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Background: Safety-in-use (SIU) studies are commonly used by the cosmetic Industry to confirm the skin and ocular compatibility of cosmetic products under realistic in-use conditions. There are only limited case studies published about the design, outcome and interpretation of product SIU studies., Objective: A series of SIU case studies is presented to demonstrate the considerations in study design and how the methodology can help in supporting skin and ocular safety profile of facial cosmetic products within a population of different ethnicities with normal and self-perceived sensitive skin., Subjects/methods: In a series of four single-blinded SIU studies, more than 250 female study subjects of different ethnicities and with normal and self-assessed sensitive skin were asked to use different facial cosmetic products including lotions, essences and cleansers according to the instructed usage conditions of these products. Each study was specifically designed according to product usage scenarios and target consumer groups. The primary measures of safety were based on dermal evaluations by a dermatologist for erythema and dryness/scaling and by an ophthalmologist for any visible signs of an ocular condition on eyelids, conjunctivae and cornea. The study subjects were also asked for any self-perceived skin or eye reactions. Dermal and ocular irritation potential of the products under realistic product usage conditions was evaluated according to the measures., Results: Across all studies, objectively and self-assessed mean scores for skin and eye effects did not indicate any cumulative response of the investigated products over the study period., Conclusions: As a suitable tool for assessing and establishing the skin and eye compatibility of facial cosmetic products, SIU studies can be designed according to specific consumer groups, skin types and product usage scenarios to better predict realistic in-use conditions. It can demonstrate the safe use of the investigated products for people of different ethnicities, skin types and with normal or self-assessed sensitive skin, single product use or regimen use. The test results are consistent with the inherently low irritation potential of the products., (© 2024 Society of Cosmetic Scientists and Societe Francaise de Cosmetologie.)

A nationwide online survey assessed claimed usage of sunscreen products in 2283 self-identified regular sun protection factor (SPF) consumers (RSPFC) in the United States. Subjects applied sunscreen most frequently when spending more than 3 h in the sun. Sunscreen usage peaks during the summer, with sunny weather prompting 99% usage of beach/recreational SPF products but drops to approximately 50% and 30% on partly cloudy and cloudy days, respectively, regardless of SPF product category. About half of RSPFC augment sunscreen product usage by limiting time in the sun and wearing a hat. SPF products are not reapplied by approximately 20-60% of RSPFC, depending upon product category, and reapplication was less than 33% on cloudy and partly cloudy days. Primary reasons for reapplication were water exposure, number of hours in the sun, and being active/sweating, most notably for beach/recreational SPF products. Importantly, in children, 45% of parents reported "redness" as a signal for reapplying sunscreen product. Only 10% of respondents correctly identified sunscreen products as drugs. Based on these results, while sunscreens may share common ingredients and efficacy measures, their usage by consumers varies widely depending on product type, season, weather, gender, age, and geographical location., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Sunscreen products are composed of ultraviolet (UV) filters and formulated to reduce exposure to sunlight thereby lessening skin damage. Concerns have been raised regarding the toxicity and potential endocrine disrupting (ED) effects of UV filters. The ToxCast/Tox21 program, that is, CompTox, is a high-throughput in vitro screening database of chemicals that identify adverse outcome pathways, key events, and ED potential of chemicals. Using the ToxCast/Tox21 database, octisalate, homosalate, octocrylene, oxybenzone, octinoxate, and avobenzone, 6 commonly used organic UV filters, were found to have been evaluated. These UV filters showed low potency in these bioassays with most activity detected above the range of the cytotoxic burst. The pathways that were most affected were the cell cycle and the nuclear receptor pathways. Most activity was observed in liver and kidney-based bioassays. These organic filters and their metabolites showed relatively weak ED activity when tested in bioassays measuring estrogen receptor (ER), androgen receptor (AR), thyroid receptor, and steroidogenesis activity. Except for oxybenzone, all activity in the endocrine assays occurred at concentrations greater than the cytotoxic burst. Moreover, except for oxybenzone, plasma concentrations (Cmax) measured in humans were at least 100× lower than bioactive (AC50/ACC) concentrations that produced a response in ToxCast/Tox21 assays. These data are consistent with in vivo animal/human studies showing weak or negligible endocrine activity. In sum, when considered as part of a weight-of-evidence assessment and compared with measured plasma concentrations, the results show these organic UV filters have low intrinsic biological activity and risk of toxicity including endocrine disruption in humans., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Society of Toxicology.)

