Polymer Tablet Matrix Systems for the Controlled Release of Dry Betula pendula Leaf Extract.

The aim of the study was to develop polymer matrix tablets with modified release of dry Betula pendula leaf extract and to investigate basic parameters influencing the drug release pattern. To fully assess the statistical significance of the influence of the individual factors in the tablet formulation development as well as the combination of them, Tukey's tests and a complete 33 factor analysis of variance (ANOVA) were applied. The following three factors were studied at three levels (low, medium and high): influence of the hydrophobic/hydrophilic polymer ratio Ethylcellulose (EC)/Hydroxypropyl methylcellulose (HPMC) (40/60, 25/75 and 10/90), influence of HPMC molecular weight (500 kDa, 750 kDa and 1150 kDa), and influence of the compression force applied (1 t, 1.5 t and 2 t). The effect of these varied parameters on the drug release parameter t80 was evaluated statistically. Twenty-seven tablet models were formulated, including all possible combinations of the variables. The obtained drug release profiles demonstrated that a 25/75 (EC/HPMC) ratio was the most suitable for prolonging the release process. Increasing the molecular weight of HMPC from 500 kDa to 750-1150 kDa and applying higher compression force significantly influenced the studied t80 values and caused sustained drug release (t80 up to 7.97 h). The combination of the hydrophilic HPMC polymer with the hydrophobic EC can result in the formation of a promising drug-carrying matrix, offering effective control of the drug release process.

Taste Masking of Enalapril Maleate by the Precipitation Method.

BACKGROUND: Taste masking of bitter or unpleasant drugs is an important prerequisite to improve patient compliance, especially for children and elderly patients. We aimed at obtaining taste-masked microparticles intended for incorporation into orodispersible tablets (ODTs). We selected the precipitation method using enalapril maleate (ENA) as a model bitter-tasting drug and Eudragit EPO® as a pH sensitive polymer. AIM: The aim of this study was to obtain microparticles with enalapril maleate by the precipitation method in order to mask the bitter taste of the drug. MATERIALS AND METHODS: Nine models of enalapril maleate ­ Eudragit EPO® microparticles were prepared by the precipitation method at varied drug-polymer ratios. The models were characterized in terms of size, shape, production yield, drug content, encapsulation efficiency and moisture content. Fourier-transformed infrared spectroscopy, powder X-ray diffraction and differential scanning calorimetry were used to analyze possible interactions in the complex. In vitro drug release in simulated salivary fluid and in vivo taste evaluation in rats were realized to prove taste masking. RESULTS: The particle size distribution varied from 266.9 µm to 410.9 µm. The shape of the resulting particles was irregular. The production yield varied from 23.6% to 78.2%. The drug content ranged between 2.3% to 4.8%, encapsulation efficiency increased from 1.6% to 9.0%. In vitro drug release data indicated significant taste masking. CONCLUSION: Some of the obtained microparticles by the precipitation method showed satisfactory taste masking efficiency, which proved the taste masking feasibility of this method.

Chemical cross-linking: A feasible approach to prolong doxylamine/pyridoxine release from spray-dried chitosan microspheres.

Spray-dried chitosan microparticles have been widely exploited as vehicles for mucosal drug delivery. Despite their advantages as pharmaceutical formulations, one of the major challenges is achieving sustained drug release, which would diminish toxicity and dosage frequency. The aim of this study was to formulate mucoadhesive glutaraldehyde cross-linked chitosan microparticles loaded with doxylamine succinate and pyridoxine hydrochloride as potential nasal drug delivery systems with sustained release. Microparticle models were formulated via spray-drying technique, using glutaraldehyde in different concentrations (0.1-1.0 mg/mL) as a cross-linking agent for chitosan. The obtained particles were with spherical shape, smooth surface and median diameter of 4 µm. The drug entrapment efficiency was high (80.47%-94.25%), indicating a tendency to decrease at higher glutaraldehyde concentrations. FTIR data demonstrated that there were no chemical interactions between glutaraldehyde and the drugs. The in vitro studies showed that the cross-linking process substantially limited particles swelling. The cross-linked particles exhibited sustained drug release characteristics at pH 6.8 over a period of 5 h with an initial burst-effect in the first 30 min. Drug release followed Korsmeyer-Peppas kinetics. Although a decrease of the particles mucoadhesive properties was observed after modification, all cross-linked formulations demonstrated high in vitro adsorption of mucin. The proposed models of mucoadhesive microsphere with sustained drug release are a perspective ground for further development of a novel delivery system for nasal administration of doxylamine and pyridoxine.

