1,720,964 research outputs found
Development and in vitro characterization of chitosan based microspheres for nasal delivery of promethazineDrug Development and Industrial Pharmacy,
No full textConventional and composed promethazine-loaded microspheres
were prepared by spray drying of chitosan solution systems and double water-inoil-
in-water (W/O/W) emulsion systems, respectively. Double emulsions were
prepared in two different feed concentrations, with chitosan dissolved in both
water phases, and ethylcellulose dissolved in oil phase. Swelling and bioadhesive
properties of the microspheres depended on the chitosan content, type
and the feed concentration of spray-dried system. Results obtained suggested
that better ethylcellulose microcapsules with promethazine in the chitosan
matrix were formed when less concentrated emulsion systems were spray-dried.
Thus, in case of such a system, with ethylcellulose/chitosan weight ratio of
1:2, prolonged promethazine release was obtaine
Preparation and evaluation of a melt pelletised paracetamol/stearic acid sustained release delivery system
No full textThe potential of a sustained release formulation for paracetamol produced by melt pelletisation was investigated. The chosen formulation was based on the combination of stearic acid as a melting binder and anhydrous lactose as a filler. After determination of the size distribution, the pellet characterisation included scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), specific surface area and true density determination. Hence, the in vitro release from every single size fraction (2000, 1250, 800, 630, <630 microm) was evaluated and the release mechanism was analysed with the help of an appropriate mathematical model. The results of drug content and superficial atomic composition were found to be constant in all pellets size fractions, attesting the ability of melt pelletisation in a high shear mixer to form a product with homogeneous composition. The mathematical model is built on the hypotheses that drug diffusion and solid drug dissolution in the release environment are the key phenomena affecting drug release kinetics. Smaller classes apart (particles are not perfectly spherical), the comparison between model best fitting and experimental data indicated the reasonability of these hypotheses. Moreover, model reliability is proved by its ability of predicting drug release from a known mixture of the above mentioned particles classes
Development and bioadhesive properties of chitosan-ethylcellulose microspheres for nasal delivery
No full textLoratadine-loaded microspheres were prepared by spray-drying of dispersions, emulsions and suspensions differing in polymeric composition and solvents used. Conventional microspheres were obtained by spray-drying of dispersions composed of chitosan (CM) as only polymer, while composed microspheres were obtained by spray-drying of two-phase systems composed of chitosan and ethylcellulose (EC). Microspheres differed in EC/CM weight ratio (0:1, 1:2 and 1:3) and in loratadine/polymers weight ratio (1:6 and 1:8). The entrapment efficiencies were between 67.9 and 86.1%; less loratadine was entrapped as polymer/drug ratio decreased. In comparison to one-phase systems composed of CM as only polymer, spray-drying of two-phase systems composed of both, CM and EC resulted in improved loratadine entrapment (80.1-86.1%). All microspheres were positively charged, indicating the presence of chitosan at the surface, regardless of the drug content and the type of spray-dried system. The highest zeta-potential was measured for loratadine-free conventional microspheres, consisting of chitosan only (32.7+/-1.3 mV). Tensile studies showed that both, EC/CM ratio and the type of spray-dried system influenced the bioadhesive properties of the microspheres in a way that the microspheres with higher chitosan content were more bioadhesive and microspheres prepared from suspensions were more bioadhesive than those prepared from emulsions, regardless of the same polymeric composition. The results suggested that the spray-drying method is useful to produce bioadhesive loratadine-loaded microspheres
Preparation end in vitro/in vivo characterisation of melt pelletised paracetamol/stearic acid sustained release delivery system
No full textThe potential of a sustained release formulation for paracetamol produced by melt pelletisation was investigated. After the production of the pellets, based on the combination of stearic acid as a melting binder and anhydrous lactose as a filler, the 3000-2000 μm size fraction was selected in the light of the promising in vitro dissolution results for further characterisations, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), specific surface area and true density determination. Hence the release mechanism was analysed with the help of an appropriate mathematical model. The mathematical model was built on the hypotheses that drug diffusion and solid drug dissolution in the release environment are the key phenomena affecting drug release kinetics. Bioavailability of the developed formulation was evaluated in an in vivo study in eight subjects
Investigation on the possibility of producing self-emulsifying pellets by wet granulation in high shear mixer
No full textPreparation in high-shear mixer of sustained-release pellets by melt pelletisation
No full textThe preparation of sustained-release pellets by melt pelletisation was investigated in a 10-l high shear mixer and
ternary mixtures containing stearic acid as a melting binder, anhydrous lactose as a filler and theophylline as a model
drug. A translated Doehlert matrix was applied for the optimisation of process variables and quality control of pellets
characteristics. After determination of size distribution, the pellets were characterised with scanning electron
microscopy, X-ray photoelectron spectroscopy and porosimetric analysis. Finally, the in vitro release from every
single size fraction was evaluated and the release mechanism was analysed. Since the drug release rate decreased when
enhancing the pellet size fraction, the 2000-mm fraction, exhibiting a substantially zero-order release, was selected for
further in vivo biovailability studies. These data demonstrated that pellets based on the combination of stearic acid
and lactose can be used to formulate sustained release pellets for theophylline. © 2000 Elsevier Science B.V. All rights
reserved
Preparation and in vitro/in vivo characterisation of a melt pelletised paracetamol/stearic acid sustained delivery system
No full textSelf-emulsifying pellets prepared by wet granulation in high-shear mixer: influence of formulation variables and preliminary study on the in vitro absorption
No full textA method of producing self-emulsifying pellets by wet granulation of powder mixture composed of microcrystalline cellulose, lactose and nimesulide as model drug with a mixture containing mono- and di-glycerides, polisorbate 80 and water, in a 10-l high shear mixer has been investigated. The effects of the formulation variables on pellets characteristics were evaluated by mixtures experimental design and by a polynomial model, in order to describe the phenomenon, to verify eventual interactions among components of the mixture and to investigate the feasibility of scaling-up. After determination of size distribution, the pellets were characterised by scanning electron microscopy, dissolution and disintegration tests, and by in vitro absorption test Such an approach, applied to the development of a self-emulsifying system for nimesulide as poorly water-soluble model drug, resulted in different formulations with improved drug solubility and permeability characteristics. The data demonstrate that pellets composed of oil to surfactant ratio of 1:4 (w/w) presented improvement in performance in permeation experiments
Theoretical and experimental study on theophylline release from stearic acid cylindrical delivery systems
No full textThe purpose of this study is to evaluate the possibility of developing a cylindrical sustained-release dosage form for theophylline directly by means of a ram extrusion process. In particular, the formulations contained: stearic acid as a low melting binder, monohydrate lactose and polyethylene glycol 6000 as hydrophilic fillers. The influence of type and percentage of the components was studied considering different parameters such as the time required for 50% of the drug release (t50%)and the drug diffusion coefficient in the delivery system. The choice of the different formulations to be tested is carried out employing an axial design with constraint domains. The limits of each component were fixed on the basis of preliminary trials. The analysis of the t50% values revealed that the release kinetics is mainly affected by stearic acid and theophylline content, whilst lactose effect is almost negligible. A substantial correspondence between the experimental results and the analysis of the drug release kinetics performed by means of an ad hoc developed mathematical model was found. The proposed mathematical model allows to conclude that wherever the release mechanism is initially ruled by dissolution, then diffusion plays the most important role
- …
