Assessment and clinical implications of absorption of sunscreens across skin

Repurposing FDA-Approved Drugs for Eumycetoma Treatment: Homology Modeling and Computational Screening of CYP51 Inhibitors

Eumycetoma, a chronic fungal infection caused by Madurella mycetomatis, is a neglected tropical disease characterized by tumor-like growths that can lead to permanent disability and deformities if untreated. Predominantly affecting regions in Africa, South America, and Asia, it imposes significant physical, social, and economic burdens. Current treatments, including antifungal drugs like itraconazole, often show variable efficacy, with severe cases necessitating surgical intervention or amputation. Drug discovery for eumycetoma faces challenges due to limited understanding of the disease's molecular mechanisms and the lack of 3D structures for key targets such as Madurella mycetomatis CYP51, a well-known target for azoles' antifungal agents. To address these challenges, this study employed computational approaches, including homology modeling, virtual screening, free energy calculations, and molecular dynamics simulations, to repurpose FDA-approved drugs as potential treatments for eumycetoma targeting Madurella mycetomatis CYP51. To this end, a library of 2619 FDA-approved drugs was screened, identifying three promising candidates: montelukast, vilanterol, and lidoflazine. These compounds demonstrated favorable binding affinities, strong interactions with critical residues of the homology model of Madurella mycetomatis CYP51, and stability in molecular dynamics simulations, offering potential for further investigation as effective therapeutic options for eumycetoma.

Sunscreen use associated with elevated prevalence of anti-nuclear antibodies in U.S. adults

BACKGROUND

Antinuclear antibody (ANA) prevalence in the U.S. population increased from 1988 to 2012, especially in white and more educated individuals. In adults ages 20-39 years from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and 2011-2012, ANA prevalence was previously associated with urinary concentrations of a common sunscreen ingredient, benzophenone 3, measured in winter. Spot urines may not capture relevant chronic exposures, thus we examined whether ANA was related to sunscreen use.

METHODS

In a cross-sectional study of adults ages 20-59 (N = 416 ANA positive, 2656 ANA negative, by Hep-2 immunofluorescence, 1:80 dilution), we examined associations of ANA with reported sunscreen use when in the sun for 1 h or more. Logistic regression was used to calculate covariate-adjusted prevalence odds ratios (POR) and 95 % Confidence Intervals (CI), overall and stratified by demographic factors, season, and vitamin D. We explored associations and joint effects with other sun protective behaviors and sunburn in the past 12 months.

RESULTS

The association of ANA with sunscreen differed by age (interaction p = 0.004): for ages 20-39, we saw an exposure response (POR 2.61, 95 % CI 1.50, 4.24 for using sunscreen always or most of the time, and POR 1.85; 1.12, 3.05 for less frequent versus never-use; trend p < 0.001). These associations were more apparent in females (interaction p = 0.082), non-Hispanic white and black participants (vs. other race/ethnicity, interaction p = 0.023), and those with sufficient serum vitamin D (≥50 vs. <50 nmol/L, interaction p = 0.001). ANA was not associated with other protective behaviors and not confounded or modified by these behaviors or recent sunburn.

CONCLUSIONS

These cross-sectional findings showed frequent sunscreen was associated with ANA in younger adults, supporting the need for replication, and longitudinal studies with detailed exposure histories.

Improvement of transdermal absorption rate by nonthermal biocompatible atmospheric pressure plasma

Nonthermal biocompatible plasma (NBP) is a promising option for improving medication absorption into the human skin. Currently, most plasma devices for cosmetics employ a floating-electrode plasma source for treating the skin. Human skin serves as the ground electrode in the floating-electrode plasma discharge, and discharge occurs between the skin and electrodes of the device. In this in vitro study, we aimed to evaluate the effect of NBP on the skin permeation of niacinamide. We have quantified the transdermal absorption rates of niacinamide in both untreated skin and skin treated with NBP for a duration of 10 s. The absorption of niacinamide for both without and with NBP treatment was observed until 12 h incubation time. Without plasma treatment, the human skin exhibited stable and low transdermal absorption of niacinamide up to 12 h. However, the NBP treatment significantly increased the transdermal absorption of niacinamide from 0.5 h to 6 h and continuously increased skin penetration over a duration of more than 12 h incubation period. The obtained results suggest that NBP-treated human skin showed a 60-fold higher penetration rate than non-treated skin. The increased penetration rate of niacinamide can be mainly attributed to plasmaporation subsequent to NBP treatment. The findings of this study demonstrate that NBP treatment results in remarkable skin permeability, making it a promising candidate for both cosmetic and pharmaceutical delivery applications.

