A new dry-coated device for the release of drug after a programmable period of time is proposed. It is intended to be used mainly in the therapy of those diseases which depend on circadian rhythms. ...Some core formulations, characterized by different release rates and mechanisms (containing diltiazem hydrochloride or sodium diclofenac as model drugs), were coated by compression with different polymeric barrier layers (press-coated systems). The shell formulations tested contained either gellable or erodible polymers. The dissolution profiles of uncoated cores and press-coated devices were compared. The gellable and/or erodible characteristics (properties) of the barrier formulations were also examined by means of a penetrometer. The coatings prevent drug release from the core until the polymeric shell is completely eroded or swollen. This delay in release start is not influenced by the core composition and depends only on the shell formulation. Except for the time-lag, the release kinetics of the drug contained in the core are not significantly influenced by the presence of the erodible barrier, but can be widely modulated using a swellable polymeric shell.
Encapsulation in a barium alginate membrane is a promising strategy to obtain a three dimensional culture of living cells: membrane properties are crucial for a realistic clinical application. A ...one-step encapsulation technique, recently developed for controlled release of boar semen, was employed to prepare barium alginate and protamine-alginate membranes: permeability to two model molecules (haemoglobin and glucose) was evaluated. Capsules were evaluated for technological properties and scanning electron microscopy was used to examine the external morphology of the capsules and the 3D distribution of the cells within the core. The results indicate that 3D arrangement and cell shape are maintained, capsule dimensions and mechanical properties can be modulated, as well as their permeability to model molecules such as haemoglobin and glucose.
In this study we consider some different approaches to analyze the in vitro dissolution behaviour of different dosage forms containing nifedipine. Because this drug is practically insoluble in water, ...the in vitro release characteristics of the formulations were verified using different dissolution methods. A new sustained-release dosage form, formulated in two different strengths: 30 and 60 mg, was tested and compared to an extended-release commercial product. Initially, the dissolution tests were carried out with the paddle method, in a large amount of water (5 1), to maintain the ‘sink conditions’. Then the release tests were repeated using aqueous solutions of sodium dodecyl sulphate (SDS) as dissolution fluid (in 5 1, first, and then in 1 1 of medium). Different supramicellar concentrations of the surfactant were used to verify how the different dissolution media could influence the release characteristics of the formulations proposed. The commercial product was tested in the same experimental conditions and was considered as reference dosage form. The results show that the surfactant concentrations above 0.50% are able to dissolve the drug content of all the dosage forms tested. Above this concentration, the dissolution profiles from the delivery systems considered are not affected by the presence of different percentages of SDS.
This work deals with the preparation of corticosteroid-loaded albumin microspheres designed for intra-articular administration. Dexamethasone was chosen as the model drug and bovine serum albumin was ...used as the biodegradable, natural polymer. Albumin microspheres were produced by spray drying, a 'one-step' technique seldom used in the preparation of microparticulate drug delivery systems with particle sizes < 10 microns. The effects of both polymer/drug ratio used in the formulations and the different heat-stabilization conditions were evaluated on morphology, size, solubility characteristics, drug loading and 'in vitro' drug release of the microparticles.
A previous paper dealt with the preparation of an in vitro programmable zero-order drug delivery system in which the area of the surface exposed to the dissolution medium and the macromolecular ...relaxation of polymer controlled the release of the drug. In the present study, the preparation of similar delivery systems is described, in which differing drugs and polymers were used to ascertain the mechanism governing the drug-release kinetics. The movement of the interfaces between solvent and system was measured during drug release in systems with varying composition. The results indicate that the synchronization of the movement of swelling and eroding fronts at the solvent-system interface determines the achievement of the linear-release kinetics of such swelling activated systems and that the swelling and dissolution characteristics of the polymer employed for core preparation govern front movement.
The dissolution rate of a drug poorly soluble in water, ursodeoxycholic acid, was improved by using dissolution rate enhancers belonging to the group of cellulose and starch derivatives. Different ...techniques (mixing, milling and solvent evaporation) were utilized to prepare drug/carrier systems. The determination of the improved dissolution performance of the drug from the systems has been carried out by a modified in vitro dissolution test apparatus combined with HPLC analysis of the drug. The carriers and the techniques used for improving the dissolution rate, the dissolution apparatus and the HPLC method are proposed here to solve both the dissolution rate problems of the drug and its analytical determination.
Carbamazepine is an important anti-convulsant drug, characterized by a low water solubility. In order to improve its dissolution rate, drug:polymer systems were prepared using cross-linked ...polyvinylpyrrolidone (Polyplasdone XL®-10) as dissolution rate enhancer. The systems were obtained by mixing, milling and solvent evaporation.
The systems, characterized by improved drug dissolution rate, were studied by: Scanning Electron Microscopy (SEM), X-Ray Diffraction Powder (XRD), and Differential Scanning Calorimetry (DSC).
The purpose of this study was to investigate the possibility to develop different levels of correlation between ‘in vitro’ dissolution parameters and ‘in vivo’ pharmacokinetic parameters for four ...salbutamol sulphate formulations: two commercially available formulations (Ventolin® Oral and Volmax®) and two sustained-release formulations (SG7 and SG14) developed in our laboratory. A level A correlation of ‘in vitro’ release and ‘in vivo’ absorption could be set up for individual plasma level data by means of the deconvolution method. Linear correlations could be obtained when dose fraction released ‘in vitro’ was plotted vs. dose fraction absorbed ‘in vivo’, with correlation coefficients between 0.97 and 0.99 for the formulations studied. A second level of correlation between mean ‘in vitro’ dissolution time (MDT) and mean ‘in vivo’ residence time (MRT) was performed with a correlation coefficient of 0.81. Finally, it was also possible to establish a good ‘in vitro’-‘in vivo’ correlation when the mean dissolution time ‘in vitro’ and T
max or C
max ‘in vivo’ were compared, but it appeared impossible to establish any correlation between mean dissolution time (MDT) and AUC.
Ten strains of lactobacilli were evaluated for the administration of viable microorganisms to restore the normal indigenous flora in the treatment of urogenital tract infections (UTI) in women. As ...the strains considered are facultative anaerobes, optimization of the production process was particularly critical to preserve bacterial viability. The microorganisms were formulated in single- and double-layer vaginal tablets. The two layers were characterized by different release properties: one is an effervescent composition that ensures a rapid and complete distribution of the active ingredient over the whole vaginal surface; while the second is a sustained release composition capable of releasing the lactobacilli over a longer period of time. Three different retarding polymers were tested, and all the formulations and tablets were evaluated in terms of technological processability, bacterial viability and stability, and cell adhesion properties of the microorganisms. From the results obtained, three out of ten strains appear particularly suitable for their application in the treatment of UTI. A larger batch of tablets made with a mixture of the three strains was then evaluated, confirming the feasibility of their industrial production and a good bacterial viability in the final dosage form.