Skin cancer continues to increase in incidence year-on-year and represents the most common form of cancer across the globe. Every human undergoes premature ageing, particularly on the face, neck and hands. Both phenomena are driven primarily by chronic, daily exposure to solar ultraviolet radiation (UVR). While sunscreen products play a primary role in the prevention of UVR skin damage, the active ingredients, i.e., UVR filters, are facing unprecedented challenges in the coming 10 years and their future is by no means certain. This article, therefore, reviews afresh the facts around photoprotection and the role of sunscreen products in the prevention of acute (sunburn) and chronic (cancer, photoageing) skin damage and compares/contrasts these with various emerging questions and opinions around UVR filter technology. We present a passionate defence of this remarkable technology, but also attempt to imagine a world without it., (© 2023 Procter & Gamble. International Journal of Cosmetic Science published by John Wiley & Sons Ltd on behalf of Society of Cosmetic Scientists and Societe Francaise de Cosmetologie.)

Background and Objectives: Home-use intense pulsed light (IPL) hair removal devices are convenient for consumers. Consumer safety associated with home-use IPL devices, however, remains a subject of interest. In this descriptive analysis, we assessed the most commonly reported adverse events (AEs) for a home-use IPL device from postmarketing surveillance and qualitatively compared these with AEs from clinical studies and medical device reports of home-use IPL treatments., Materials and Methods: For this analysis of voluntary reports, we queried a distributor's postmarketing database for IPL devices for the period beginning January 1, 2016, to December 31, 2021. All sources of comments, for example, phone, e-mail, company-sponsored web sites, were included in the analysis. AE data were coded according to the Medical Dictionary for Regulatory Activities (MedDRA) terminology. Also, we conducted a PubMed search to identify AE profiles from existing literature on home-use IPL devices and we searched the Manufacturer and User Facility Device Experience (MAUDE) database for reports on home-use IPL devices. These results were qualitatively compared to the data in the postmarketing surveillance database., Results: A total of 1692 cases involving IPL were identified from voluntary reports of AEs between 2016 and 2021. The shipment-adjusted reporting rate for AE cases (number of AE cases/100,000 shipped IPL devices) was 67/100,000 during this 6-year period. The most commonly reported AEs were pain of skin 27.8% (470/1692), "thermal burn" 18.7% (316/1692), and erythema 16.0% (271/1692). Among the top 25 AEs reported, no unexpected health events were observed. The reported AEs were qualitatively similar to the pattern seen in clinical studies and the MAUDE database associated with such home-use IPL treatments., Conclusion: This is the first such report documenting AEs for home-use IPL hair removal from a postmarketing surveillance program. These data are supportive of the safety of such home-use low-fluence IPL technology., (© 2023 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC.)

