In-Vivo Tape Stripping Study with Caffeine for Comparisons on Body Sites, Age and Washing

A Highly Efficient and User-Friendly Sensitive Skin Model on the Forearm

BACKGROUND

Sensitive skin is a worldwide skin problem, and its assessment of therapeutic efficacy traditionally relies on the facial stinging test. However, this test possesses certain limitations due to its restrictive application site, intense pain sensation, and adverse effects on physical appearance.

OBJECTIVE

This study aimed to develop and evaluate a highly efficient and user-friendly sensitive skin simulation model, which combines tape stripping and capsaicin testing on the forearm (FA-TS-CAT), as an alternative to the facial stinging test.

METHODS

A randomized, double-blind, placebo-controlled clinical trial was conducted involving 74 subjects. Skin redness (a* value), transepidermal water loss (TEWL), and self-assessment questionnaires were collected at different time points for analysis.

RESULTS

Tape stripping 5 times and 10 min application of capsaicin test were identified as the optimal conditions for the FA-TS-CAT model. Consistent stimulation and natural recovery trends of a* value and TEWL were observed on both the FA-TS-CAT and facial capsaicin test (F-CAT) models within 50 min. After the 4-t-butylcyclohexanol complex emulsion was applied, the a* value in the FA-TS-CAT model exhibited a soothing trend similar to the F-CAT model, with a significantly reduced by 3.99-fold and 3.28-fold at T3 and T4 (p < 0.001), compared to the placebo. Notably, the test efficiency of the FA-TS-CAT model was threefold higher than that of the F-CAT model, and subjects showed more willingness to participate in the FA-TS-CAT test (95.95% vs. 4.05%).

CONCLUSIONS

These results indicated the FA-TS-CAT is a highly efficient and user-friendly model for sensitive skin, providing a reliable and valid method for clinical research in sensitive skin treatment.

Revisiting the Effect of Aging on the Transport of Molecules through the Skin

Both intrinsic and extrinsic aging lead to a series of morphological changes in the skin including the flattening of the dermal-epidermal junction, increased stratum corneum dryness, reduction in sebaceous gland activity and enzyme activity as well as atrophy of blood vessels. In this study, the impact of these changes on the transport of molecules through the skin was revised. The increase in the number of transdermal formulations on the market in recent decades and life expectancy represent the main reasons for an in-depth discussion of this topic. Furthermore, elderly subjects have often been excluded from clinical trials due to polypharmacy, raising concerns in terms of efficacy and safety. In this way, ex vivo and in vivo studies comparing the transport of molecules through the mature and young skin were analyzed in detail. The reduced water content in mature skin had a significant impact on the transport rate of hydrophilic molecules. The lower enzymatic activity in aged skin, in turn, would explain changes in the activation of prodrugs. Interestingly, greater deposition of nanoparticles was also found in mature skin. In vivo models should be prioritized in future experimental studies as they allow to evaluate both absorption and metabolism simultaneously, providing more realistic information.

Cutaneous Pharmacokinetics of Topically Applied Novel Dermatological Formulations

Novel formulations are developed for dermatological applications to address a wide range of patient needs and therapeutic challenges. By pushing the limits of pharmaceutical technology, these formulations strive to provide safer, more effective, and patient-friendly solutions for dermatological concerns, ultimately improving the overall quality of dermatological care. The article explores the different types of novel dermatological formulations, including nanocarriers, transdermal patches, microsponges, and microneedles, and the techniques involved in the cutaneous pharmacokinetics of these innovative formulations. Furthermore, the significance of knowing cutaneous pharmacokinetics and the difficulties faced during pharmacokinetic assessment have been emphasized. The article examines all the methods employed for the pharmacokinetic evaluation of novel dermatological formulations. In addition to a concise overview of earlier techniques, discussions on novel methodologies, including tape stripping, in vitro permeation testing, cutaneous microdialysis, confocal Raman microscopy, and matrix-assisted laser desorption/ionization mass spectrometry have been conducted. Emerging technologies like the use of microfluidic devices for skin absorption studies and computational models for predicting drug pharmacokinetics have also been discussed. This article serves as a valuable resource for researchers, scientists, and pharmaceutical professionals determined to enhance the development and understanding of novel dermatological drug products and the complex dynamics of cutaneous pharmacokinetics.