In vitro percutaneous absorption of all-trans retinoic acid applied in free form or encapsulated in stratum corneum lipid liposomes.

The objective of this study was to design an all-trans retinoic acid (RA) topical release system that modifies drug diffusion parameters in the vehicle and the skin in order to reduce systemic absorption and the side-effects associated with topical application of the drug to skin. Three cases of application of hydrogels containing RA either in free form or encapsulated in stratum corneum lipid liposomes (SCLLs) have been considered. For this purpose, we have evaluated the RA in formulations with combinations of Carbopol Ultrez 10 (U10) and hyaluronic acid (HA) for percutaneous absorption. In vitro permeability experiments with [3H]-t-RA were carried out using a Franz-type diffusion cell in abdominal rat skin samples. Accumulation of the drug in the surface and skin layers was evaluated by both the tape stripping method and a dissection technique, and subsequently, all the radiolabelled samples were analyzed by liquid scintillation counting. The results show that RA encapsulation not only prolongs drug release but also promotes drug retention by the viable skin. At the same time, interaction between RA and HA has an obstructive effect on diffusion, which contributes to the formation of a reservoir of the latter.

Rheological characterization of hydroalcoholic gels--15% ethanol--of Carbopol Ultrez 10.

The rheological behaviour of Carbopol Ultrez 10 ethanolic (15%) gels was studied as a function of two main variables: pH (4.0-7.0) and the polymer concentration (0.1-0.5%). Flow curves of all hydroalcoholic gels were adjusted to the Ostwald model. Sigmoidal dose response functions were obtained to describe the pH dependence of consistency index of the systems. The concentration dependence of flow indexes was best adjusted to one-phase exponential decay functions. Finally, by substituting in the power law expression, an empirical model is given to estimate viscosities of gels for any value of pH and polymer concentration in the ranges evaluated. As a result, the influence of the variables on polymer network is meaningfully assessed by means of the obtained empirical parameters: bottom value (Ymax), pH value required for a 50% polymer network development (pH50), and asymptotic flow index value for the fully structured gels (n(min)).

Viscosity and temperature relationship in ethanol/water mixtures gelified with Carbopol Ultrez 10.

The rheological characterization of Carbopol Ultrez 10 ethanolic (15%) gels is complemented by studying flow behavior as a function of temperature (20-50 degrees C) at different pH (4.0-7.0) and polymer concentrations (0.1-0.5%). Flow curves were adjusted to the Ostwald model, showing a fall in viscosity, together with an enhancement in flow index with increasing temperature. Calculated flow activation energies at constant shear rate (Egamma) were found to be related to the final pH of hydroalcoholic gels. Nevertheless, at the polymer concentration range evaluated, no significant correlations were obtained between activation energy and concentration. In general, the Carbopol Ultrez 10 gels exhibit little viscosity change under the temperature variations of normal use and storage, which minimizes possible unacceptable changes in the product's characteristics.

Development of a cream from a self-emulsifying base and moisturizing actives.

This research study is based on the design and development of a semisolid emulsion system whose novel self-emulsifying base and preferentially moisturizing actives were investigated to find out whether the system mentioned could be used as a dermatological treatment for highly sensitive skins, including atopic ones. Thus, one of the main objectives of the present study consisted of in vivo evaluation of its effectiveness by means of non-invasive assessment techniques currently employed in cosmetology. Due to the fact that the new formula is, in principle, designed for skins that could present any kind of alteration, the current study was focused on rheological parameters of viscosity, thixotropy, and extensibility to guarantee not only an accurate assessment of composition but also a comfortable and safe application on skin.

Pharmacotechnical caracterization and effectiveness study of a dermopharmaceutical form: rosemary honey contributions as a moisturizing active.

We have designed, elaborated and studied a dermopharmaceutical form formulated on the basis of a modern self-emulsifying excipient and rosemary honey (known as Miel de La Alcarria--Spain--according to the Governing Council), in order to obtain a hight degree of cutaneous hydratation. The formulation is typified and characterized from a pharmacotechnical and rheological points of view. In this sense, the experimental protocol has emphasized rheological essays which give relevant practical information. Also, we have performed a complete study of it physical and structural stability, and, lastly, we evaluated the dermopharmaceutical effectiveness. The work plan included the following tests: 1) Pharmacotechnical Essays--organoleptic characteristics, photomicrograh study, type of interposition, pH-determination, rheological and thixotropic study and physical stability tests; 2) Dermopharmaceutical Effectiveness Assays--Corneometric and Sebumetric measurements. From the results, we have deduced that the emulsified binary system that is proposed, stable from a physical and structural points of view, presents confirmed properties and a very good cosmetological adequation. In this sense, our emulsion presents a high degree of moisturizing/emollient power that qualifies it not only as a magnificent eudermic dermopharmaceutical form, but also as a very appropriate vehicle for Dermopharmaceutical and/or Dermatological Formulation.

[Dermo-pharmaceutical efficacy of emulsions with NEO-PCL: galenic and rheological studies]. / Efficacité dermopharmaceutique d'émulsions à base de NEO-PCL: études galénique et rhéologique.

The future EU prohibition (Directive 86/609/CEE) of using experimentation animals has induced the implementation of non-invasive techniques which are to substitute the present methods. Two non-invasive techniques are used to determine the cosmetological effectiveness of two emulsions formulated on a modern excipient NEO-PCL Base. Furthermore, the incorporation of multiflower honey is analyzed, being carried out the appropriate essays in order to obtain its tipification from a galenic and rheological point of view. After the formulation adjustment, O/W emulsioned systems, eudermic pH, and the rheological parameters to its application on the skin are obtained. Out of the effectiveness study, a high moisturization/emolliency degree is deduced. On the other hand, we conclude that multiflower honey rises the moisturizing power on this kind of products.

Proposal and pharmacotechnical study of a modern dermo-pharmaceutical formulation for cold cream.

Cold-Creams have been used since the times of Galen (II cA.D.) as dermo-pharmaceutical and cosmetic emulsions. This paper proposes a modern Cold-Creams formulation with variations to improve both the formula as well as the properties and applications of the traditional cerates. Basically, a modern self-emulsionable excipient with isopropyl myristate is proposed. This substance is completely analysed from the galenic and pharmaco-technical viewpoints and the analysis is completed with a study of cosmetic or dermo-pharmaceutical effectiveness and topical application on skin. The results clearly show the advantages of the new formula which are: it is easy and comfortable to prepare, very adequate for cosmetology with satisfactory stability and rheological qualities and a high degree of moisture/emollient power make it appropriate as a vehicle for the active principle in Dermopharmacy and Cosmetology.