1,720,957 research outputs found
Design, development and bioavailability assessment of oxytetracycline hydrochloride double O/W/O microemulsion formulation
No full textThe aim of this research was to improve the oral bioavailability of oxytetracycline hydrochloride,a broad spectrum antibiotic having poor oral bioavailability,through the formulation of double o/w/o microemulsion systems. The range of compositions forming a clear one-phase region (primary o/w microemulsion) was evaluated through the construction of the ternary diagram and then three different types of double microemulsions were prepared using the “two-step technology”. The formulations were characterized for droplet size and zeta potential. DSC was used for determining the type of microemulsion and to verify the formation of double microemulsion systems. The physical characterization gave satisfactory results that were compatible with double microemulsion systems. Finally,the pharmacokinetics of microemulsions was evaluated after oral administration on rats and compared to that of an aqueous and an oily solution. Results indicated an oral bioavailability enhancement of 5.7 and 2 times over the aqueous and oily solutions,respectively
Development and pharmacokinetic evaluation of erythromycin lipidic formulations for oral administration in rainbow trout (Oncorhynchus mykiss)
No full textThe aim of this work was to enhance the bioavailability of erythromycin base when administered orally
in rainbow trout (Oncorhynchus mykiss). Since erythromycin is normally given in the form of medicated
feed, in this study three new types of feed formulation were developed. A self-emulsifying system and
two types of double microemulsions (O/W/O) were prepared, characterized and adsorbed on a commercial
extruded diet for fish. The emulsified systems were based on saturated polyglycolized glycerides and
mono- and diglycerides of medium-chain fatty acids (as oily phase), Tween 80 (as surfactant) and, in the
case of double microemulsions, distilled water. The systems differed in percentage composition and for
the amount and position of erythromycin in different phases. The three medicated feed were then administered
orally by means of a gastric probe to rainbow trout and their relative bioavailability was estimated
in comparison with that obtained after oral administration of feed with erythromycin powder.
For each medicated feed, 80 fish were tested. Finally, plasma profiles of erythromycin after single administration
of medicated feeds were used to predict profiles obtainable by administering once-daily medicated
feeds for 7 consecutive days. The results proved that the feeds containing microemulsified
erythromycin provided largely superior oral bioavailability and the advantage of obtaining the same efficacy
against bacterial infections with a much lower dose of drug
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Preparation of sustained release co-extrudates by hot melt extrusion and mathematical modelling of in vitro/in vivo drug release profiles
No full textAim of this work was to develop a cylindrical co-extrudate characterised by an in vivo sustained
release profile by means of a hot-melt extrusion process. Co-extrudate was made up of two concentric extruded matrices: an inner one having a hydrophilic character, based on polyethylene glycol, and an outer one with lipophilic character, based on microcrystalline wax. Both segments contained theophylline as a model drug. A screening between several devices differing for dimensions (diameter and length) and relative proportions of the inner and outer part was carried out on the basis of their in vitro drug release and the release mechanism was studied by means of a mathematical model. The co-extrudate exhibiting the desired sustained release was selected for in vivo bioavailability studies. In vivo studies confirmed the achievement of the purpose of the research, demonstrating the desired release of theophylline on four healthy volunteers. Accordingly, hot-melt extrusion process is a viable method to produce in a single step co-extrudates showing a sustained release. In addition, the developed mathematical model proved to be a reliable descriptor of the both in vitro and in vivo experimental data
An innovative oxytetracycline self-emulsifying formulation for fish diets: preparation, characterisation and oral bioavailability in rainbow trout (Oncorhyncus mykiss) and in European sea bass (Dicentrarchus labrax)
No full textThe aim of this study was to develop a self-emulsifying system (SES) with practical applications in fish farming. In particular, the lipid vehicle
was developed in order to deliver oxytetracycline hydrocloride to rainbow trout (RT) and European sea bass (ESB) so as to improve the drug’ s
oral bioavailability. The developed formulation was assessed in comparison to an aqueous solution working with two fish species (one fresh-water
and one salt-water), after oral administration with a gastric probe. Results indicated an enhancement of bioavailability of 5.86 and 5.41 times
over the aqueous solution, in RT and ESB, respectively. SES was then used to prepare medicated feed containing the formulation. The pharmacokinetic
of this feed was evaluated after oral administration and compared to that of commercial OTC medicated feed. The bioavailability of OTC
delivered in SES was 3.2 times higher in RT and 2.7 times higher in ESB, than OTC supplied by commercial medicated feed. This bioavailability
enhancement was confirmed when RT were fed by classical administration in fish tanks of single and repeated administration of OTC delivered
in SES and commercial medicated feed, attesting to better absorption of the SES formulation
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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