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Biomedical subjects

Z Vitková

Publications and source records attributed to Z Vitková.

At least 19 recordsLinked to original sources
PubMed2005

[The present and future of controlled transport of the drug into the organism].

The problems of the systems of controlled (and thus also targeted) transport of the drug into the organism is one of the burning questions of contemporary biogalenics. Various more or less successful solutions were elaborated and applied, beginning with the retardette via the so-called intelligent hydrogels to various automatically controlled implants. Modem microfluidic intelligent biomicrosystems, composed of mutually interconnected microtanks, microjets, micropumps, or microcylinders, are very promising. A natural component of the complex biomicrosystem is a sensory subsystem for the collection of information from the bio-environment and a processor for the control of the process of drug supply to the organism. The present technologies of such Bio-Micro-Electro-Mechanical Systems (BioMEMSs) make it possible to revolutionize drug transport not only by facilitating precise dosing and long-term control of the immediate amount of the supplied drug on the basis of the current condition of the patient, but also to target the drug to the site of its pharmacological effect. Though at present there are still many unsolved problems, transition from laboratory conditions to clinical practice has started, and it is only a matter of five to ten years that intelligent BioMEMSs will gradually become a routinely used dosage microform. The paper briefly surveys the present state and the next development of intelligent systems of drug supply into the body of the patient, termed Intelligent Drug Delivery Systems, Intelligent DDSs, or briefly IDDSs.

Biosensing Techniques↗
PubMed2005

[Preformulation studies of potential drug XIX M: partition coefficient].

The factors which markedly influence availability of the drug from the dosage form include also auxiliary substances, which are an inevitable component in the formulation of the drug. In the selection of auxiliary substances for a newly formulated drug, it is necessary to know that the drug is never a simple mixture of mutually independent ingredients, but a dynamic system in which various physical and chemical processes take place. The present paper aims to study the effect of auxiliary substances from the group of humectants with graded concentrations and the effect of the preservative on the partition coefficient of potential drug XIX M. Partition coefficient (P') was estimated in the system n-octanol/aqueous solution with graded concentrations of polyols. In these estimations, n-octanol simulated the horny layer, and the aqueous solution the base of the topical preparation. The auxiliary substances employed were polyols - glycerol, propylene glycol, and sorbitol in 5, 10, 15, and 20% concentrations and an antimicrobially effective solution of Ajatin (Solution benzododecinii bromati) in two concentrations of 0.01 and 0.1 wt %. It follows from the obtained results that the values of partition coefficient of potential drug XIX M are greatly influenced by auxiliary substances. The value of this parameter, and therefore also biological availability, depend not only on the sort of the polyol used and its concentration, but also on the concentration of the preservative employed, in this case Ajatin.

Anesthetics, Local↗
PubMed2005

[Effect of polymer concentration on rheological properties of Carbopol 980 hydrogels containing trimecainium chloride].

Rheological properties exert influence on the manufacturing processes, stability and usability of a dosage form as well as the biological availability of an active ingredient. The present paper examines the effect of Carbopol 980 concentration on rheological properties of hydrogels with and without trimecainium chloride for a period of 2, 7, and 14 days after their preparation. On the basis of an evaluation of the changes in structural viscosity in dependence on the period of measurement, it has been concluded that for formulation of trimecainium chloride to a dermal dosage form, Carbopol 980 concentrations of 0.5 and 1.2 % are suitable.

Acrylic Resins↗
PubMed2005

[Pre-formulation studies of the H1-antihistamine loratadine for a topical dosage form].

The paper focuses on the formulation of the antihistamine loratadine for hydrogels. In the first stage of this study, the evaluated polymer for the preparation of hydrogels was Carbopol 980 of concentrations of 0.5, 0.8, and 1.0%. The paper aimed to determine the optimal concentration of Carbopol 980 in hydrogel formulation on the basis of the evaluation of the rheological properties and biological availability of loratadine from prepared hydrogels. The results of the study show 0.5% hydrogel of Carbopol 980 to be optimal for loratadine from the standpoint of topical administration.

Acrylic Resins↗
PubMed2005

[Effect of humectants on pharmaceutical availability and rheological properties of loratadine-containing hydrogels].

The paper examines the formulation of the antihistamine loratadine into hydrogels, the polymers under evaluation being Carbopol 980 and Vivastar P 5000. As other pharmaceutical auxiliary substances from the group of humectants are an indispensable component of hydrogels, the paper evaluates their influence (glycerol--GL, propylene glycol--PG, and sorbitol--SO) on the structural viscosity and pH of hydrogels as well as pharmaceutical availability of loratadine. On the basis of the results of the study it can be concluded that from the viewpoint of dermal administration of loratadine the hydrogels of the following composition are optimal: 0.5% Carbopol 980 + 5% SO and 1.5% Vivastar P 5000 + 5% PG.