Advanced spectrophotometric chemometric methods for resolving the binary mixture of doxylamine succinate and pyridoxine hydrochloride.

The prediction power of partial least squares (PLS) and multivariate curve resolution-alternating least squares (MCR-ALS) methods have been studied for simultaneous quantitative analysis of the binary drug combination - doxylamine succinate and pyridoxine hydrochloride. Analysis of first-order UV overlapped spectra was performed using different PLS models - classical PLS1 and PLS2 as well as partial robust M-regression (PRM). These linear models were compared to MCR-ALS with equality and correlation constraints (MCR-ALS-CC). All techniques operated within the full spectral region and extracted maximum information for the drugs analysed. The developed chemometric methods were validated on external sample sets and were applied to the analyses of pharmaceutical formulations. The obtained statistical parameters were satisfactory for calibration and validation sets. All developed methods can be successfully applied for simultaneous spectrophotometric determination of doxylamine and pyridoxine both in laboratory-prepared mixtures and commercial dosage forms.

Antioxidant Activity of Dry Birch (Betula Pendula) Leaves Extract.

BACKGROUND: Betula pendula is widespread in Europe and Asia. It has been used in traditional medicine since ancient times. Birch leaf extracts are known to exhibit a number of pharmacological activities. Antioxidant activity has also been reported. AIM: The aim of this work was to investigate the antioxidant activity of a dry leaf extract from Betula pendula Roth. MATERIALS AND METHODS: The total flavonoid content was determined. Some of the most commonly used methods were applied to evaluate the antioxidant capacity of the extract in vitro and in vivo. The ability of the extract to scavenge DPPH free radicals was evaluated by the method described by Brand-Williams with suitable modifications. ABTS decolorization assay was also applied. The in vivo assay was performed after acute and chronic administration of the extract into white albino rats, in a dose of 100 and 500 mg/kg bw. The antioxidant potential of the plasma was determined using FRAP reagent. RESULTS: A total flavonoid content of 42.5 mg/g was found, expressed as quercetin. The antioxidant activity against ABTS was concentration and time dependent. For example the concentration of 200 µg/ml led to 70.95% - 99.46% scavenging activity. DPPH scavenging activity was found to be about 98% at a concentration of 80 µg/ml. The extract possesses antioxidant potential, comparable with that of Trolox, in acute application. In chronic application, poorer results are observed, probably due to biotransformation and elimination processes. CONCLUSION: Dried birch leaf extract has a relatively high antioxidant potential and could be used as a natural source of antioxidants.

Optimization of Chitosan Microspheres Spray Drying via 32 Full Factorial Design.

BACKGROUND: Generally, the preparation of spray-dried microspheres is strongly affected by the process parameters. Particle size and production yield are mainly influenced by the spraying solution concentration and the pump rate of the spray dryer. AIM: The aim of this study was to assess optimum spray drying parameters - polymer concentration and pump rate required for the production of chitosan microspheres with high production yield and targeted for nasal administration particle size. MATERIALS AND METHODS: Full 32 factorial design was used to study the investigated parameters. Three different concentrations of the chitosan solution were selected: a low concentration of 1%, average concentration of 1.5% and high concentration of 2%. The rate of the peristaltic pump was also varied at three levels: low rate of 10%, medium rate of 14% and high rate of 18%. RESULTS: Nine models of chitosan microspheres were formulated and characterized in terms of shape, surface morphology, size, particle size distribution and production yield. The particles obtained from 2% chitosan solutions, sprayed at 10% pump rate were of the highest yield (64.33%) and appropriate for nasal administration median diameter (3,434 µm). CONCLUSION: The two investigated spray-drying parameters interact with each other and their influence on the production yield and the size of the chitosan microspheres should be evaluated together, instead of one at a time. The assessed process parameters allow the production of chitosan microparticles with high yield and desirable characteristics (size, size distribution and shape) for intranasal delivery.

