215 research outputs found
MECHANICAL AND COMPRESSION CHARACTERIZATION OF PELLETES PREPARED BY EXTRUSION-SPHERONIZATION
No full textPart 1 The first part concern the characterization of mechanical and compression properties of pellets prepared by extrusion-spheronization. Thirteen batches of pellets were prepared all in the same condition, using five materials (corn starch, α-lactose monohydrate, anhydrous dicalcium phosphate, peg 6000 and amidated pectin) plus microcrystalline cellulose as main binder, in fixed ratio, 75, 50 and 25% respect the cellulose amount. A further batch was prepared using only microcrystalline cellulose. A characterization program were carried out on the compression and mechanical properties of the starting materials, powder mixtures and pellets, the latter analysed either as single unit that during compression. Results showed as pellets compaction behaviour is strongly related to the properties of powder mixtures used for their preparation and it could be also derived from single components characteristics according with the ratio used. Diametrical compression tests and pellets images before and after such test enabled to link mixtures and pellets compaction behaviour, moreover these tests allowed to classify pellets as fragmenting and deforming. Despite the similar compaction mechanism mixtures and pellets behaved completely different in term of tablettability. A marked increase on surface area resulted crucial in order to obtain pellets tablets, as confirmed by the fragmenting batches results. All pellets classified as deforming seem suitable as core materials for the film coating application,in the preparation of multiparticulate controlled release tablets. They resist to the compaction process retaining their shape, so they represent good system in order the maintain the film integrity. All pellets classified as fragmenting pellets do not result useful as ''cushioning agents'' in multiparticulate controlled release tablets. Moreover the spheronization carried out on dense extrudate (as in this case) do not represent the best methodology for this purpose. Part 2 The second part, carried out at the school of pharmacy and chemistry, John Moore University (UK) under the supervision of Dr. M. Roberts, concerning the influence of hydro-ethanolic media on the aspirin release profiles from hypromellose matrices. Percent aspirin released increased with increasing levels of ethanol in the dissolution media, correlating with the drug's solubility, however,dose dumping of aspirin did not occur. An initial rapid release was observed in media comprising 40% ethanol. Release in these conditions was considered to be both erosion and diffusion-mediated, in contrast to the release in 0, 10, 20 and 30% ethanol media, where erosion-controlled release dominated. Image analysis of matrix swelling indicated a slower initial interaction between ethanol and hypromellose accounting for the initial rapid release. Cloud point studies suggested that ethanol retarded hydration of the polymer
Caratterizzazione del processo di compressione di materiali farmaceutici: approcci empirici e reologici.
No full textTablets, the most widely used pharmaceutical dosage form, are prepared by the compression process through which two punches exert pressure on mixtures of powders or granules, loaded within a confined space. Despite the apparent simplicity of the process, it is not free from problems that in some cases make it difficult to apply. In particular, the feasibility of this process is mainly related to the characteristics of the material to be compressed, such as flowability, adhesiveness and tabletability. While in the first two cases it is possible to effectively operate by the addition of suitable excipients or by introducing a further production step such as granulation, in the case of poor tabletability these solutions may not be effective in the presence of high levels of active ingredient. Low tabletability is essentially related to the rheological features of the material to be compressed and, more specifically, to a high elasticity of the material itself, which cause the production of fragile or damaged tablets (capping and lamination). Since the rheological behaviour of the materials is strictly time-dependent, these problems are more relevant by the increase of production speed and consequently they are more frequent during the production phase than in the small scale development. The analysis of compression behaviour has been a topic of interest over the years and it has been attempted to develop models that can mathematically describe this process and predict its outcome in the various materials. The first models have been developed since the 1960's. That proposed by Heckel (Trans Metal Soc Aime, 1961) is the more frequently applied. Although it has been formulated as a scientific theory, the starting point is based on an assumption that has never been verified and can therefore be considered as an empirical model. Another semi-empirical approach is that based on the calculation of compression / decompression work by force-displacement traces. In this case, the main limitation is due to the fact that some essential contributions to the definition of the various energies involved are ignored (friction and heat). In the early 1980s, the compression process began to be studied through a rheological approach. Rippie and Danielson (J Pharm Sci, 1981) were the first to attempt to define the viscoelasticity of pharmaceuticals by deriving rheological parameters directly from the compression process, while Radebaugh et al (Int J Pharm, 1989) addressed the problem by analyzing tablets through oscillatory tests. Since the mid-2000s, however, it has been attempted to develop a predictive method by linking the rheological properties of individual discrete units to be compressed with the compaction performance (Bashaiwoldu et al, Int J Pharm, 2004 and Adv Powder Technol 2011; Cespi et al, Eur J Pharm Biopharm, 2007).This last approach is the most promising though limited by the ability to perform rheological tests only when the materials consist of particles of a certain size and regular shape
Dextran and its potential use as tablet excipient
No full textDextrans are a class of carbohydrate polymers extensively applied in pharmaceutical applications, particularly as drug conjugate macromolecular carriers or drug delivery systems. These polysaccharides improve the stability of the therapeutics enabling also the control of their release, via either the parenteral and or oral routes. In the latter case, due to their gel forming ability they may have potential as hydrophilic matrix tablets for sustained drug release.