Preliminary clinical pharmacokinetic evaluation of bemotrizinol - A new sunscreen active ingredient being considered for inclusion under FDA's over-the-counter (OTC) sunscreen monograph

Protection against sunburn, skin damage and the carcinogenic effects of ultraviolet light are the primary health benefits associated with UV filters used in topical sunscreen drug products. Countries such as Europe have 30+ UV filters approved for sunscreen products while the US has about 10, greatly reducing the options to provide diverse, effective sun protection products. Bemotrizinol (BEMT) is the first new sunscreen active ingredient to be evaluated for inclusion in the Over-The-Counter (OTC) sunscreen monograph using FDA's new Generally Recognized as Safe and Effective (GRASE) testing guidelines. An in vitro skin permeation test (IVPT) and clinical pilot pharmacokinetic Maximum Usage Trial (MUsT) were completed to support the GRASE determination for 6% BEMT. IVPT results indicated an oil +10% ethanol as the model sunscreen intervention for the pilot MUsT. The open-label trial revealed: BEMT concentrations rarely exceeded FDA's defined threshold (0.5 ng/mL) in plasma; no evidence for BEMT accumulation or steady-state concentrations above threshold; only one moderate and few mild treatment emergent adverse events (TEAEs). Therefore, maximal topical applications of 6% BEMT in a model sunscreen formulation did not contribute to meaningful systemic exposure. These results support the safety of BEMT 6% for human sunscreen use.

Advanced harmonization techniques result in accurate establishment of in vitro-in vivo correlations for oxybenzone from four complex dermal formulations with reapplication

Due to high variability during clinical pharmacokinetic (PK) evaluation, the prediction of in vivo exposure from in vitro absorption testing of topical semisolid and liquid dermal products has historically proven difficult. Since absorption from unoccluded formulations can be influenced by environmental factors such as temperature and humidity, maximal effort must be placed on the harmonization of experimental parameters between in vitro and in vivo testing conditions to establish accurate in vitro/in vivo correlations (IVIVC). Using four different sunscreen formulations as a model, we performed in vitro permeation testing (IVPT) studies with excised human skin and maintained strict harmonization techniques to control application time, occlusion, temperature, and humidity during in vivo human serum PK evaluation. The goal was to investigate if increased control over experimental parameters would result in decreased inter-subject variability of common topical formulations leading to acceptable IVIVC establishment. Using a deconvolution-based approach, excellent point-to-point (Level A correlation) IVIVC for the entire 12-h study duration was achieved for all four sunscreen formulations with < 10% prediction error of both area under the curve (AUC) and peak concentration (C_max) estimation. The low variability of in vivo absorption data presents a proof-of-concept protocol design for testing of complex semisolid and liquid topical formulations applied over a large surface area with reapplication in a reliable manner. This work also presents the opportunity for expanded development of testing for the impact of altered temperature and humidity conditions on product absorption in vivo with a high degree of precision.

Naringin nano-ethosomal novel sunscreen creams: Development and performance evaluation

Long term exposure of skin to UV rays produces detrimental effects such as premature skin-ageing and skin cancer. Although, zinc oxide (ZnO) and titanium dioxide (TiO₂) are good sunscreen agents, they do not provide highly efficient UV radiation protection and antioxidant and anti-aging effects. The present study was aimed at developing and characterizing ethosomes loaded with naringin and then to incorporate them into sunscreen creams containing nano-ZnO and -TiO₂ to achieve adequate skin penetration and skin retention so as to scavenge the free radicals by virtue of naringin's antioxidant property. Ethosomes were prepared and optimized with respect to concentrations of ethanol and cholesterol, time of sonication, drug and lipid ratio and amount of drug. The ethosomes were evaluated for size, zeta potential (ZP), polydispersity index (PDI), encapsulation efficiency and surface morphology. Ethosomal sunscreen creams were evaluated for physicochemical tests, spreadability, antioxidant, cytotoxicity and skin permeation studies. Optimized ethosomal formulation exhibited average vesicle size, PDI, ZP and drug encapsulation efficiency of 142.5 ± 5.6 nm, 0.199 ± 0.007, -72.5 ± 2.9 mV and 33.79 ± 1.35%, respectively. Naringin ethosomes showed enhanced retention in the skin (403.44 ± 15.33 μg/cm²) compared to naringin suspension (202.81 ± 9.45 μg/cm²). The optimized sunscreen cream exhibited SPF of 21.21 ± 0.62 with negligible permeation of naringin across the skin. Ethosomes showed pronounced skin permeation for naringin and optimized cream containing naringin ethosomes along with nano- ZnO and TiO2 showed good skin retention for naringin.

Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial

IMPORTANCE

The US Food and Drug Administration (FDA) has provided guidance that sunscreen active ingredients with systemic absorption greater than 0.5 ng/mL or with safety concerns should undergo nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies.

OBJECTIVE

To determine whether the active ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) of 4 commercially available sunscreens are absorbed into systemic circulation.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial conducted at a phase 1 clinical pharmacology unit in the United States and enrolling 24 healthy volunteers. Enrollment started in July 2018 and ended in August 2018.

INTERVENTIONS

Participants were randomized to 1 of 4 sunscreens: spray 1 (n = 6 participants), spray 2 (n = 6), a lotion (n = 6), and a cream (n = 6). Two milligrams of sunscreen per 1 cm2 was applied to 75% of body surface area 4 times per day for 4 days, and 30 blood samples were collected over 7 days from each participant.

MAIN OUTCOMES AND MEASURES

The primary outcome was the maximum plasma concentration of avobenzone. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, and ecamsule.

RESULTS

Among 24 participants randomized (mean age, 35.5 [SD, 1.5] years; 12 (50%] women; 14 [58%] black or African American; 14 [58%]), 23 (96%) completed the trial. For avobenzone, geometric mean maximum plasma concentrations were 4.0 ng/mL (coefficient of variation, 6.9%) for spray 1; 3.4 ng/mL (coefficient of variation, 77.3%) for spray 2; 4.3 ng/mL (coefficient of variation, 46.1%) for lotion; and 1.8 ng/mL (coefficient of variation, 32.1%). For oxybenzone, the corresponding values were 209.6 ng/mL (66.8%) for spray 1, 194.9 ng/mL (52.4%) for spray 2, and 169.3 ng/mL (44.5%) for lotion; for octocrylene, 2.9 ng/mL (102%) for spray 1, 7.8 ng/mL (113.3%) for spray 2, 5.7 ng/mL (66.3%) for lotion, and 5.7 ng/mL (47.1%) for cream; and for ecamsule, 1.5 ng/mL (166.1%) for cream. Systemic concentrations greater than 0.5 ng/mL were reached for all 4 products after 4 applications on day 1. The most common adverse event was rash, which developed in 1 participant with each sunscreen.

CONCLUSIONS AND RELEVANCE

In this preliminary study involving healthy volunteers, application of 4 commercially available sunscreens under maximal use conditions resulted in plasma concentrations that exceeded the threshold established by the FDA for potentially waiving some nonclinical toxicology studies for sunscreens. The systemic absorption of sunscreen ingredients supports the need for further studies to determine the clinical significance of these findings. These results do not indicate that individuals should refrain from the use of sunscreen.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03582215.

Assessment of the cytotoxicity and genotoxicity of homosalate in MCF-7

BACKGROUND

UV filters should be determined a strict toxicological safety prior to approval. Homosalate (HMS) is one of the most widely used organic UV filter. HMS accumulates in aquatic biota ecosystems and humans through the food chain; therefore, it is important to consider the effects on health and know its mechanisms of action.

AIMS

The study aimed to evaluate the cytotoxic and genotoxic effects of HMS in MCF-7 cell line.

METHODS

Cell viability was examined by the 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide (MTT) and cell membrane integrity by the lactate dehydrogenase release assays (LDH), and genotoxicity by using the micronucleus test at 250, 500, 750, 1000, 1500, and 2000 µM concentrations with the human breast cell line MCF-7.

RESULTS

Homosalate affected the cell viability dose-dependently at a concentrations of above 1000 µM. Micronucleus formation was significantly induced at 750 and 1000 µM within 24 hours due to an increase in cytostatic effect, the cell viability of HMS decreased to 57% at a concentration of 2000 µM, and a sufficient number of binucleated cells could not be obtained to count. Homosalate was also clastogenic when the cells were incubated at cytotoxic concentrations.

CONCLUSION

These results suggest that homosalate can be considered as a cytotoxic and genotoxic substance.

