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Biomedical subjects

I Erös

Publications and source records attributed to I Erös.

At least 19 recordsLinked to original sources
PubMed2001

Preformulation experiences and in vitro model studies with spironolactone-containing suppositories.

The optimal suppository base for the formulation of rectal suppositories containing diuretic spironolactone was selected experimentally. Model studies were carried out about the effect of solubility-increasing additives on the release of the drug from the suppositories. During the in vitro examinations acceptor phases of different pH values were used, and both diffusion time and the number of samplings were changed. Among the lipophilic and hydrophilic suppository bases studied the hydrophilic Macrogolum 1540 was found to be optimal. The release and diffusion of spironolactone was the most favourable from these suppositories. During storage these suppositories remained stable and the values of release did not decrease significantly (p < 0.05).

Algorithms↗
PubMed2000

[Factors influencing liberation of drug from semisolid dosage forms].

Liberation of salicylic acid--as a model active agent--was investigated from white petrolatum, creams w/o and o/w types and hydrogels. Active agent was applied in suspended, dissolved forms, in inclusion complexes and solubilized state. The process of liberation was studied by a continuous through-flow method, with Hanson vertical diffusion cell. The results of experiments were evaluated by factorial design method. Increase of the concentration of salicylic acid, polarity of vehicle and solubilized state of drug increased the drug release. It was established that the partitioning released drug was the most important step of drug release. Factors changing partitioning influenced the liberation to the highest degree.

Delayed-Action Preparations↗
PubMed1998

[Optimization of bioavailability of pharmacons].

The authors have investigated the optimization possibilities of bioavailability of drugs as spray-drying, spray-embedding, spray-freezing, inclusion complex formation with cyclodextrin derivatives, mineral complex formation with bentonite and in vitro diffusion of products. The bioavailability of drugs may be significantly influenced with these methods.

Biological Availability↗
PubMed1998

[Spherical crystallization in pharmaceutical technology].

Physical properties of crystals, such as size, crystal size distribution and morphology, may predetermine the usefulness of crystalline materials in many pharmaceutical application. The above properties can be regulated with the crystallization process. The spherical crystals are suitable for direct tablet-making because of their better flowability and compressibility properties. These crystals can be used in the filling of the capsule. In this work, the spherical crystals such as "single crystal", "poly-crystals" and agglomerates with other excipients are collected from the literature and the experimental results of the authors. A close cooperation between chemists and the pharmaceutical technologists can help for doing steps in this field.

Chemistry, Physical↗
PubMed1998

[Experiences with the rectal use of a chemotherapeutic agent. 1. In vitro biopharmaceutical examinations; selection of the optimal vehicle].

The factors influencing in vitro liberation (Part 1) and in vivo absorption (Part 2) from trimethoprim-containing rectal suppositories and the authors' results related to them are reported in this two-part publication. Special emphasis was laid on selecting the optimal suppository base which is harmless physiologically yet not indifferent pharmacologically. From among the 24 compositions studied, a lipophilic mixture containing a surface active additive (Witepsol W 35) and a hydrophilic (Macrogolum) mixture were found to be the best in all respects. Liberation from the trimethoprim-containing rectal suppositories was measured with in vitro dynamic diffusion and spectrophotometrically. A power relation was found to exist between the quantity of the released pharmacon and the diffusion time, and a significant negative exponential relation was observed between the doses and their respective in vitro availability values.

Administration, Rectal↗
PubMed1998

[Experiences with the rectal use of chemotherapeutic agents. 2. Pharmacokinetic examinations with animals].

The aim of the investigations was to optimise vehicle for trimethoprim (TMP) suppositories ready for clinical trials. The rectal absorption of TMP was studied in anaesthetized rats. The drug liberation properties of the five mixed vehicles with promising in vitro results (Part 1.) were studied. The course of the blood level curves was monitored with serial sampling. The TMP concentration of blood was determined by bioassay. Individual bases were compared with the use of the pharmacokinetic parameters derived from the analysis of the obtained blood level curves, with special respect to biological availability (BA). The extent of bioavailability is influenced considerably by the hydro-, lipo- or lipohydrophilic property of the vehicle. TMP, if incorporated in the proper vehicle, is absorbed well. With three vehicles the extent of absorption exceeded the absorption seen with oral administration on the same model (BA = 38.8%). The best results were achieved with the lipophilic base Witepsol W 35 containing 10% of Polysorbate 20 and 10% of Polysorbate 61 (BA = 63.8%) and with Witepsol W 35 containing 10% of Polysorbate 60 (BA = 64.9%). The hydrophilic Macrogol 1540 vehicle containing 5% of Macrogol 400 had only slightly worse results (BA = 52.9%). In the case of the lipohydrophilic Witepsol W 35 vehicle with 10% of Polysorbate 20 and 10% of Polysorbate 61 content a significant negative exponential relation was found between the administered doses and their respective bioavailability values, this tendency had been observed during the in vitro examinations, too. No such relation was found in the case of the lipophilic Witepsol W 35 vehicle containing 10% of Miglyol 812.