Ketoprofen-loaded polymer carriers in bigel formulation: an approach to enhancing drug photostability in topical application forms.

The purpose of the study was to investigate the stability and biopharmaceutical characteristics of ketoprofen, loaded in polymeric carriers, which were included into a bigel in a semisolid dosage form. The polymer carriers with in situ-included ketoprofen were obtained by emulsifier-free emulsion polymerization of the monomers in aqueous medium or a solution of the polymers used. The morphological characteristics of the carriers, the in vitro release and the photochemical stability of ketoprofen were evaluated. The model with optimal characteristics was included in a bigel formulation. The bigel was characterized in terms of pH, rheological behavior, spreadability, and in vitro drug release. Acute skin toxicity, antinociceptive activity, anti-inflammatory activity, and antihyperalgesic effects of the prepared bigel with ketoprofen-loaded polymer carrier were evaluated. The carriers of ketoprofen were characterized by a high yield and drug loading. The particle size distribution varied widely according to the polymer used, and a sustained release was provided for up to 6 hours. The polymer mixture poly(vinyl acetate) and hydroxypropyl cellulose as a drug carrier, alone or included in the bigel composition, improved the photostability of the drug compared with unprotected ketoprofen. The bigel with ketoprofen-loaded particles provided sustained release of the drug and had optimal rheological parameters. In vivo experiments on the bigel showed no skin inflammation or irritation. Four hours after its application, a well-defined analgesic, anti-inflammatory, and antihyperalgesic effect was registered. The polymer mixture of poly(vinyl acetate) and hydroxypropyl cellulose as a carrier of ketoprofen and the bigel in which it was included provided an enhanced photostability and sustained drug release.

Formulation and performance evaluation of betahistine dihydrochloride microspheres as sustained release systems.

UNLABELLED: Betahistine dihydrochloride is a histamine-like drug widely used in relieving the symptoms associated with Ménière's syndrome. Pharmacokinetic studies of betahistine have demonstrated that it has a short plasma half-life of 3-4 hours. In such cases frequent administration of the drug is required in order to keep plasma concentration within the therapeutic range. However, this may lead to noncompliance and aggravate patients' comfort. An advanced approach for achieving sustained release of drugs is their incorporation in microparticulate carriers. AIM: To design a sustained release microsphere formulation of betahistine providing reduced dose frequency and lower risk of side effects occurrence. MATERIALS AND METHODS: Betahistine-loaded chitosan microspheres were obtained via W/O emulsion solvent evaporation technique and were characterized for particle size, drug loading and entrapment efficiency. Drug release into phosphate buffer saline pH 7.4 was performed and dissolution profiles of the formulations were obtained. To study the mechanism of drug release from the microspheres the dissolution data was fitted to various mathematic models. RESULTS: Betahistine-loaded microspheres were produced with a high drug loading and entrapment efficiency. The microcarriers were spherical in shape with mean particle size of 3.82 µm to 7.69 µm. Betahistine release studies from the microspheres showed similar and slightly increasing dissolution profiles. The drug release proceeded in a controlled manner following Fickian diffusion. CONCLUSION: The obtained results suggest that betahistine-loaded chitosan microspheres prepared by solvent evaporation method are capable of sustained release of drugs and therefore can be used as drug delivery systems in the treatment of Ménière's syndrome.