Safety Threshold Considerations for Sunscreen Systemic Exposure: A Simulation Study

Sunscreens are regulated as over-the-counter drugs in the United States. Some sunscreen ingredients are absorbed into the systemic circulation, which raises concerns about the safety of these drugs. There is limited information on the systemic exposure for most sunscreen ingredients. This report estimates the systemic absorption of two sunscreen active ingredients, oxybenzone and enzacamene, by developing a pharmacokinetic model from published sunscreen absorption data and compares the results with safety thresholds proposed by the US Food and Drug Administration and in the literature. Our analysis indicates that systemic absorption can be substantial, and evaluation of the systemic exposure of sunscreen ingredients is warranted to better assess any long-term risks of use.

UVA and UVB formulation phototoxicity in a three-dimensional human skin model: Photodegradation effect

In vitro three-dimensional human skin models are an innovative alternative to evaluate cytotoxicity and phototoxicity in the cosmetic industry. The aim of this study was to use a skin model to evaluate the potential toxicity of sunscreen formulations with or without exposure to UV radiation. In addition, the toxicity of these formulations was evaluated after exposure to photodegradation. The results showed toxicity with all formulations/conditions tested, including the control formulation, compared to PBS. Cell viability of photodegraded formulations - prior to the phototoxicity radiation process - was higher, indicating that some formulation components were degraded into products with reduced toxicity. The results also indicated that avobenzone was more unstable/toxic than octyl p-methoxycinnamate under the same test conditions. The sunscreens and their formulations were shown to be toxic to skin model cells to some extent, even when not exposed to UV irradiation; however the biological role of this toxicity is unclear. This result shows the importance of testing sunscreen formulations in real in-use conditions. Finally, since we used an in vitro assay based on a human cell model, this non-invasive technique represents a suitable alternative to animal models for phototoxicity tests in general and could have application in screening new sunscreen products.

Melanoma Chemoprevention: Current Status and Future Prospects

The incidence of skin cancers, both nonmelanoma and melanoma, is increasing in the United States. The ultraviolet radiation, mainly from sun, is considered the major cause for these neoplasms. While nonmelanoma skin cancers are far more numerous, melanoma remains the most challenging. This is because melanoma can become extremely aggressive and its incidence is increasing worldwide due to lack of effective early detection, as well as disease recurrence, following both surgery and chemotherapy. Therefore, in addition to better treatment options, newer means are required to prevent melanomas from developing. Chemoprevention is a reasonable cost-effective approach to prevent carcinogenesis by inhibiting the processes of tumor initiation, promotion and progression. Melanoma is a progressive disease, which makes it very suitable for chemopreventive interventions, by targeting the processes and molecular pathways involved in the progression of melanoma. This review discusses the roles of various chemopreventive agents such as NSAIDs, statins, vitamins and dietary agents in melanoma and highlights current advancements and our perspective on future of melanoma chemoprevention. Although considerable preclinical data suggest that melanoma may be prevented or delayed by a numerous chemopreventive agents, we realize there are insufficient clinical studies evaluating their efficacy and long-term safety for human use.

Bisphenol A, benzophenone-type ultraviolet filters, and phthalates in relation to uterine leiomyoma

Bisphenol A, benzophenone-type UV filters, and phthalates are chemicals in high production and use including in a range of personal care products. Exposure of humans to these chemicals has been shown to affect endocrine function. Although short-lived, widespread exposure may lead to continual opportunity for these chemicals to elicit health effects in humans. The association of these chemicals with incident uterine leiomyoma, an estrogen sensitive disease, is not known. Urinary concentrations of bisphenol A (BPA), five benzophenone-type UV filters (2-hydroxy-4-methoxybenzophenone (2OH-4MeO-BP), 2,4-dihydroxybenzophenone (2,4OH-BP), 2,2׳-dihydroxybenzophenone (2,2׳OH-4MeO-BP), 2,2׳4,4׳-tetrahydroxybenzophenone (2,2׳4,4׳OH-BP), and 4-hydroxybenzophenone (4OH-BP), and 14 phthalate monoesters were quantified in 495 women who later underwent laparoscopy/laparotomy at 14 clinical sites for the diagnosis of fibroids. Significantly higher geometric mean creatinine-corrected concentrations of BPA, 2,4OH-BP, and 2OH-4MeO-BP were observed in women with than without fibroids [BPA: 2.09µg/g vs. 1.46µg/g p=0.004; 2,4OH-BP:11.10µg/g vs. 6.71µg/g p=0.01; 2OH-4MeO-BP: 11.31µg/g vs. 6.10µg/g p=0.01]. Mono-methyl phthalate levels were significantly lower in women with than without fibroids (1.78µg/g vs. 2.40µg/g). However, none of the exposures were associated with a significant odds ratio even when adjusting for relevant covariates. There was a lack of an association between select nonpersistent chemicals and the odds of a fibroid diagnosis.

