Reproducibility of neutron activated Sm-153 oral dose formulations intended for human administration

Colonic delivery of metronidazole-loaded capsules for local treatment of bacterial infections: A clinical pharmacoscintigraphy study

Drug delivery to the colon offers great promise for local treatment of colonic diseases as it allows bypassing systemic absorption in the small intestine, thereby increasing luminal drug concentrations in the colon. The primary objective of this in vivo pharmaco-scintigraphy study was to assess the colon drug targeting accuracy of a metronidazole benzoate colonic drug delivery system intended for local treatment of Clostridioides difficile infections. Additionally, it was assessed if the concept of mucoadhesion would increase colonic residence time and promote higher drug bioavailability. Two different capsule formulations were designed and tested in healthy human subjects. Capsules contained either non-mucoadhesive (NM) or mucoadhesive (M) microgranules, both loaded with 100 mg metronidazole benzoate (antibiotic prodrug) and 5 mg samarium oxide (scintigraphy tracer). Filled capsules were coated with a colonic-targeting technology consisting of two functional layers, which allow for accelerated drug release mediated by the intestinal pH in combination with colonic bacteria. Coated capsules were neutron-activated to yield the radioisotope ¹⁵³Sm prior to administration to 18 healthy subjects. Gamma-scintigraphy imaging was combined with the measurement of drug plasma levels. Formulation NM showed high colon-targeting accuracy. Initial capsule disintegration within the targeted ileocolonic region was observed in 8 out of 9 subjects (89%) with colonic arrival times in the range of 3.5-12 h and reduced systemic exposure. In contrast, the mucoadhesive formulation M showed some inconsistency regarding the site of initial capsule disintegration (targeting accuracy 56%). Variability of drug release was attributed to self-adhesion and agglomeration of the mucoadhesive microparticles within the capsule. Accurate ileocolonic delivery of metronidazole-loaded microgranules was achieved following oral administration of colonic-targeted capsules. Delayed drug release from NM microparticles in the colon leads to a reduced systemic exposure compared to immediate-release data from literature and presumably elevated drug concentrations in the colonic lumen. This approach offers promising options for the local treatment of colonic diseases.

99mTc-MDP as an imaging tool to evaluate the in vivo biodistribution of solid lipid nanoparticles

The aim of this study was to establish the in vivo uptake and tissue distribution of ^99mTc-MDP-encapsulated Solid Lipid Nanoparticles (SLNs) post administration. Radioactive ^99mTc-MDP encapsulated into SLNs was administered to rats to trace their biodistribution through imaging and ex vivo studies. As expected IV injected ^99mTc-MDP exhibited predominant visual bone uptake and a high localisation of particles in the kidneys (3.87%ID/g) followed by bone (2.66%ID/g). IV administered ^99mTc-MDP encapsulated by SLN showed similar uptake than ^99mTc-MDP. Orally administrated ^99mTc-MDP showed no uptake in any organs except the GI-tract while orally administered ^99mTc-MDP-SLN showed distinct transfer of ^99mTc-MDP from the GI tract with measurable levels in the kidneys and bone.

Production and first use of 153SmCl3-ion exchange resin capsule formulation for assessing gastrointestinal motility

We produced an enteric-coated gelatine capsule containing neutron-activated (153)Sm-labelled resin beads for use in gastrointestinal motility studies. In vitro test in simulated gastrointestinal environment and in vivo study on volunteers were performed. Scintigraphic images were acquired from ten volunteers over 24h while blood and urine samples were collected to monitor the presence of (153)Sm. All the capsules remained intact in stomach. This proved to be a safe and practical oral capsule formulation for whole gut transit scintigraphy.