Chemistry, Pharmaceutical↗
PubMed2005

[Effect of humectants on pharmaceutical availability and rheological properties of cetirizine-containing hydrogels].

The paper is concerned with the formulation of the antihistamine cetirizine into hydrogels. The cellulose derivatives hydroxyethylcellulose (HEC) and methylcellulose (MC) were employed to prepare hydrogels. As auxiliary substances from the group of humectants are indispensable components of hydrogels, the paper examines their effect (glycerol--GL, propylene glycol--PG, and sorbitol--SO) on the rheological properties and pharmaceutical availability of cetirizine in its formulation into hyrogel. The obtained results show that from the viewpoint of dermal administration for cetirizine at this stage of research hydrogels of the following composition are optimal: 3% HEC + 15% GL and 2.5% MC + 10% SO.

Cellulose↗
PubMed2004

[Effect of pharmaceutical aids on physico-chemical indicators in solutions of substance XXII B].

Within a study of optimization of auxiliary substances in the formulation of a hydrogel containing a potential local anaesthetic agent, substance XXII B, the paper evaluated the effect of a preservative (Ajatin) and humectants (glycerol, propylene glycol, sorbitol) on selected physicochemical indices, which included the partition coefficient, surface tension, and viscosity of the solutions of potential drug XXII B. On the basis of the statistical evaluation of the results, the optimal combination of auxiliary substances in this case seems to be Ajatin + glycerol.

Anesthetics, Local↗
PubMed2004

[A study of the stability of dioxopromethazine in aqueous solutions and ophthalmic instillation].

Dioxopromethazine began to be used in therapy as a modern antihistamine agent in the 1970s. A dioxopromethazine-containing ophthalmic instillation and a gel were employed until the end of the 1990s. The paper deals with the examination of the stability of the drug dioxopromethazine in aqueous solutions and the ophthalmic instillation Promefrin stored under different conditions. High-performance liquid chromatography with spectrophotometrical and electrochemical detection and HPLC connected on-line with mass spectrometry were employed for analysis. Dioxopromethazine in aqueous solutions and in ophthalmic instillations stored in direct sunlight was found not to be stable. However, the cover of the ophthalmic instillation, a brown-glass prescription bottle, and observation of storing conditions sufficiently protect the active ingredient from decomposition processes.

Chemistry, Pharmaceutical↗
PubMed2004

[Examination of the stability of hydrogen peroxide solutions].

Reliable stabilization of the pharmaceutical preparation and the active ingredient remains one of the most important problems of world pharmacy because pharmaceutical preparations are not systems which are stable without limitation. The patient must receive a quality drug and that is why the question of stability is paid grest attention to not only in research and development, industrial manufacture, but also in distribution. The measure of stability is the expiration period. Diluted solution of hydrogen peroxide (3% solution) still belongs to the most widely used and at the same time the most easily accessible disinfectants. In practice it is common both in Slovakia and abroad. It is used in several concentrations. One of its most important disadvantages is its limited stability, which markedly decreases its expiration period. The present paper investigates the stability of hydrogen peroxide solutions of routinely used concentrations (3%, 6%, and 10%) without and with a stabilizing additive (phenacetin) prepared in the pharmacy and stored under different conditions for the period of their expected usability. The content of hydrogen peroxide was assayed by the pharmacopoeial method in 7-day time intervals. All concentrations of 3%, 6%, and 10% hydrogen peroxide were found to fulfil the conditions for stability in the period of time under study. Their concentration did not fall below the limit od 90% of the content of the active ingredient, and storage under decreased temperature proved to be more suitable. Storage of hydrogen peroxide in the light is inadmissible. When the conditions of storage are observed, the required therapeutic effect of hydrogen peroxide solution can be expected for the period of three months.

Drug Stability↗
PubMed2003

[Rheologic properties of Vivastar P 5000 hydrogel].

Within the framework of pre-formulation studies, the paper evaluates the rheological properties of hydrogels whose gel-forming substance is a polymer supplied by the firm J. Rettenmaier & SöhneGMBH + CO. It is VIVASTAR P 5000, a modified derivate of carboxymethyl starch. The evaluation of rheological properties included hydrogels with 1.5, 2.0 and 2.5 w % of VIVASTAR P 5000. The highest viscosity was shown by the hydrogel with 2.0% concentration of the polymer. The system without and with the model drug with a local anaesthetic effect was thixotropic. From the viewpoint of topical administration, VIVASTAR P 5000 in 2.0% is optimal for hydrogel formulation.

Hydrogels↗
PubMed2002

[Liberation of potential local anesthetics from colloidal dispersions].