Chemometrics assisted dispersive liquid-liquid microextraction for quantification of seven UV filters in urine samples by HPLC-DAD

In the present study, dispersive liquid-liquid microextraction followed by high performance liquid chromatography-diode array detection has been developed as simple, rapid, accurate, and efficient sample preparation method for simultaneous determination of seven organic UV filters in urine samples. The influence of the main effects as well as their interactions was studied through a 2((6-2)) fractional factorial design. The candidate parameters were: type and volume of dispersant and extraction solvents, sample pH, and salt concentration. Under final optimal conditions, the analytes were extracted from 5 mL of samples by addition of 0.5 mL of acetonitrile (dispersing solvent) containing 70 μL of carbon tetrachloride (extraction solvent), without modifying the pH of the solution and applying the (+1) level of salt concentration (10% w/v NaCl). The assay was linear (R(2) > 0.997), relative recoveries ranged from 86.9 up to 97.3% and the LOQs between 3 and 45 ng mL(-1) were obtained. The intra- and interday RSDs were lower than 5 and 8% at the middle point of the linear range, respectively. The proposed method was successfully applied to different volunteer urine samples and it was shown that the extraction efficiency was not affected by the type of urine samples.

Risk assessment of excess drug and sunscreen absorption via skin with ablative fractional laser resurfacing : optimization of the applied dose for postoperative care

The ablative fractional laser is a new modality used for surgical resurfacing. It is expected that laser treatment can generally deliver drugs into and across the skin, which is toxicologically relevant. The aim of this study was to establish skin absorption characteristics of antibiotics, sunscreens, and macromolecules via laser-treated skin and during postoperative periods. Nude mice were employed as the animal model. The skin received a single irradiation of a fractional CO2 laser, using fluences of 4-10 mJ with spot densities of 100-400 spots/cm(2). In vitro skin permeation using Franz cells was performed. Levels of skin water loss and erythema were evaluated, and histological examinations with staining by hematoxylin and eosin, cyclooxygenase-2, and claudin-1 were carried out. Significant signs of erythema, edema, and scaling of the skin treated with the fractional laser were evident. Inflammatory infiltration and a reduction in tight junctions were also observed. Laser treatment at 6 mJ increased tetracycline and tretinoin fluxes by 70- and 9-fold, respectively. A higher fluence resulted in a greater tetracycline flux, but lower skin deposition. On the other hand, tretinoin skin deposition increased following an increase in the laser fluence. The fractional laser exhibited a negligible effect on modulating oxybenzone absorption. Dextrans with molecular weights of 4 and 10 kDa showed increased fluxes from 0.05 to 11.05 and 38.54 μg/cm(2)/h, respectively. The optimized drug dose for skin treated with the fractional laser was 1/70-1/60 of the regular dose. The skin histology and drug absorption had recovered to a normal status within 2-3 days. Our findings provide the first report on risk assessment of excessive skin absorption after fractional laser resurfacing.

Associations between environmental factors and incidence of cutaneous melanoma. Review

BACKGROUND

Cutaneous melanoma is one of the most serious skin cancers. It is caused by neural crest-derived melanocytes - pigmented cells normally present in the epidermis and, sometimes, in the dermis.

METHODS

We performed a review of current knowledge on the risk factors of cutaneous melanoma. Relevant studies were identified using the PubMed, Science Direct, Medline, Scopus, Scholar Google and ISI Web of Knowledge databases.

RESULTS

Melanoma incurs a considerable public health burden owing to the worldwide dramatic rise in incidence since the mid-1960s. Ultraviolet radiation exposure is the predominant environmental risk factor. The role of geographical (latitude) and individual factors such as skin type, life style, vitamin D levels and antioxidant protection, sunburn, and exposure to other environmental factors possibly contributing to melanoma risk (such as cosmetics including sunscreen, photosensitising drugs, and exogenous hormones) are reviewed in this article. Recently, both rare high risk susceptibility genes and common polymorphic genes contributing to melanoma risk have been identified.

CONCLUSIONS

Cutaneous melanoma is a complex cancer with heterogeneous aetiology that continues to increase in incidence. Introduction of new biomarkers may help to elucidate the mechanism of pathogenesis and individual susceptibility to the disease, and make both prevention and treatment more effective.

