PubMed · 12092618
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2002. Capsule endoscopy.. https://pubmed.ncbi.nlm.nih.gov/12092618/
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Indium-111 is currently the radionuclide of choice for colonic transit study. However, it is expensive and not available in many hospitals. Technetium-99m has been proposed for colonic transit study but the short half-life has limited its use. Gallium-67 citrate is inexpensive and available in most countries. Most importantly, it has a suitable half-life for colonic transit study. Attempts have been made in some studies to use (67)Ga citrate to label activated charcoal, but the results have not been good because of poor stability. In this study, we successfully labelled activated charcoal()with (67)Ga citrate by adding alcohol and 5% glucose solution. To evaluate the in vitro stability, the (67)Ga-activated charcoal was incubated in a milieu mimicking the intestinal content, containing lipase, trypsin and glycochenodeoxycholate at different pH values (6.0, 7.0, 7.4 and 8.0) and for different durations (0 h, 24 h, 48 h, 72 h and 96 h). For the in vivo study, the (67)Ga-activated charcoal was loaded into a commercial empty enteric capsule. Colonic transit scintigraphy was performed in five volunteers, including three healthy people and two constipated patients, after intake of the radioactive capsule. Images were obtained at 2 h, 4 h, 6 h, 8 h, 24h, 48 h, 72 h etc. until no radioactivity was detected in the bowel. Our data show that the in vitro stability of (67)Ga-activated charcoal was good. The labelling efficiency still exceeded 91% at 96 h at pH values of 6.0, 7.0 and 7.4. In the group with a pH value of 8.0, the labelling efficiency gradually fell during the 4-day incubation but was still higher than 88% at the end of the fourth day. In the in vivo study, most capsules disintegrated in the caecum/colon region, and the (67)Ga-activated charcoal mixed very well with bowel content. In addition, the radioactive charcoal could be detected clearly on the 72-h image, which is very important for the evaluation of colonic transit time in patients with constipation. In conclusion, activated charcoal labelled with (67)Ga citrate is a potential radioactive marker for colonic transit study.
The applicability of pulsed field gradient nuclear magnetic resonance spectroscopy to nanocapsule systems is demonstrated on dispersed poly-n-butylcyanoacrylate nanocapsules as a model system. Spectroscopic data are presented that allow for the structural characterization of the inner cavities, the observation of Brownian motion of the capsules and the detection of rapid molecular exchange through the capsule walls. An analytical formula is proposed that yields equilibrium populations and average residence times of a given tracer molecule, thus leading to crucial information regarding the permeability of the capsule walls. Based on these analytical methods, two varieties of nanocapsules are compared that derive from two different preparation procedures. It is found that thinner capsule walls obtained under acidic conditions of the organic phase during interfacial polymerization lead to correspondingly higher exchange rates of benzene as a tracer molecule.
A novel pulsed-release system based on bilayer coated tablets containing an osmotically active agent is presented. Hydroxypropylmethylcellulose (HPMC) and the mixture of Eudragit RS and RL were applied as the swelling layer and semipermeable outer coat, respectively. To examine the mechanism of drug release from this pulsed-release system, drug release behaviors were investigated under conditions of various osmotic pressures. Both lag time and release rate were dependent on the coating level and the osmotic pressure of the dissolution medium. The swelling of tablets and the dynamics of water uptake during the dissolution were investigated to further elucidate the mechanism of drug release. The osmotic active agent induces a continuous water influx resulting in a rapid expansion of the membrane. The subsequent formation of fractures leads to a fast drug release after an initial lag time. All the results obtained in the present study indicated that both diffusion and osmotic pumping effect were involved in drug release from the device, but the latter was more dominant.