The modern drug alaptide, synthetic dipeptide, shows regenerative effects and effects on the epitelisation process. A commercial product consisting of 1% alaptide hydrophilic cream is authorised for use in veterinary practice. This study focuses on the formulation of alaptide into semi-synthetic polymer-based hydrogels. The aim of the present study is to prepare hydrogels and to evaluate the liberation of alaptide from hydrogels. The hydrogels were prepared on the basis of three gel-producing substances: methylcellulose, hydroxyethylcellulose and hydroxypropylcellulose. To enhance the drug release from hydrogel humectants, glycerol, propylene glycol and ethanol in various concentrations were evaluated. The permeation of the alaptide from gels into the acceptor solution was evaluated with the use of the permeable membrane neprophane. The amount of drug released from prepared hydrogels was determined spectrophotometrically. Hydrogels with optimal alaptide liberation properties were subjected to the study of rheological properties in the next phase. The optimal composition of hydrogel as established in this study was 1% alaptide + 3% hydroxyethylcellulose with the addition of 10% glycerol as humectant. Due to the advantageous properties of hydrogels in wounds, alaptide could be incorporated into a hydrogel base for use in veterinary medicine. , gel-producing substance, humectant, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose Hydrogel research increased significantly in the last decades; due to their properties, hydrogels are widely used as suitable bases of preparations in human and veterinary medicine. The properties of hydrophilic gels, or hydrogels, are significantly different from those of ointments and creams. Hydrogels are usually formed by hydrophilic polymers which under certain conditions and polymer concentrations create a gel with a high percentage of water. They can additionally contain glycerol or propylene glycol as humectants and ethanol as an antimicrobial agent. Hydrogels create a smooth film that adheres well, can be removed easily and exhibits a cooling effect. The active substances have been dispersed in hydrogels (dissolved, suspended or emulsified). The base with the incorporated active ingredient must have suitable properties, especially biocompatibility and chemical, microbiological and physical stability (Bronaugh and Maibach 2001). EpitelisationPeptide drugs are becoming an essential part of modern therapy. Beside their therapeutic effect they can perform the function of another non-peptide drug carrier. Their reactions on changes of the pH milieu, biocompatibility, thermosensitivity and good mechanical properties have been reported (Galaev and Mattiasson 2008).Alaptide is spirocyclic synthetic dipeptide, chemically prolyl-leucyl-glycine amide derivative (Nedvidková et al. 1994). Due to its positive influence on regenerative processes in various skin diseases it can be used in veterinary medicine. For a long time it has been used as a commercial 1% hydrophilic ...
Knowledge of the release kinetics together with its (mathematical) model is inevitable for prediction of properties and optimization of dosage forms. The ability to optimize the release kinetics is a key factor in the endeavour of increasing pharmaceutical availability. The optimization may be done by a suitable choice of the dosage form or by clever distribution of the drug in the auxiliary substances or even by using an automatically working drug delivery device. This paper describes a model-based analysis and preparation of hydrogels. The following composition was used in the experiment: Chitosan – the gel creating basis; polymer, chlorhexidine – the drug; dodecyltrimethylammonium bromide – the auxiliary substance and surfactant. The release kinetics were studied at three temperatures and were evaluated by using several models (zero order, pseudo-first order, first order, Higuchi, Hixon Crowell, Weibul distribution and Korsmeyer-Peppas). It was found that the best fitting model of the drug release was the Higuchi model. So as to predict character of the release process (exothermic and spontaneous), the activation energy, activation enthalpy, entropy and Gibbs free energy were evaluated.
This study deals with the formulation of natural drugs into hydrogels. For the first time, compounds from the sage essential oil were formulated into chitosan hydrogels. A sample preparation procedure for hydrophobic volatile analytes present in a hydrophilic water matrix along with an analytical method based on the gas chromatography coupled with the mass spectrometry (GC-MS) was developed and applied for the evaluation of the identity and quantity of essential oil components in the hydrogels and saline samples. The experimental results revealed that the chitosan hydrogels are suitable for the formulation of sage essential oil. The monoterpene release can be effectively controlled by both chitosan and caffeine concentration in the hydrogels. Permeation experiment, based on a hydrogel with the optimized composition [3.5% (w/w) sage essential oil, 2.0% (w/w) caffeine, 2.5% (w/w) chitosan and 0.1% (w/w) Tween-80] in donor compartment, saline solution in acceptor compartment, and semi-permeable cellophane membrane, demonstrated the useful permeation selectivity. Here, (according to lipophilicity) an enhanced permeation of the bicyclic monoterpenes with antiflogistic and antiseptic properties (eucalyptol, camphor and borneol) and, at the same time, suppressed permeation of toxic thujone (not exceeding its permitted applicable concentration) was observed. These properties highlight the pharmaceutical importance of the developed chitosan hydrogel formulating sage essential oil in the dermal applications.
The paper deals with the kinetics of liberation of chlorhexidine dihydrochloride (CHH) from chitosan-based hydrogels in the presence of the substance with antiseptic effect, namely benzethonium chloride at the temperature range 25 – 40 °C. The concentration of the CHH in the system was 0.1 % (w/w). The used benzethonium chloride was in concentration range of 0.1 – 1.0 % (w/w). It was found that the release of CHH is influenced by both factors: the concentration of benzethonium chloride and temperature. The release rate constants increase with increasing temperature and decrease with increasing concentration of benzethonium chloride in hydrogels. The activation energy of the release of the substance CHH from hydrogel is higher for hydrogels with higher content of benzethonium chloride. The activation energies of the benzethonium chloride release from the prepared hydrogels were virtually the same.
It is known that cationic surfactants have an antimicrobial effect and act as enhancers. This paper studies three cationic surfactants from the group of alkyldimethylbenzylammonium chlorides (dodecyl-, tetradecyl-, and hexadecyl). Interest is focused on the association of the surfactants with respect to temperature, partition balances and their influence on drug release, rheological properties, and the pH of hydrogels. The critical micelle concentrations (CMC) of the surfactants were estimated from dependencies of conductivity, density, spectrofluorimetry, and UV–VIS spectrophotometry on molarity in the temperature range of 25–50 °C. It was found that the temperature dependence of a CMC is U-shaped, with its minimum at 30 °C, and the CMC value decreases as the length of the chain increases. The pseudo-phase separation model was used for the calculation of various thermodynamic parameters, such as the Gibbs free energies (spontaneous process), enthalpies (exothermic process), and entropies of the micelles’ formation, CMCs, and the degree of counterion binding. All thermodynamic parameters, as functions of the temperature, were estimated. It was found that partition coefficients increase as the length of the alkyl chain and the pH = (5.0–7.0) increase. The influences of surfactants, below and above the CMC, on drug (chlorhexidine dihydrochloride) release from hydrogels, rheological properties, and pH at 30 °C were studied. Also, the amounts of the released drug increase as the alkyl chains of the surfactants prolongate. The amounts of the released drug with the surfactant below the CMC are greater than that above the CMC. All hydrogels (regardless of the length of the alkyl chain) exhibit a non-Newtonian pseudo-plastic flow. The results obtained will be used in the formulation of the drug and surfactants into dosage forms.
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