Evaluation of salicylic acid fatty ester prodrugs for UV protection

The purpose of this study was to investigate the physicochemical properties and in vitro evaluation of fatty ester prodrugs of salicylic acid for ultraviolet (UV) protection. The physicochemical properties such as lipophilicity, chemical stability and enzymatic hydrolysis were investigated with the following fatty ester prodrugs of salicylic acid: octanoyl (C8SA), nonanoyl (C9SA), decanoyl (C10SA), lauroyl (C12SA), myristoyl (C14SA) and palmitoyl oxysalicylate (C16SA). Furthermore, their skin permeation and accumulation were evaluated using a combination of common permeation enhancing techniques such as the use of a lipophilic receptor solution, removal of stratum corneum and delipidization of skin. Their k' values were proportional to the degree of carbon-carbon saturation in the side chain. All these fatty esters were highly stable in 2-propanol, acetonitrile and glycerin, but unstable in methanol and ethanol. They were relatively unstable in liver and skin homogenates. In particular, C16SA was mostly hydrolyzed to its parent compound in hairless mouse liver and skin homogenates, suggesting that it might be converted to salicylic acid after its topical administration. In the skin permeation and accumulation study, C16SA showed the poorest permeation in all skins, suggesting that it could not be permeated in the skin. Furthermore, C14SA and C16SA were less accumulated in delipidized skin compared with normal skin or stripped skin, suggesting that these esters had relatively strong affinities for lipids compared with the other prodrugs in the skin. C16SA showed significantly higher dermal accumulation in all skins compared with its parent salicylic acid. Thus, the palmitoyl oxysalicylate (C16SA) might be a potential candidate for UV protection due to its absence of skin permeation, smaller uptake in the lipid phase and relatively lower skin accumulation.

Investigation into the mechanism by which cyclodextrins influence transdermal drug delivery

The objective of this study was to investigate the mechanism by which hydroxypropyl-beta-cyclodextrin (HPCD) increases transdermal permeation. Hairless mouse skin was pretreated with HPCD solutions for up to 4 h. After removing the HPCD, corticosteroid-containing suspensions were applied and the transdermal flux and skin accumulation of two model drugs were investigated. After pretreatment, changes to the stratum corneum endothermic melting transitions were determined as an indication of HPCD-induced lipid disorganization. Results demonstrated that HPCD pretreatment had no significant effect on the transdermal permeation or skin accumulation of the model corticosteroids. These findings suggest that HPCD functions to enhance the apparent solubility of the drug in the formulation, thus increasing transdermal permeation rather than extracting lipids from the skin.

Benzophenone 4: an emerging allergen in cosmetics and toiletries?

Chemical ultraviolet (UV) filters have, over the last few decades, been increasingly used not only in conventional sunscreen products but also in many cosmetics and toiletries. Allergic contact dermatitis as well as photoallergic contact dermatitis reactions have been well documented as a consequence of such use. Over a 3-year period, we recorded the number of positive patch test reactions to a selection of chemical UV filters that we added to our usual cosmetics/facial series. Our objective was to investigate whether any of these filters produced significant numbers of positive patch test results in the absence of photostimulation. Our results show that not only did benzophenone 4 (2-hydroxy-4-methoxybenzophenone-5-sulphonic acid: sulisobenzone) produce significantly more positive patch test results than the other UV filters that were tested, but also it was the third most frequently positive result overall. Our findings would support the inclusion of benzophenone 4 when patch testing to investigate likely contact dermatitis from cosmetics and toiletries.

Transdermal absorption of the herbicide 2,4-dichlorophenoxyacetic acid is enhanced by both ethanol consumption and sunscreen application

Xenobiotics absorption is a health concern and skin is a major exposure site for many of these chemicals. Both alcohol consumption and topical sunscreen application act as transdermal penetration enhancers for model xenobiotics. The effect of combining these two treatments on transdermal absorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was therefore examined. Skin from rats ingesting low (1.5 g/kg) medium (4.3 g/kg) or high (6 g/kg) ethanol doses or saline control was treated with a commercially available sunscreen containing titanium dioxide and octyl methoxycinnimate and transdermal absorption of 2,4-D was monitored. Ethanol increased penetration by a factor of 1.9, 2.0 and 2.5 for animals treated with 1.5, 4.3 and 6 g/kg respectively, demonstrating an ethanol-induced dose response. Sunscreen application to skin from ethanol gavaged rats caused 2,4-D absorption above that induced by ethanol alone by an additional factor of 1.3, 2.1 and 2.9 for 1.5, 4.3 and 6 g/kg respectively. Comparing 2,4-D transdermal absorption after exposure to both ethanol and sunscreen with a theoretical value (sum of penetration after ethanol or sunscreen treatment) demonstrates that these two treatments enhance additively at the higher doses tested. Results of this study emphasize the importance of limiting excessive alcohol consumption in individuals with potential herbicide exposure rather than discouraging the use of sunscreens, since the consequences of UV-induced skin cancer are far more series than the risks that would be associated with observed increases in chemical exposure.

