Biomedical subjects

R Zelkó

Publications and source records attributed to R Zelkó.

26 records · Page 2Linked to original sources

PubMed1998

Comparative evaluation of surfactant and hydrophobizing agent concentration in relation to the optimal particle size of metered-dose inhalers.

The aim of the present study was to formulate stabilized suspension-type metered-dose inhalation aerosols, and to examine the connection between the stabilizing additives and the optimal particle size. For the stabilization of the suspended particles, hydrophilic- and hydrophobic-type additives were applied. Oleil oleate was selected as a hydrophilic anionic surfactant, and the hydrophobizing agent was dimethyl siloxane polymer. The effect of the amount of the applied hydrophilic and hydrophobic additives on the optimal particle size was modeled by a second-order polynomial equation fitted to the data gathered by a face-centered central composite statistical design. We found that if the proper type and amount of additives are selected, it is possible to acquire the therapeutically best composition.

Dose-Response Relationship, Drug↗

PubMed1998

Effect of the formulation parameters on the characteristics of pellets.

Pelletization is increasingly applied currently for the preparation of solid oral controlled-release dosage forms. The production of the particles, which are regular in shape and size, can be achieved with the application of the proper polymer auxiliary materials and new pharmaceutical technological methods (extrusion, spheronization). Regularity in shape and size, attained by the optimization of several production parameters, can promote the coating procedure. Under optimal conditions, particles were prepared for coating in a high-shear mixer, which is used to produce uniform particles. The effect of the rotating speed of the applied chopper and the amount of microcrystalline cellulose in the composition on the physical characteristics of the pellets was modeled by a second-order polynomial equation fitted to the data gathered by a face-centered central composite statistical design.

Administration, Oral↗

PubMed1998

[Evaluation of substrate-binder interfacial interactions].

Substrate-binder interfacial interactions were evaluated on the basis of the physico-chemical and mechanical properties of granules and compressed samples. Linear relationship was found between the breaking strength, the diffuse reflectance and the binder content of the examined granule-systems and compressed samples. The increasing amount of binder in the granules improved the adhesive interaction existing between the substrate and the binder. Our results indicate that the mechanical properties of the single particles as well as of the compressed samples were basically determined by the physico-chemical interactions of the substrate-binder interfacial layer. The qualitative and quantitative evaluation of these interactions has a decisive impact on the formulation and in process control of solid dosage forms of optimal mechanical properties.

Binding Sites↗

PubMed1998

[Effect of physicochemical properties of polyethylene glycol derivatives on drug release from wax matrices].

The purpose of the present study was to investigate the effect of the various types and amounts of polyethylene glycols on the potassium chloride release from wax matrices. Potassium chloride as a highly water-soluble model drug was embedded into wax containing surfactants to produce sustained release dosage form. Various kinds of polyethylene glycols were chosen to control the dissolution profile. The dissolution profile of the matrix samples was characterized by the Weibull distribution. The physico-chemical characteristics--surface tension, HLB value, refractive index--of the aqueous solutions of the polyethylene glycols were also determined. On the basis of the examined physicochemical characteristics of various polyethylene glycols it is possible to select the optimal concentration of surfactant to formulate matrix dosage forms of required dissolution profile.

Chemistry, Pharmaceutical↗

PubMed1998

[Influence of auxiliary materials on the proportion of effective particle size of metered-dose suspension type aerosols].

The aim of the present study was to formulate suspension type inhalation aerosols by various types of auxiliary materials, and to select the formulation with the highest proportion of the effective particle size. The examined suspension type aerosol contained sodium cromoglycate as an active compound. For the stabilization of the suspension, the applied surface active ingredients were oleic acid and oleyl oleate, and dimethyl siloxane polymer was selected as hydrophobizing agent. Factorial design was used for the optimization of the experimental results. On the basis of our results, the correct types and amounts of auxiliary materials can be selected to obtain the therapeutically effective formulation.

Administration, Inhalation↗

PubMed1998

Effect of the substrate-binder interactions on the mechanical properties of compacts.

The effect of the substrate-binder interfacial interaction in granules, made of PVP and glass ballotini as model substrates, on the mechanical properties of rectangular compacts consisting of these granules was investigated by use of the four-point beam bending technique. The mechanical properties of the prepared compacts were correlated with the physico-chemical characteristics--contact angle, surface tension and binder concentration--of the granulation liquid. The mechanical strength and Young's modulus of the specimens both reached a maximum value when the binder concentration in the granulation liquid was increased to 20% (w/v) for all granulation liquid volumes used. Above a 20% PVP concentration, the increasing granulation liquid contact angle hindered the binder spreading, creating weak regions in the compact and decreasing its mechanical strength.

Chemistry, Pharmaceutical↗

PubMed1997

The effect of surfactant and suspending agent concentration on the effective particle size of metered-dose inhalers.

The aim of this study was to examine the influence of the concentrations of surfactant and suspending agent on the quantity of effective particles (size < 10 microm) delivered by metered-dose inhalers. A 2-factor, 3-level, face-centred central composite design was used to construct a second-order polynomial model which describes the effect of formulation factors (suspending agent, surface-active ingredient) on the therapeutically important characteristic (effective particle size) delivered by metered-dose inhalers. Oleic acid was selected as the surface-active ingredient, and the suspending agent was anhydrous alcohol. A non-linear model demonstrated with good correlation the effect of the amounts of surfactant and suspending agent on the quantity of particles of effective size. The results obtained enable determination of the correct amount of surface-active ingredient and the optimum quantity of the suspending agent, thus enabling formulation of a therapeutically effective formulation.

Chemistry, Pharmaceutical↗

PubMed1994

[Solution kinetics of magnesium oxide containing granules produced by laboratory scale fluidization].

In practice of manufacturing industrial pharmaceutical products, the technique of fluidization has been used extensively in the past decades. The authors studied the magnesium oxide-containing granulates made by fluidization granulation in laboratory, to optimize the process, to determine the neutralization kinetic parameters of granulates, to establish the connections between the method of granulation and the release of active substances. According to our findings, the pharmaceutical product's characteristics in the aspects of physics, chemistry, stability and bioavailability may remarkably change without fixing the border conditions of parameters within limits.

Kinetics↗