Uptake of two zwitterionic surfactants into human skin in vivo

Safety Assessment of Alkyl Betaines as Used in Cosmetics

The Cosmetic Ingredient Review Expert Panel (Panel) reviewed the safety of 11 alkyl betaines as used in cosmetics. These ingredients are reported to function as hair and skin conditioning agents, antistatic agents, surfactants-cleansing agents, and viscosity-increasing agents in cosmetic products. Although there are data gaps, the shared chemical core structure, similar functions and concentrations of use in cosmetics, and the expected similarities in physicochemical properties enabled grouping these ingredients and reading across the available toxicological data to support the safety assessment of each individual compound in the entire group. The Panel concluded alkyl betaines were safe as cosmetic ingredients in the present practices of use and concentration, when formulated to be nonirritating.

Development of a novel transdermal patch of alendronate, a nitrogen-containing bisphosphonate, for the treatment of osteoporosis

Bisphosphonates are widely used for the treatment and prevention of bone diseases, including Paget disease, hypercalcemia of malignancy, and postmenopausal osteoporosis. In this study, we developed a novel transdermal patch of alendronate, a nitrogen-containing bisphosphonate, for the treatment of bone diseases. The maximum permeation fluxes of alendronate through rat and human skin after application of this patch were 1.9 and 0.3 µg/cm(2) per hour, respectively. The bioavailability (BA) of alendronate in rats was approximately 8.3% after the application of alendronate patch and approximately 1.7% after oral administration. These results indicated that the transdermal permeation of alendronate using this patch system was sufficient for the treatment of bone diseases. The plasma calcium level was effectively reduced after application of the alendronate patch in 1α-hydroxyvitamin D(3) -induced hypercalcemia model rats. The alendronate patch also effectively suppressed the decrease in bone mass in model rats with osteoporosis. Modest alendronate-induced erythema of rat skin was observed after application of the alendronate patch. Incorporation of butylhydroxytoluene in the alendronate patch almost completely suppressed this alendronate-induced skin damage while maintaining the transdermal permeation and pharmacologic effects of alendronate. These findings indicate that our novel transdermal delivery system for alendronate is a promising approach to improve compliance and quality of life of patients in the treatment of bone diseases.

In vivo methods for the assessment of topical drug bioavailability

This paper reviews some current methods for the in vivo assessment of local cutaneous bioavailability in humans after topical drug application. After an introduction discussing the importance of local drug bioavailability assessment and the limitations of model-based predictions, the focus turns to the relevance of experimental studies. The available techniques are then reviewed in detail, with particular emphasis on the tape stripping and microdialysis methodologies. Other less developed techniques, including the skin biopsy, suction blister, follicle removal and confocal Raman spectroscopy techniques are also described.

An in-vitro study of the effect of hydrocolloid patch occlusion on the penetration of triamcinolone acetonide through skin in man

The aim of this study was to evaluate the effect of occlusion using hydrocolloid-containing patches on in-vitro triamcinolone acetonide (TACA) penetration of the epidermis while monitoring the uptake of water by the patches as a result of transepidermal water loss. The hydrocolloid patches were a laminate of a pressure-sensitive hydrophobic adhesive (containing a dispersion of 39% of either pectin or carmellose sodium) and a polyethylene film. The diffusion of a representative corticosteroid (TACA) through isolated epidermal sheet was shown to depend on the site from which the skin was removed. The two patch-types exhibited markedly different hydration rates when applied to the membranes. For example, after 96 h the carmellose sodium patch showed ten times the weight increase of the pectin patch. Epidermal diffusion rates were, however, similar, both showing a 3-4-fold enhancement over unoccluded conditions. The increase in TACA diffusion with the patches can be explained by the increase in skin hydration that occurs during occlusion. Despite the large differences in transepidermal water transfer through the epidermal membranes with the two types of hydrocolloid patch, however, this level of stratum corneum hydration was apparently similar. As the rate of diffusion was also independent of hydrocolloid patch component, it seems possible that the hydrophobic component of the patch matrix may also influence the level of skin hydration and consequent drug diffusion.