0/7 subjects for frusemide. The probe drugs were successfully delivered in particulate form from the Intelisite capsule in the small intestine and produced expected pharmacokinetic profiles. However drug release in the colon was incomplete and variable possibly due to: low water content, poor mixing, and a high loading dose.

Epi-fluorescence microscopy and image analysis used to measure diffusion coefficients in gel systems.

A method using epi-fluorescence microscopy and image analysis has been developed to follow and quantify the diffusion of fluorescent compounds through gels. Two mathematical approaches were employed to calculate diffusion coefficients. The spatial resolution provided by the fluorescence microscope allowed diffusion to be followed over very short distances; accordingly diffusion coefficients were obtained within minutes, even for slowly diffusing systems. The method was successfully applied to the diffusion of macromolecules into agar, carbopol and mucus gel systems.