The phototoxic potential of a number of furocoumarins is well established. On the other hand, studies have shown that bergamottin, a furocoumarin containing a bulky, hydrophobic side chain, has significantly less or is even absent of phototoxicity potential. The OECD Test Guideline 432 3T3/Neutral Red Uptake (NRU) in vitro phototoxicity test has shown to be a highly predictive test for identifying compounds that exhibit no phototoxicological potential. In this study using OECD 432, the established phototoxic furocoumarin 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP) and psoralen were phototoxic, whereas bergamottin showed no phototoxic potential. When compared to 5-MOP, 8-MOP and psoralen, bergamottin was clearly negative at molar-adjusted concentrations that were more than 9 times higher than those that produced phototoxicity in 8-MOP; nearly 16 times than those for psoralen and more than 36 times higher than those for 5-MOP. These data using in vitro 3T3 NRU Phototoxicity Test (OECD 432) are supportive of earlier studies showing bergamottin does not exhibit phototoxicological properties. The detection and quantification of bergamottin should therefore not contribute to the potential marker furocoumarins for risk management interventions intended to reduce the phototoxicity of natural furocoumarin containing preparations., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Magalie Cluzel reports financial support was provided by LVMH Recherche. Gaelle Hais reports financial support was provided by LVMH Recherche. Veronique Lenouvel reports financial support was provided by LVMH Recherche. Christophe Penichot reports financial support was provided by LVMH Recherche. Celine Sauvage reports financial support was provided by LVMH Recherche. Nicolas Wolf reports financial support was provided by LVMH Recherche. Amaia Irizar reports financial support was provided by The International Fragrance Association. Magalie Cluzel reports a relationship with LVMH Recherche that includes: employment. Gaelle Hais reports a relationship with LVMH Recherche that includes: employment. Amaia Irizar reports a relationship with The International Fragrance Association that includes: consulting or advisory. Veronique Lenouvel reports a relationship with LVMH Recherche that includes: employment. J. Frank Nash reports a relationship with The Procter & Gamble Company that includes: employment. Christophe Penichot reports a relationship with LVMH Recherche that includes: employment. Celine Sauvage reports a relationship with LVMH Recherche that includes: employment. Matthias Vey reports a relationship with The International Fragrance Association that includes: employment. Nicolas Wolf reports a relationship with LVMH Recherche that includes: employment., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The broad spectrum antimicrobial/antifungal zinc pyrithione (ZnPT) is used in products ranging from antifouling paint to antidandruff shampoo. The hazard profile of ZnPT was established based upon comprehensive toxicological testing, and products containing this biocide have been safely used for years. The purpose of this study was to create a dermal physiologically based pharmacokinetic (PBPK) model for ZnPT in the rat for improving dose-response analysis of ZnPT-induced toxicity where reversible hindlimb weakness was the endpoint used as the basis for ZnPT risk assessments. Previously, we developed a PBPK model which simulated the kinetics of pyrithione (PT) and its major metabolites 2-(methylsulfonyl)pyridine and S-glucuronide conjugates in blood and tissues of rats following oral ZnPT administration. The dermal model was optimized utilizing in vitro dermal penetration investigations conducted with rat skin and with historical data from a dermal repeat dose study using rats. The model replicated the observed temporal patterns and elimination kinetics of [ 14 C]PT equivalents in blood and urine during and following repeated dermal dosing and replicated the observed dose-dependencies of absorption, blood [ 14 C]PT equivalents and plasma PT concentrations. The model provided internal dosimetry predictions for a benchmark dose analysis of hindlimb weakness in rats that combined dermal, gavage and dietary studies into a single internal dose-response model with area-under-the-curve (AUC) for plasma PT, the toxic moiety in the rat, as the internal dose metric. This PBPK model has predictive validity for calculating internal doses of PT and/or [ 14 C]PT equivalents from different routes of exposure in the rat.