In this paper, we investigated the behaviour of different molecular weight (1, 40, 500 and 2300 kDa) dextrans as tabletting excipients. Powder particle size and hygroscopic studies have been reported, together with tabletability, tablet stability and tablet swelling. Moreover we use tramadol as model compound to evaluate the ability of dextrans to control drug dissolution. The results suggest that dextrans with lower molecular weights may be a promising excipient to be used as filler for immediate release tablets, due to their good tabletability and fast dissolution rate, while dextrans with higher molecular weights could be an efficient disintegrant due to their swelling ability
Evaluation of dibutyrylchitin as new excipient for sustained drug release
No full textDibutyrylchitin (DBC), a lipophilic chitin diester, has been synthesized from chitin and butyric anhydride with methanesulfonic acid as catalyst. Exhaustive esterification of free alcoholic groups of chitin was assessed by FT-IR and 1H-NMR spectroscopy. High degree of alkyl substitution allowed DBC to acquire an almost completely lipophilic character. Tablets of paracetamol and metformin employing DBC as major excipient, in comparison with starch, microcrystalline cellulose, lactose and polyvinylpyrrolidone, were prepared and rates of drug release were checked by dissolution test assays. DBC released drug at a lower rate than that of the other tested materials. A comparison study of rate release of metformin from DBC tablets and from metformin-hydroxypropyl methylcellulose prolonged release oral formulation available on the market has been also curried out. Under the same conditions and in the presence of the same amount of loaded drug, DBC released 64% of metformin whereas hypromellose-based tablets released 87%
Characterization and Stability of Emulsion Gels Based on Acrylamide/Sodium Acryloyldimethyl Taurate Copolymer
No full textSepineo P 600, a concentrated dispersion of acrylamide/sodium acryloyldimethyl taurate copolymer in isohexadecane, has self-gelling and thickening properties and the ability to emulsify oily phases, which make it easy to use in the formulation of gels and o/w emulsion gels. In this paper, gels were prepared using a Sepineo P 600 concentration between the 0.5% and 5% (w/w), and then emulsion gel was also prepared from the 3% Sepineo gel by adding a specific amount of almond oil. All the prepared systems were analyzed and characterized by oscillation rheology and acoustic spectroscopy. The particle size of the oil droplets and the microrheological extensional moduli (G′ and G′′) of the systems were determined from acoustic parameters and used together with the classical oscillatory rheological tests to assess the stability of the systems. Classical oscillatory analysis revealed that the dynamic moduli were very dependent on polymer concentration; as this parameter increased, there was progressive improvement in the sample elasticity. In fact, the mechanical spectra of the 0.5% and 1% (w/ w) Sepineo samples were characterized by strong frequency dependence and multiple crossover points, typical of dilute polymer solution with no organized structure. On the other hand, the 3-5% (w/w) concentration systems showed typical gel-like spectra, marked by the absence of crossover points between the dynamic moduli and by weak dependence on frequency. Nevertheless, the elastic properties of the gel-like structure even at elevated polymer concentrations were not strongly long-lasting, as demonstrated by the increase of the viscous contribution in the low frequency range during acoustic spectroscopy analysis. This fact could indicate that the gel structure is characterized by weak polymer-polymer interactions, an advantageous characteristic for topical administration, as the sample is thus easier to rub into the skin. Finally, both rheology and acoustic spectroscopy indicated that addition of the oily phase caused minimal changes to the elastic character of the gel. Thus, Sepineo P 600 gel and emulsion gel are very effective systems for use in topical and other types of applications
Evaluation of dissolution kinetics of hydrophilic polymers by use of acoustic spectroscopy,
No full textThis paper seeks to demonstrate the feasibility of using a novel analytical technique, acoustic spectroscopy, to characterize the dissolution kinetics of hydrophilic polymers, in particular, three different model polysaccharides: lambda carrageenan, gellan gum, and xanthan gum. The influence of particle size and of analysis temperature (25 or 45 °C) was evaluated through the evolution over time of the microrheological acoustic parameters G′ and G′′. This new method was then compared with classical rheological analysis. To better compare acoustic spectroscopy and rheological analysis, the initial dissolution rate from the slope of the first part of the G′ or viscosity versus time curves was calculated. Both analytical techniques gave the same rank order of kinetics for the powder types and fractions examined; differences in absolute values were due to the fact that the two methods measured different parameters and had different stirring efficiencies. The rheological data obtained with both methods of analysis and their modelling confirmed that acoustic spectroscopy is an effective tool for monitoring and quantifying dissolution kinetics and hence affords a powerful technique for following over time a great number of physical changes occurring in a specific system
THE USE OF SOUND SPEED MEASUREMENTS IN THE EVALUATION OF POLYMERS MUCOADHESIVENESS
No full textNon disponibil
HIGH RESOLUTION ULTRASONIC SPECTROSCOPY IN THE ANALYSIS OF POLOXAMERS BEHAVIOUR
No full textNon disponibil
Informe de Auditoría no. 15/21 : Recursos humanos - CESPI-UNLP
No full textEvaluar los procesos de liquidación de haberes y de designación de agentes del CESPI, su desarrollo en el marco de procedimientos aprobados y de controles eficaces a los fines de asegurar su corrección y apego a la normativa vigente. Tareas relacionadas con el ODS N°4.Universidad Nacional de La Plat
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