A liquid chromatography–fluorimetric method for the in vitro estimation of the skin penetration of disodium phenyldibenzimidazole tetrasulfonate from sunscreen formulations through human skin

Disodium phenyldibenzimidazole tetrasulfonate (PDT) is a new organic UV filter with hydrophilic properties used in modern sunscreen spray formulations. The aim of this work was to develop and validate an analytical method that can be used to study skin absorption of PDT from sunscreens. Results obtained in vitro for human skin showed a low level of absorption. The proposed in vitro method employs a diffusion cell. Sunscreen lotion was applied onto pretreated human skin, which was then placed in the cell. PDT was collected in a receptor liquid, the surface of which was in contact with the skin. The solutions obtained were diluted appropriately and analyzed by liquid chromatography without any interference. The analytical features of chromatographic determination with fluorimetic detection were suited to this analytical problem, since this method gave a limit of detection of 1 ng ml(-1). Phenol red (PR) was used as a marker to check the skin integrity, and a sensitive method based on sequential injection on-line solid-phase extraction coupled with spectrophotometric detection was developed for determining this marker in the receptor liquid in order to screen the cells.

Human Safety and Efficacy of Ultraviolet Filters and Sunscreen Products

Ultraviolet (UV) filters are the active ingredients in sunscreens. The concentration and combination of UV filters determine the efficacy of sunscreens as measured by sun protection factor. The safety of individual UV filters, and, more generally, sunscreen products, is a matter of a few related components: objective toxicologic evaluation, phototoxicologic potential, and human health consequences of using products that may reduce some but not all of the solar UV. Of 16 UV filters approved by the US Food and Drug Administration, 9 are used in different combinations in the most currently marketed sunscreens. Most of these compounds are considered safe and effective alone or in combination with other UV filters based on extensive toxicologic/phototoxicologic evaluations and market history. The benefits from proper use of sunscreens outweigh real or perceived human health concerns, establishing a favorable benefit-to-risk ratio. Future UV filters will require complete human safety evaluations alone and in combination with select benchmark ingredients.

A noninvasive objective measure of sunscreen use and reapplication

OBJECTIVES

To study whether a noninvasive swabbing technique can detect sunscreen use for up to 6 hours, and whether the technique can detect reapplication of sunscreen.

METHODS

Thirty volunteer office workers were randomly assigned to have one of a variety of sunscreens applied using recommended application techniques, and half were randomly assigned to have sunscreen reapplied after 3 hours. Alcohol-based swabs were used to obtain a sample from participants' arm at 20 minutes, and hourly from 1 to 6 hours post-application. Absorption readings were analyzed using an UV-visible spectrophotometer.

RESULTS

The swabbing technique was consistently able to distinguish the sunscreen from control swabs for up to 6 hours. The absorption readings between 20 minutes and 6 hours were significantly higher than control swabs. There were no differences between the group that had sunscreen reapplied and the group that did not.

CONCLUSION

The sunscreen swabbing technique is an effective noninvasive method for detecting a variety of sunscreen products in adults over a 6-hour period. No differences in absorption readings were found with sunscreen reapplication. This procedure will be a useful adjunct to other objective measures of sun protection and UV radiation exposure, resulting in a more accurate picture of the sun protection habits of individuals.