Pyrithione glucuronide (PTG) and 2-thiopyridine glucuronide (ThPG) have been reported to be the major urinary metabolites in multiple animal species following administration of zinc pyrithione (ZnPT). However, the formation of these metabolites has never been confirmed in humans. A simple and rugged ultra-high-performance liquid chromatography high resolution mass spectrometry (UHPLC-MS/HRMS) method was developed and validated for the quantification of PTG and ThPG to investigate human metabolism of pyrithione following topical application of ZnPT as a shampoo. A UHPLC-MS/HRMS method was required due to the matrix interferences that were observed with the typical industry standard HPLC/tandem mass spectrometry (LC-MS/MS) methodology based on nominal mass triple quadrupole (QQQ) platform approach. Using UPLC-MS/HRMS, both PTG and ThPG were identified in human urine following topical application of ZnPT. The presence of these human urinary metabolites of pyrithione are consistent with findings from earlier studies in multiple animal species and suggest the metabolism of pyrithione is similar amongst those mammalian species studied., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The induction of vomiting by activation of mechanisms protecting the body against ingested toxins is not confined to natural products but can occur in response to manmade medicinal and non-medicinal products such as liquid cleaning products where it is a commonly reported adverse effect of accidental ingestion. The present study examined the utility of an historic database (>30 years old) reporting emetic effects of 98 orally administered liquid cleaning formulations studied in vivo (canine model) to objectively identify the main pro-emetic constituents and to derive a predictive model. Data were analysed by categorizing the formulation constituents into 10 main groups followed by using multivariate correlation, partial least squares and recursive partitioning analysis. Using the ED 50 we objectively identified high ionic strength, non-ionic surfactants (alcohol ethoxylate) and alkaline pH as the main pro-emetic factors. Additionally, a mathematical model was developed which allows prediction of the ED 50 based on formulation. The limitations of the use of historic data and the model are discussed. The results have practical applications in new product formulation and safety but additionally the principles underpinning this in silico study have wider applicability in demonstrating the potential utility of such archival data in current research contributing to animal replacement., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Accidental ingestion of household cleaning products frequently results in emesis but the physicochemical properties responsible are not known. To investigate whether data collected during in vivo animal studies performed >30 years ago could provide novel insights into the components responsible, we re-analysed original studies from a total of 74 liquid cleaning formulations. The incidence of emesis was dose-related with ED 50 values between 0.012 and 8.4 ml/kg and 57% of formulations having an ED 50  ≤ 1 ml/kg. The median latency for emesis was 10.0 min (95% CI, 8-12 min) and number of vomits in 60 min ranged from 1 to 10 (median 2). From the ED 100 , latency and number of vomits we derived a "vomiting index" (VI) for a subset of 15 formulations which revealed an association between a high VI, a high percentage of non-ionic surfactants/high ionic strength, and a pH of ~10 which we propose are causally linked with the possible mechanism(s) discussed. The limitations of using historic data are discussed but analysis of such data has provided novel insights into the emetic characteristics of this class of products and has informed the development of an in silico model to predict the emetic liability of novel formulations without additional in vivo studies., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Identifying chemicals with narcotic potency is an important aspect of assessing the safety of consumer products that may be accidentally ingested. A rapid and efficient assay of narcotic potency is desired for assessing chemicals with such suspected activity., Objectives: This purpose of this research was to develop a non-mammalian vertebrate, high throughput, neurobehavioral method to assess the narcotic potency of chemicals using larval zebrafish., Methods: Larval zebrafish were acutely exposed to chemicals beginning at 5 days post fertilization (5 dpf). Locomotor activity, elicited by regular, periodic photostimulation, was quantified using a video tracking apparatus. Narcotic potency was determined as the molar concentration at which photostimulated locomotor activity was reduced by 50% (IC 50 ). Toxicity was assessed based on observations of morbidity or mortality. Recovery was assessed following removal of test material by serial dilution and reassessment of photostimulated behavior 24 hr later (6 dpf)., Results: A total of 21 chemicals were assessed. Etomidate, a human narcotic analgesic agent, was used as a reference material. Investigating a series of eleven linear, primary alcohols (C6 to C16), a relationship between narcotic potency and carbon number was observed; narcotic potency increased with carbon number up to C12, consistent