Administration, Oral↗
PubMed1996

Rheological studies of creams. II. Effect of water content on rheological characteristics.

25 creams with different water content was prepared by means of five self-emulsifying waxes. The variables were the ratio of the structure forming components of the lipophilic phase, the hydrophilic emulsifier and the water content. It was concluded from the flow curves, that the investigated creams were thixotropic systems independently of the water content. The yield value, the initial, the equilibrium and the plastic viscosity decreased exponentially with the concentration of the emulsified water. The slope of the linearized exponential curve is an important structural parameter. The measure of the this parameter provides information about the position of water in the gel structure.

Emulsions↗
PubMed1996

Rheological studies of creams. III. Effect of lipophilic phase on consistency.

The 3rd part of the serial analyses the correlation between the rheological characteristics of creams and the composition of the lipophilic phase. It is proved qualitatively by comparison of flow curves of systems with identical water content, and quantitatively by changes of initial, equilibrium and plastic viscosity, that the main factor in structure formation is the interboundary interaction of the hydrophilic and the lipophilic phase. This interaction can be characterised by determining wetting. A correlation between the contact angle of wetting between the hydrophilic and lipophilic phases (the quantitative model of the interboundary interaction) and the rheological parameters was identified. A logarithmic relationship was established between the contact angle of wetting and the yield value and structural viscosity.

Emulsions↗
PubMed1995

[Thermostability of the structure of creams and gels. I. Investigation of hydrophilic creams containing Hostaphat emulsions].

The effect of temperature on the change of structure of creams containing Hostaphat emulsifiers has been investigated. The micelles consisting of hydrophilic and liphophilic surfactants are disintegrated and desolvatated on the effect of heat, therefore the evaporation of water can be resulted. This theory was verified by the correlation between rheological data and the results of derivatographic measurements. It has been established that the hydrophilic emulsifier plays an important role in thermostability.

Drug Stability↗
PubMed1994

Rheological studies of creams. I. Rheological functions and structure of creams.

Large number of washable (o/w type) creams were prepared for rheological investigation. The rheological functions known from the literature were determined in our studies. Rheological constants were determined by measurements and calculations. From these, we selected those ones which were applicable to characterize the energy status of the coherent structure and which gave the most information for practical work, elaboration of composition and evaluation of stability. These functions and parameters are the following: flow curves, viscosity vs shear time and viscosity vs temperature functions, Bingham-type yield value, plastic viscosity, structure breakdown rate constant, activation energy.

Ointments↗
PubMed1994

[Influence of viscosity on drug release from ointments, creams, gels and emulsions].

The authors studied the drug release from high number of water-free ointments, creams, emulsions and hydrogels. They targeted to find correlation between the viscosity of these pharmaceutical forms and their drug release. Neutral oil was the lipophilic phase of emulsions, the emulsifiers were from Tween and Tagat series. The creams tested consisted of ESMA ointment, Teginacid and/or Softisan emulsifiers and water in 60-80 w/w%. The drug release from Eudispert, methyl-cellulose and hydroxy-ethylcellulose gels was studied. The applied active ingredients were as follows: griseofulvin, sulfadimidine, salicylic acid and ephedrine hydrochloride. Relevant literature suggest a reciprocal correlation between the viscosity of ointments and the quantity of the released drugs. The authors confirmed the general validity of this correlation in case of the following preconditions: if the solubility and distribution of drug do not change along with the change of viscosity there is reciprocal ratio between viscosity and the quantity of drug released. This reciprocal correlation prevails only in a small range of viscosity, that is in systems resembling Newton's liquids. In cases of ointments and gels of higher viscosity a reciprocal relationship exists between the logarithm of viscosity and the quantity of drugs released.

Dosage Forms↗
PubMed1990

Investigation of drug-containing multiple phase emulsions.

We studied the efficiency of the formation of w/o/w emulsions as a function of composition and mixing time. We found that the concentration of emulsifier 1, the concentration and HLB of emulsifier 2, the viscosity of the oil phase and the external water phase as well as the mixing time in second step of preparing the emulsion characteristically influence the "efficiency" of emulsification and the stability of the emulsions.

Chemistry, Pharmaceutical↗