Dermatotoxicology of microneedles (MNs) in man.

Developed within the last few decades, microneedles (MNs) have only recently seen wide-scale use among the general population, especially in the area of cosmetics. With the FDA only starting to regulate microneedling devices and the many new microneedling products that enter the modern global market, it is of utmost importance to establish the safety profile and reasonable expectations of the microneedling practice and its products. In our review of current literature, the authors searched the keyword "microneedle" with the following terms: "safety", "side effect", "toxicology", "adverse effect", "adverse event", "infection", "dermatitis", "granuloma", "scarring", and "hyperpigmentation". Despite wide-scale implementation of MNs, we are likely only beginning to understand the potential of MNs as a medical and consumer product, and we should, therefore, be aware of any potential adverse events associated with the product.

Sebo-pharmacokinetics: a proposed percutaneous sebum egression method.

BACKGROUND/AIMS: The sebaceous gland is widely believed a critical factor in the pathogenesis of acne vulgaris. Although extensive studies document the ability of oral and topical treatments to improve acne, little is known about the quantification and mechanism of drug delivery via the sebaceous gland. A percutaneous egression method presents a way to study how drugs reaching the bloodstream can enter the skin. METHODS: A literature search was performed across databases (PubMed, Embase, and Google Scholar) and the University of California, San Francisco (UCSF) textbook library with relevant search terms. RESULTS: This search failed to reveal data on sebo-pharmacokinetics (PK); however, many articles center on pharmacodynamics (PD) - i.e. functional improvement instigated by oral or topical treatments. Experiments on humans and hamsters - representative sebaceous gland models - demonstrate indirect PD measures of sebaceous gland function. DISCUSSION: Here, we summarize the current available data on drug delivery via the sebaceous gland and suggest a practical method to directly document sebo-PK in man and animal.

Should we instruct patients to rub topical agents into skin? The evidence.

Background: At least 15 factors influence the ability of compounds to penetrate the skin. Massage (rubbing) may be another factor that has gone relatively unrecognized. Method: PubMed, Google Scholar, and EMBASE databases were accessed online in March 2018 in search of studies measuring absorption through skin with and without rubbing or massage. Results: While some studies noted no difference in dermal absorption with regards to rubbing, others have demonstrated the opposite. In general, massage technique does indeed sometimes enhance dermal absorption. In addition to increase skin temperature and blood flow, rubbing likely modifies stratum corneum (SC) structure to enhance diffusion rates and increase retained penetrant amount within the skin. Conclusions: Understanding the mechanism of massage and its role in percutaneous penetration may help elucidate skin barrier function, dermal absorption, skin decontamination, and dermatotoxicology. To achieve such goals, an in vitro model that models in vivo behaviors must first be established. Subsequently, experiments with different penetrants, vehicles, massage time, and other variables may be considered.

Stratum corneum substantivity: drug development implications.

There are at least 15 factors that influence the ability of chemicals to penetrate the skin. Substantivity is yet another factor and allows penetrants to remain on and in skin for many days. As many skin pathologies involve stratum corneum and require multiple dosing of topicals, understanding substantivity mechanisms may provide insight for topical dosing strategies. Substantivity is also of importance in the development of other consumer products that necessitate adherence to skin, including sunscreens, insect repellents, and cosmetics. Furthermore, while stratum corneum adherence may delay percutaneous penetration, reducing the risk of systemic toxicity, excessive substantivity may play a role in the toxic accumulation of harmful penetrants. Continued research in this area may offer insight into dermatotoxicology and dermatopharmacology.