Liquid chromatographic assay for common sunscreen agents: application to in vivo assessment of skin penetration and systemic absorption in human volunteers

The purpose of the present study was to develop a reverse-phase high-performance liquid chromatographic (HPLC) assay for quantifying four common sunscreen agents, namely 2-hydroxy-4-methoxybenzophenone, 2-ethylhexyl-p-methoxycinnamate, 2-ethylhexylsalicylate (octylsalicylate) and salicylic acid 3,3,5-trimethcyclohexyl ester (homosalate) in a range of biological matrices. This assay was further applied to study the skin penetration and systemic absorption of sunscreen filters after topical application to human volunteers. Separation was achieved utilizing a Symmetry C(18) column with methanol-water as the mobile phase. The assay permits analysis of the sunscreen agents in biological fluids, including bovine serum albumin (BSA) solution, plasma and urine, and in human epidermis. The assay was linear (r2 > 0.99) with minimum detectable limits of 0.8 ng for oxybenzone, 0.3 ng for octylmethoxycinnamate, and 2 ng for homosalate and octylsalicylate. The inter- and intra-day variation for the four sunscreens was less than 3% at the upper end of the linear range and less than 6% at the lower end. Recoveries of sunscreens from plasma, 4% (w/v) BSA solution and epidermal membranes were within the range of 91-104%. Recoveries from urine of the four sunscreens, and oxybenzone with its metabolites were more than 86%. Up to approximately 1% of the applied dose of oxybenzone and its metabolites was detected in the urine. Appreciable amounts were also detected in the stratum corneum through tape stripping. The HPLC assay and extraction procedures developed are sensitive, simple, rapid, accurate and reproducible. Results from the preliminary clinical study demonstrate significant penetration of all sunscreen agents into the skin, and oxybenzone and metabolites across the skin.

Insect repellent [correction of repellant] interactions: sunscreens enhance DEET (N,N-diethyl-m-toluamide) absorption

Toxicology studies are typically performed on single compounds, which we hypothesized would miss adverse synergies from chemical mixtures. This hypothesis was tested using an insect repellant and sunscreens because both groups include known permeation enhancers, with prior pediatric reports of toxicity from highly concentrated DEET (N,N-diethyl-m-toluamide). Using real-time mass spectroscopy in a hairless mouse skin model, we confirmed substantial penetration of a 20% DEET standard. Despite a lower (10%) DEET content, a commercially marketed sunscreen formulation had a 6-fold more rapid detection (5 versus 30 min) and 3.4-fold greater penetration at steady state. We also tested the efficacy of DEET microemulsion products and confirmed that one successfully slowed the onset of absorption, but not the steady-state permeation. Risks from mixtures of potential toxins are worthy of routine testing, which can be accomplished by simple assays, and are of utmost importance for pediatric applications.

Influence of encapsulation on the in vitro percutaneous absorption of octyl methoxycinnamate

The purpose of this study was to evaluate the in vitro transdermal permeation and skin accumulation of one ultraviolet (UV) absorber-octyl methoxycinnamate (OMC)-through pig skin and to determine the quantity of OMC in the skin surface and different pig skin layers (stratum corneum, viable epidermis, dermis, and receptor fluid). Four cases have been considered: the application of oil-in-water (O/W) and water-in-oil (W/O) emulsions containing the same filter free and encapsulated in nanocapsules (NC). The influence of the carrier on the percutaneous penetration was studied. Data showed that UV absorber exhibited increases in skin accumulation when is formulated in emulsions in free form. Skin accumulation of OMC-free in the emulsions was significantly (P < 0.05) greater than that of OMC-encapsulated for all formulations investigated. OMC-free skin accumulation ranged from 127.8 +/- 22.8 microg/cm(2) (O/W emulsion) to 172.1 +/- 12.9 microg/cm(2) (W/O emulsion). OMC-encapsulated skin accumulation ranged from 50.3 +/- 13.1 microg/cm(2) to 43.0 +/- 6.5 microg/cm(2) at NC-O/W and NC-W/O, respectively. No significant differences were found in the transdermal permeation of cinnamate for any of the formulations tested. The results of this study demonstrate that the inclusion of OMC-encapsulated in sunscreen formulations decreases the skin accumulation of the cinnamate since the in vitro release mechanism of OMC-nanocapsules is governed by hydrophobicity and crystallinity of the polymer and by the high lipophilicity of the drug. The crystallinity of the polymer have the ability of reflecting and scattering UV radiation on their own thus leading to photoprotection without the need for molecular sunscreens.

Topical and systemic photoprotection

Sunscreens are a valuable method of sun protection. Several new compounds are now available. It is important to remember, however, that photoprotection includes more than the use of sunscreens. There are a number of sun-protective behaviors that people can use to decrease their exposure to ultraviolet (UV) radiation. Dermatologists and other health professionals can work toward changing public policy, greatly increasing the ability of people to access shade. In addition, there is growing evidence about the effectiveness of other sun-protective agents. The only systemic medication for sun protection is beta-carotene, which is effective in erythropoietic protoporphyria (EPP).