1,721,005 research outputs found
Design and characterization of bilayered buccal films as paediatric dosage form for systemic administration of propranolol
No full textBuccal mucosa has emerged as an attractive site for systemic administration of drug in paediatric patients. This route is simple and non-invasive, even if the saliva wash-out effect and the relative permeability of the mucosa can reduce drug absorption (Lam et al., 2014). Mucoadhesive polymers represent a common employed strategy to increase the contact time of the formulation at the application site and to improve drug absorption. Among the different mucoadhesive dosage forms, buccal films are particularly addressed for paediatric population since they are thin, adaptable to the mucosal surface and able to offer an exact and flexible dose (Borges et al., 2015; Trastullo et al., 2016).
The objective of the present study was to develop bilayered buccal films for the release of propranolol hydrochloride, a non-selective β1 and β2 adrenergic antagonist, indicated in paediatrics for the treatment of hypertension. Mucoadhesive layer was prepared by casting and drying of solutions of film-forming polymers, such as polyvinylpyrrolidone (PVP) or polyvinylalcohol (PVA), added with different weight ratios of gelatin (GEL) or chitosan (CH). In order to achieve unidirectional drug delivery towards buccal mucosa, an ethylcellulose coating layer was applied onto the first one. Bilayered films were characterized for their physico-chemical and functional properties.
The inclusion of CH into PVP and PVA films provided the best mucoadhesion ability, probably due to their highest hydration among all the formulations, that ensured a good interpenetration and entanglement between polymer and mucin chains. Moreover, the positively charged ammino groups of CH could interact with negatively charged sialic acid and sulphate residues of mucin glycoprotein. Films containing CH provided a lower drug release with respect to films containing GEL, due to their lower viscosity in the gelled state which limited drug diffusion. The presence of CH also increased the amount of permeated drug through buccal mucosa, thanks to its ability of interfering with the lipid organization. Coating layer did not interfere with drug permeation, but it could limit drug release in the buccal cavity.
With polymeric films, a novel solid buccal formulation was developed. The selection of suitable polymeric mixture allowed the modulation of the mucoadhesive ability, the release of the drug and its permeation through the buccal mucosa. Moreover, polymeric films fulfill all current demands for child-appropriate dosage forms. In fact, they combine the convenience of tablets, a solid dosage form, with less issues instability than liquid formulations, and the opportunity to avoid swallowing of a large unit. Moreover, the use of films with different sizes enables the administration of variable doses of drug and can be suitable for a large range of age groups.
Borges A.F., Silva C., Coelho J.F., Simões S. Oral films: current status and future perspectives. I – Galenical development and quality attributes. J. Control. Release 206 (2015) 1-19.
Lam J.K., Xu Y., Worsley A., Wong I.C. Oral transmucosal drug delivery for pediatric use. Adv. Drug Deliv. Rev. 73 (2014) 50-62.
Trastullo R., Abruzzo A., Saladini B., Gallucci M.C., Cerchiara T., Luppi B., Bigucci F. Design and evaluation of buccal films as paediatric dosage form for transmucosal delivery of ondansetron. Eur. J. Pharm. Biopharm. 105 (2016) 115-121
Ondansetron Buccal Administration for Paediatric Use: A Comparison Between Films and Wafers
Full text linkThe objective of this study was the development of different solid formulations, such as wafers and films, for buccal administrationofondansetron,aselective andpotentantagonistof5-hydroxytryptamine 3receptorsused in children for the treatment of nausea and vomiting. Wafers and films have been prepared drying an aqueous solution of pectin, hydroxypropyl methylcellulose, sodium hyaluronate, sodium carboxymethylcellulose, chitosan or gelatin, through lyophilization or oven. Formulations were characterized in terms of morphology, drug solid state and ability to hydrate, adhere to mucosa, release and favour the permeation of the drug through porcine esophageal epithelium, used as model of human buccal epithelium. The most promising formulations were tested for in vitro biocompatibility in human pulp fibroblasts. Films showed greater hydration and mucoadhesion abilitiesand allowedthe release andthepermeation ofa greateramount ofondansetron withrespect to wafers. Chitosan or hyaluronate provided films with the best mucoadhesion properties and good biocompatibility profile. Moreover, chitosan based film allowed to obtain the highest amount of permeated drug and could represent a novel child-appropriate dosage form able to combine the advantages of solid dosage form with the possibility to avoid the swallowing
Freeze-Dried Matrices for Buccal Administration of Propranolol in Children: Physico-Chemical and Functional Characterization
No full textBuccal matrices represent a widely accepted dosage form permitting a convenient, easy, reliable drug administration and reducing administration errors. The aim of this study was the development of mucoadhesive buccal matrices for propranolol administration in children. Matrices were obtained by freeze-drying of drug loaded polymeric solutions based on gum tragacanth (GT), pectin (PEC), hydroxypropylmethylcellulose (HPMC), sodium hyaluronate (HA), gelatin (GEL), chitosan (CH) or a mixture of CH and HPMC (CH/HPMC). Matrices were characterized for drug solid state, morphology, water-uptake, mucoadhesion ability, in vitro drug release and permeation through porcine epithelium. The most promising formulations were tested for in vitro biocompatibility in human dental pulp fibroblasts. The preparative method and the polymeric composition influenced the drug solid state, as a complete amorphization as well as different polymorphic forms were observed. GEL and PEC guaranteed a fast and complete drug release due to their rapid dissolution, while for the other matrices the release was influenced by drug diffusion through the viscous gelled matrix. Moreover, matrices based on CH and CH/HPMC showed the best mucoadhesive properties, favoured the drug permeation, in virtue of CH ability to interfere with the lipid organization of biological membrane, and were characterized by a good biocompatibility profile
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
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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