Evaluation of pharmaceutical availability of drugs from topical preparations is usually aimed to evaluate the capability of the dosage form to release the drug for its therapeutic action. Permeation cells have been used for this purpose, employing solid membranes including cellophane. Within a study of phenylcarbamic acid derivatives with local anaesthetic effect, the present paper evaluates the dosage form for topical administration containing potential drug XIX M, the chemical name N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl]-morpholinium chloride and potential drug XXII B, the chemical name N-[2-(2-octyloxyphenylcarbamoyloxy)-ethyl]-dimethylammonium chloride. The selected auxiliary substance in the formulation of the dosage form was a cellulose derivative--methylcellulose in increasing concentrations from 0.5 to 1.5%. On the basis of the obtained results it can be stated that the examined polymer methylcellulose with increasing concentration decelerated the release of both potential drugs approximately in the same way and that it can be used in practice to prolong the local anaesthetic effect.

Anesthetics, Local↗
PubMed1996

Influence of auxiliary substances on the release of heptacaine from the drug form.

In the course of the drug form development of heptacaine potential local anaesthetic, the influence of auxiliary substances on the heptacaine release and its local anaesthetic effect was studied. The obtained results show that the following auxiliary substances are optimal: a) 0.3-1.2% solution hydroxypropylmethyl cellulose for 0.025% eye drops, which have the fastest onset of the local anaesthetic effect in the hamster's eye, b) hydroxyethyl cellulose containing 0.5% heptacaine and 10% glycerol or propylene glycol for hydrogels, c) cocoa oil without and with Dimodan S for suppositories.

Anesthesia, Local↗
PubMed1996

Study of local anaesthetics. Part 139. Preformulation study of N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl] dimethylammonium chloride.

In the course of the drug form development of substance XIX B (N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl] dimethylammonium chloride [1]) the influence of auxiliary substance, namely glycerol (GL), propylene glycol (PG) and sorbitol (SO), used in the form of 5, 10, 15 and 20% solution, on the surface tension, partition coefficient, viscosity and liberation from aqueous solutions was studied. These parameters can influence the bioavailability. The obtained results show that as an optimal additive 5% SO may be used since this ensured maximal amount of liberated substance XIX B.

Anesthetics, Local↗
PubMed1995

Study of the influence of the auxiliary substances on the surface tension of the aqueous solutions of some substituted phenylcarbamic acid derivatives.

In the course of the drug form development of potential drugs the influence of auxiliary substances, namely glycerol (GL), propylene glycol (PG) and sorbitol (SO), used in the form of 5, 10, 15 and 20% solution on the surface tension (gamma) of some phenylcarbamic acid aqueous solutions was studied. Since this influence depends not only on the kind and concentration of the auxiliary substance used but also on potential drugs themselves, attempt was made to find optimal additives for particular drugs. The obtained results show that as optimal additives may be used: SO for IR-1 and H + B, for XIX M it is either PG or GL, for XIII it is GL, and finally for XIX it is either PG or SO.

Anesthetics, Local↗
PubMed1994

Study of local anaesthetics: Part 124. Influence of the ointment bases on the liberation of pentacaine chloride and heptacaine chloride.

The aim of the study was to choose a suitable base for the topical application of pentacaine chloride and heptacaine chloride. Both local anaesthetics were processed into two hydrophilic creams, two hydrophobic creams and one hydrophobic ointment as well as into three hydrogel bases. The assumption that the rate of the release of both local anaesthetics from hydrogel bases is greater than from cream bases has been fully confirmed.

Administration, Topical↗
PubMed1994

Study of the influence of auxiliary substances on the partition coefficients of some substituted phenylcarbamic acid derivatives.

In the course of the drug form development of newly synthetized potential drugs the influence of the auxiliary substances, glycerol (GL), propylene glycol (PG), and sorbitol (SO) in concentration of 5, 10, 15 and 20%, on the partition coefficient (P') of some phenylcarbamic acid derivatives was studied. Because of the great variations of this influence, attempts were made to find optimal additive for the further processing. The obtained values of P' show that an optimal additive for the drug H+B seems to be SO while in the case of the substances XIX M and XIX the optimal additives are PG or GL and SO, respectively.

Carbamates↗
PubMed1993

An evaluation of absorption using an adaptive model.

An evaluation of absorption after extravascular application of drugs, together with the evaluation of the global process of drug distribution could be considered as basic problems of pharmacokinetics. From the systems point of view, the mentioned problems have dual character and could be solved using the same approach. This paper is considered as presentation of an original approach to the evaluation of the absorption profiles. Being based on the theory of adaptive models it has some advantages in comparison with other approaches, mainly due to simple and robust algorithms without need of any special prerequisites.

Absorption↗