For the modelling of the kinetics of diffusion and relaxation in the polymer matrix, the power law equation in a two-parameter or three-parameter form is employed. The introductory part of the paper summarizes the employed varieties of the power law equation including the equation making it possible to distinguish diffusion from relaxation. The liberation kinetics of pilocarpinium chloride from lyophilized lamellae with graded amounts of hydroxypropylmethylcellulose is expressed by power law equations and their parameters are compared. The conclusion discusses the usability of the power law equation in the modelling of liberation of active ingredients and recommends the use of the three-parameter power law equation with a shift of the liberation out of the origin of the coordinates.

• MeSH
• chemie farmaceutická MeSH
• deriváty hypromelózy MeSH
• difuze MeSH
• lyofilizace MeSH
• methylcelulosa analogy a deriváty   MeSH
• pilokarpin farmakokinetika   MeSH
• tablety MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• deriváty hypromelózy MeSH
• methylcelulosa MeSH
• pilokarpin MeSH
• tablety MeSH

One of the possibilities of how to optimize bioavailability of drugs after topical ophthalmic administration is prolongation of the period of contact of the preparation with the eye tissue. The most usual way of achieving this gaol is an increase in the viscosity of the preparation by an addition of a suitable auxiliary substance. At present besides hydrogels and mucoadhesive substances, also polymers which produce the sol-gel phase change are employed for this purpose. This so-called in situ gelation takes place in a very short period of time after contact with the eye tissue due to a change in temperature, pH, or interaction with physiological ions. The present paper aims to survey in situ gelling polymeric substances, which are examined in relation to their use in ophthalmic administration.

• MeSH
• biologická dostupnost MeSH
• farmaceutické pomocné látky * MeSH
• gely MeSH
• oční roztoky * MeSH
• polymery * MeSH
• polysacharidy MeSH
• viskozita MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• farmaceutické pomocné látky * MeSH
• gely MeSH
• oční roztoky * MeSH
• polymery * MeSH
• polysacharidy MeSH

On modelling the kinetics of dissolution, two variants of Weibull equation in a two-parameter or tree-parameter form are used, the estimations of their parameters not being quite comparable. The introductory part of the paper sums up four variants of the equation and chracterized their relationship to granulometric Rosin-Rammler-Sperling equation. The kinetics of liberation of pilocarpinium chloride from lyophilized lamellae with graded amounts of hydroxypropylmethylcellulose is expressed by the above-mentioned equations and their parameters are compared. The conclusions generally discusses the usability of equations and their correct interperetation in modelling dissolution of active ingrediens from dosage forms.

• MeSH
• chemické jevy MeSH
• chemie fyzikální MeSH
• deriváty hypromelózy MeSH
• kinetika MeSH
• methylcelulosa * analogy a deriváty   MeSH
• pilokarpin * MeSH
• rozpustnost * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• deriváty hypromelózy MeSH
• methylcelulosa * MeSH
• pilokarpin * MeSH

Microbial contamination of ophthalmic drops means a risk of serious injury to the eye. Ophthalmic drops must therefore comply with sterility requirements. Protection of multiple-dose drops against secondary contamination is ensured by an addition of an antimicrobial agent. Selection of a suitable antimicrobial agent is conditioned by many factors, such as the spectrum of effect, properties of the preparation, compatibility with the components of the preparation and the container, and the technology of manufacture. Although the added antimicrobial substance ensures the safety of the preparation, on the other hand it can produce a number of negative effects in the eye tissue. The present paper summarizes pharmacopoeial requirements for microbial quality of ophthalmic drops, outlining the properties and efficacy of antimicrobial substances commonly used in ophthalmic drops (benzalkonium chloride BAC, cetrimide CTM, phenyl mercuric salts PHg, thiomersal TM, chlorobutanol ChB, benzyl alcohol BA, phenyl ethyl alcohol PEA, chlorohexidin ChX, parabens PB), their typical concentrations and combinations, including the parameters of formulation and the interactions which affect their activity. It deals with the toxicity of these antimicrobial substances, side effects on the eye tissue, and alternatives to the use of antimicrobial agents.

