The effect of 3 moisturisers on skin surface hydration: Electrical conductance (Skicon-200), capacitance (Corneometer CM420), and transepidermal water loss (TEWL)

Variability of Skin Pharmacokinetic Data: Insights from a Topical Bioequivalence Study Using Dermal Open Flow Microperfusion

Purpose

Dermal open flow microperfusion (dOFM) has previously demonstrated its utility to assess the bioequivalence (BE) of topical drug products in a clinical study. We aimed to characterize the sources of variability in the dermal pharmacokinetic data from that study.

Methods

Exploratory statistical analyses were performed with multivariate data from a clinical dOFM-study in 20 healthy adults evaluating the BE, or lack thereof, of Austrian test (T) and U.S. reference (R) acyclovir cream, 5% products.

Results

The overall variability of logAUC values (CV: 39% for R and 45% for T) was dominated by inter-subject variability (R: 82%, T: 91%) which correlated best with the subject’s skin conductance. Intra-subject variability was 18% (R) and 9% (T) of the overall variability; skin treatment sites or methodological factors did not significantly contribute to that variability.

Conclusions

Inter-subject variability was the major component of overall variability for acyclovir, and treatment site location did not significantly influence intra-subject variability. These results support a dOFM BE study design with T and R products assessed simultaneously on the same subject, where T and R treatment sites do not necessarily need to be next to each other. Localized variation in skin microstructure may be primarily responsible for intra-subject variability.

Noninvasive Skin Barrier Assessment: Multiparametric Approach and Pilot Study

The epidermal barrier function is disrupted in various inflammatory skin diseases. Accurate methods to measure skin barrier function are needed to assess the effect of therapeutic agents. Therefore, we developed a noninvasive multiparametric approach to measure four different parameters regarding the skin barrier. In the current pilot study, we evaluate this method in 14 healthy volunteers. We assessed erythema, transepidermal water loss (TEWL), water content, and epidermal thickness at both cheeks before and 30 min after application of Lanette and Vaseline-Lanette cream. For this, we used spectrophotometry, the Aquaflux device, the Epsilon device, and reflection confocal microscopy, respectively. Stratum corneum (SC) thickness was significantly increased after application of both creams (p < 0.05), and this increase was larger after Lanette cream compared to after Vaseline-Lanette cream (p = 0.035). Erythema, TEWL, and water content did not significantly change after cream application. Our multiparametric approach is promising and offers a feasible and practical way to quickly obtain multifaceted information about skin barrier function. Further exploration of this approach after prolonged use of cream and in conditions of disrupted skin barrier are recommended areas for future research.

Emollient treatment of atopic dermatitis: latest evidence and clinical considerations

Aim

To review current classes of emollients in the market, their clinical efficacy in atopic dermatitis (AD) and considerations for choice of an emollient.

Methods

PubMed Clinical Queries under Clinical Study Categories (with Category limited to Therapy and Scope limited to Narrow) and Systematic Reviews were used as the search engine. Keywords of ‘emollient or moisturizer’ and ‘atopic dermatitis’ were used.

Overview of findings

Using the keywords of ‘emollient’ and ‘atopic dermatitis’, there were 105 and 36 hits under Clinical Study Categories (with Category limited to Therapy and Scope limited to Narrow) and Systematic Reviews, respectively. Plant-derived products, animal products and special ingredients were discussed. Selected proprietary products were tabulated.

Conclusions

A number of proprietary emollients have undergone trials with clinical data available on PubMed-indexed journals. Most moisturizers showed some beneficial effects, but there was generally no evidence that one moisturizer is superior to another. Choosing an appropriate emollient for AD patients would improve acceptability and adherence for emollient treatment. Physician’s recommendation is the primary consideration for patients when selecting a moisturizer/emollient; therefore, doctors should provide evidence-based information about these emollients.

Clinical studies in dermatology require a post-treatment observation phase to define the impact of the intervention on the natural history of the complaint

The use of a post-treatment period of observation or "regression phase" is common in pharmaceutical and cosmetic clinical dermatology studies. Regression phases can be incorporated into a variety of study designs, ranging from simple post-treatment observation for a defined period, as has been used for moisturizers, antidandruff formulations, and treatments for acne, to more complex randomized intermittent-treatment designs, as used in studies of psoriasis pharmacotherapies. Extensive information can be derived from a regression phase. Notably, it can provide useful data on the persistence of effect and time to relapse after treatment cessation, which are particularly relevant to skin conditions in which consumer or patient adherence to treatment is suboptimal. By incorporating a regression phase, a clinical study can more closely reflect "real-world" behavior, e.g., the switching by consumers from antidandruff to beauty shampoos. The regression phase can also help to differentiate between products that show similar effectiveness during the treatment phase, and monitoring post-treatment physiological end points can provide valuable evidence on the safety and mechanism of action of the therapy.

Skin Characteristics in Patients with Pityriasis Versicolor Using Non-Invasive Method, MPA5

Background

Skin pigmentary changes of pityriasis versicolor may occur as either hyperpigmented or hypopigmented lesions, depending on the outcome of interactions between Malassezia yeasts and the skin, such as lipoperoxidation process, stimulus of inflammatory cell to melanocytes, and increased thickness of keratin layer.

Objective

To investigate skin characteristic factors that enhance the susceptibility to Malassezia yeasts and provoke different color changes of pityriasis versicolor patients.

Methods

To clarify these factors, we investigated the skin characteristics of pityriasis versicolor patients, using a non-invasive method known as MPA 5® (Courage and Khazaka, Germany). A total of 90 normal healthy subjects and 30 pityriasis versicolor patients were included in this study.

Results

Both hyperpigmented and hypopigmented pityriasis versicolor skin lesions showed higher humidity, increased sebum excretion rate and increased transepidermal water loss (TEWL) values than normal healthy subjects. But no significant difference of specific Malassezia yeasts species between hyperpigmented and hypopigmented skin lesions was evident.

Conclusion

These results indicate that higher humidity and increased sebum level provide a better growing environment of Malassezia yeasts in the skin, leading to the assumption that interaction between Malassezia yeasts and skin barrier materials makes disruption of skin barrier causing increased TEWL.