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Analysis of the meal-dependent intragastric performance of a gastric-retentive tablet assessed by magnetic resonance imaging (2003)

Steingoetter, A. ; Kunz, P. ; Weishaupt, D. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Alimentary pharmacology & therapeutics 18 (2003), S. 0

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ISSN: 1365-2036

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Medicine

Notes: Background : Modern medical imaging modalities can trace labelled oral drug dosage forms in the gastrointestinal tract, and thus represent important tools for the evaluation of their in vivo performance. The application of gastric-retentive drug delivery systems to improve bioavailability and to avoid unwanted plasma peak concentrations of orally administered drugs is of special interest in clinical and pharmaceutical research.Aim : To determine the influence of meal composition and timing of tablet administration on the intragastric performance of a gastric-retentive floating tablet using magnetic resonance imaging in the sitting position.Methods : A tablet formulation was labelled with iron oxide particles as negative magnetic resonance contrast marker to allow the monitoring of the tablet position in the food-filled human stomach. Labelled tablet was administered, together with three different solid meals, to volunteers seated in a 0.5-T open-configuration magnetic resonance system. Volunteers were followed over a 4-h period.Results : Labelled tablet was detectable in all subjects throughout the entire study. The tablet showed persistent good intragastric floating performance independent of meal composition. Unfavourable timing of tablet administration had a minor effect on the intragastric tablet residence time and floating performance.Conclusion : Magnetic resonance imaging can reliably monitor and analyse the in vivo performance of labelled gastric-retentive tablets in the human stomach.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2036.2003.01655.x

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Efficient three-step, two-color ionization of plutonium using a resonance enhanced 2-photon transition into an autoionizing state (2004)

Kunz, P. ; Huber, G. ; Passler, G. ; [et al.]

Springer

The European physical journal 29 (2004), S. 183-188

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ISSN: 1434-6079

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract. Resonance ionization mass spectrometry (RIMS) has proven to be a powerful method for isotope selective ultra-trace analysis of long-lived radioisotopes. For plutonium detection limits of $\rm 10^{6}$ to $\rm 10^{7}$ atoms have been achieved for various types of samples. So far a three-step, three-color laser excitation scheme was applied for efficient ionization. In this work, a two-photon transition from an excited state into a high-lying autoionizing state, will be presented, yielding a similar overall efficiency as the three-step, three-color ionization scheme. In this way, only two tunable lasers are needed, while the advantages of a three-step, three-color excitation (high selectivity, good efficiency and low non-resonant background) are preserved. The two-photon transition has been characterized with respect to saturation behavior and line width. The three-step, two-color ionization is a possibility for an improved RIMS procedure.