• MeSH
• antiinfekční látky škodlivé účinky   analýza   normy   MeSH
• kontaminace léku prevence a kontrola   MeSH
• lidé MeSH
• oči účinky léků   MeSH
• oční roztoky chemie   normy   MeSH
• stabilita léku MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antiinfekční látky MeSH
• oční roztoky MeSH

The precision of dosing of powder drugs in piece dosage forms can be theoretically forecast by means of statistical principles of variability of random mixtures, the use of which for this purpose has been traditionally examined. The present critical review of the literature of the subject is primarily focused on random mixing of powder mixtures, their homogeneity, volume dosing, and the use of a correlogram in the examination of nonrandom and segregated mixtures. The knowledge is useful both for the selection of a suitable particle size and for the verification of suitability of the employed parameters of mixing and the technological processing of the obtained mixture.

• MeSH
• léčivé přípravky chemie   MeSH
• prášky, zásypy, pudry chemie   MeSH
• statistické modely MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• léčivé přípravky MeSH
• prášky, zásypy, pudry MeSH

Bovine serum albumin was heterogeneously dispersed in the terpolymer of DL-lactic acid, glycolic acid, and mannitol. The terpolymeric carrier was plasticized by triacetin, tributyrin, or a mixture of triacetin with tricaprylin. Matrices were prepared by mixing a melt of the carrier with the plasticizer and albumin. Liberation was tested in 1/15 mol.l-1 phosphate buffer pH 7.4 and took place in two stages--the burst and the stage of the continual process. The burst represented 30% to 90% of liberated albumin. The second, continual stage began on day 4 of liberation and within ten days maximally 10% of the total amount of albumin was released. The course of liberation was most markedly influenced by the parameters of the oligoester carrier, its molecular weight, and the degree of branching. The total extent of albumin liberation was influenced partly by its irreversible adsorption on the carrier, partly by its polymerization. The extent of adsorption and polymerization of albumin was increased with the molecular weight of the carrier and decreased with the increasing degree of its branching. Albumin liberation was positively influenced by the presence of plasticizers in matrices, triacetin being demonstrated as the best one.

• MeSH
• biodegradace MeSH
• kapryláty MeSH
• nosiče léků * MeSH
• polymery * MeSH
• sérový albumin hovězí * MeSH
• triacetin MeSH
• triglyceridy * MeSH
• zvláčňovadla * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kapryláty MeSH
• nosiče léků * MeSH
• polymery * MeSH
• sérový albumin hovězí * MeSH
• triacetin MeSH
• tributyrin MeSH Prohlížeč
• tricaprylin MeSH Prohlížeč
• triglyceridy * MeSH
• zvláčňovadla * MeSH

The fractal character of exponential particle size distribution makes it possible to use fractal dimension for the evaluation of the results of granulometric analysis. The conditions of sedimentation analysis of talc in aqueous solution were optimized by adding nonionogenic tenside and deflocculation electrolyte. Dispersion analysis demonstrated the suitability of minimally 0.2 g/l of polysorbate 80 for talc soaking. In the evaluation of pharmaceutical granulometry, it is advisable to supplement the usually reported specific surface area with fractal dimension, which primarily contributes to a more general interpretation of variability of particle size.

• MeSH
• chemie farmaceutická * MeSH
• fraktály * MeSH
• mastek MeSH
• roztoky MeSH
• velikost částic * MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• mastek MeSH
• roztoky MeSH

Lactitol ranks among sugar alcohols which are employed as dry binders in the manufacture of tablets, particularly the chewable ones. Water-granulated lactitol is the directly compacting form of this substance. The present paper studies the compressibility of the granulated form of lactitol and the effects of different concentrations of the lubricant magnesium stearate on the strength and disintegration time of the compacts from his substance. Lactitol cannot be compressed without an added lubricant. Magnesium stearate, employed in two concentrations, 0.4% and 0.8%, did not negatively interfere with the strength of the compacts. The disintegration period of tablets was prolonged with increasing stearate concentration, but independently of compression force.

• MeSH
• chemie farmaceutická MeSH
• cukerné alkoholy * MeSH
• kyseliny stearové MeSH
• pevnost v tlaku MeSH
• tablety * MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cukerné alkoholy * MeSH
• kyseliny stearové MeSH
• lactitol MeSH Prohlížeč
• stearic acid MeSH Prohlížeč
• tablety * MeSH

Vivapur is microcrystalline cellulose manufactured by the German firm J. Rettenmeier & Söhne GmbH + Co. The types Vivapur 102 and 12 enjoy priority use as dry binders for direct tablet compression. The present paper evaluates tensile strength of tablets made from these substances and the effect of an addition of the lubricant magnesium stearate in connection with its concentration and the conditions of the process of mixing, particularly the period and intensity of mixing. The tested concentrations of stearate were 0.4 and 0.8%, the tested periods of mixing being 2.5, 5, 10, and 20 minutes, intensities of mixing 17 and 34 rot./min. Sensitivity of dry binders to added stearate was evaluated by means of the LSR (lubricant sensitivity ratio) values. The results demonstrated higher sensitivity to an addition of the lubricant in Vivapur 12 than in Vivapur 102. In the first part of the paper focused on the effect of stearate concentration on tensile strength of tablets, Vivapur 102 was also compared with Avicel PH-102. Tablets from Vivapur 102 alone were stronger than those from Avicel PH-102. A concentration of stearate of 0.8% decreased the binding capacity of Vivapur 102 more than that of Avicel PH-102. With a prolonged period of mixing and increased intensity of mixing with stearate, tensile strength of tablets from both Vivapur types was decresed, and a prolonged period of mixing exerted a more marked effect on Vivapur 12 and increased intensity of mixing, on Vivapur 102.

• MeSH
• celulosa * MeSH
• chemie farmaceutická MeSH
• farmaceutické pomocné látky * MeSH
• kyseliny stearové * MeSH
• tablety * MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• celulosa * MeSH
• farmaceutické pomocné látky * MeSH
• kyseliny stearové * MeSH
• stearic acid MeSH Prohlížeč
• tablety * MeSH
• vivapur MeSH Prohlížeč

Colloidal aqueous dispersions of 2 to 5% (weight) of hydroxypropylmethylcellulose (HMPC 4000) yield pseudoplastic mucilages and gels. Rotational viscosimetry in the cone-plate arrangement enables rapid and reproducible evaluation of the transitional region between pseudoplastic and plastic deformation, characterized by Herschel-Bulkley equation. To the traditional Ostwald's two-parameter relationship it adds a third one, revealing a deviation from the beginning of the coordinates of the rheogram caused by the limiting yield stress. The obtained equations make it possible not only to estimate apparent and real viscosity, but also the area under the curve of the pseudoplastic rheogram. The actual precondition of integration, however, is the estimation of the limiting yield stress as the shear rate for the zero shear stress. Experimental estimation of the bottom margin for the integration of the area under the curve makes mutual comparability of rheograms possible. At a temperature of 32 degrees C, analysis of variance demonstrated a significant diminution of this area in the presence of about 2% of pilocarpinium chloride.

• MeSH
• chemické jevy MeSH
• chemie fyzikální MeSH
• deriváty hypromelózy MeSH
• methylcelulosa analogy a deriváty   chemie   MeSH
• PEG-DMA hydrogel chemie   MeSH
• pilokarpin * MeSH
• pružnost MeSH
• viskozita MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• deriváty hypromelózy MeSH
• methylcelulosa MeSH
• PEG-DMA hydrogel MeSH
• pilokarpin * MeSH