with historical studies. For a set of technical grade surfactants, nonionic surfactants (i.e., alcohol ethoxylates) were observed to be narcotic agents while anionic surfactants produced evidence of reduced locomotor activity only in combination with toxicity. Of the solvents evaluated, only ethanol exhibited narcotic activity with an IC 50 of 261 mM and was the least potent of the chemicals investigated. Etomidate was the most potent material evaluated with an IC 50 of 0.39 μM., Conclusions: The larval zebrafish neurobehavioral assay provides a method capable of estimating the narcotic potency of chemicals and can identify if toxicity contributes to observed neurobehavioral effects in the test organism., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Zinc pyrithione (ZnPT) is deposited on the skin as a fine particulate and must reach microorganisms localized in the stratum corneum and hair follicles in molecular form to exert its broad-spectrum antimicrobial/antifungal activity. Dissolution of ZnPT particles followed by molecular speciation results in the organic portion, i.e. pyrithione, being more susceptible to skin penetration than the inorganic component, i.e. zinc, or the chelate itself, i.e. ZnPT., Objectives: To further test the hypothesis that ZnPT skin penetration is rate-limited by dissolution and molecular speciation, the effect of different formulations and artificial sebum on the in vitro percutaneous absorption of radiolabel associated with Zn[14C]PT was investigated., Method: In vitro penetration of [14C]PT into and through excised human skin was measured following application of Zn[14C]PT prepared as suspensions in distinct vehicles including water-based carboxymethylcellulose (CMC), diluted body wash comprised of surfactants, and castor oil, in the presence and absence of artificial sebum., Results: The steady-state flux and cumulative absorption of Zn[14C]PT increased 4- to 5-fold when deposited from a body wash or castor oil compared to a water-based CMC suspension. Tritiated water flux measured before and after treatment showed that neither the surfactant vehicle nor castor oil significantly altered barrier function versus water alone. An artificial sebum layer on the skin potentiated Zn[14C]PT and 3H2O absorption when dosed from both aqueous formulations, but not from castor oil., Conclusion: These data are consistent with the hypothesis that ZnPT percutaneous absorption, as measured by [14C]PT kinetics, is controlled by particle dissolution and molecular speciation., (© 2019 S. Karger AG, Basel.)

The broad-spectrum antimicrobial zinc pyrithione (ZnPT) is used in numerous products ranging from in-can preservative/mildicide in paints to antidandruff shampoo. Although products containing ZnPT have a long history of safe use, regulatory agencies routinely set limits of exposure based upon toxicological considerations. The objective of this study was to create a physiologically based pharmacokinetic (PBPK) model for ZnPT in the rat for improving dose-response analysis of ZnPT-induced toxicity, reversible hindlimb weakness, the endpoint that has been used as the basis for ZnPT risk assessments. A rat oral PBPK model was developed that includes compartments for plasma, liver, kidneys, muscle, brain, and rapidly and slowly perfused tissues. Pyrithione metabolism to 2-(methylsulfonyl)pyridine (MSP) and glucuronide conjugates was incorporated into the model. The model was parameterized and optimized based upon data from single-dose intravenous (iv) and oral gavage pharmacokinetic studies of radiolabeled pyrithione ([ 14 C]PT) administered as zinc [ 14 C]-pyrithione (Zn-[ 14 C]PT) to adult female rats. It was further evaluated and refined using data from repeated, multidose oral gavage and dietary studies of Zn[ 14 C]PT in the adult female rat that included measurements of plasma PT concentration, the putative toxic species. The model replicated the observed short-term elimination kinetics of PT in plasma and [ 14 C]PT in whole blood following single doses and longer term temporal patterns of plasma and blood concentrations during repeated dosing schedules. The model also accounted for production and rapid elimination of S-glucuronide conjugates (SG) of 2-pyridinethiol and 2-pyridinethiol-1-oxide in urine, as well as production and slower elimination of MSP, the major [ 14 C]PT species in blood within several hours following administration of ZnPT. The model provided internal dosimetry predictions for a benchmark dose (BMD) analysis of hindlimb weakness in rats, and was used to combine gavage and dietary studies into a single internal dose-response model with area under the curve (AUC) for plasma PT as the internal dose metric. This PBPK model has predictive validity for calculating internal doses of PT and/or [ 14 C]PT from different routes of exposure in the rat.

Background and Objective: Intense pulsed light (IPL) is a mainstream treatment for hair removal. Side effects after IPL are known, but risk factors remain to be investigated. The objective of this study was to assess the contribution of skin pigmentation, fluence level, and ultraviolet radiation (UVR) on IPL-induced side effects., Methods: The study was a blinded, randomized intra-individual controlled trial including 16 healthy subjects with Fitzpatrick Skin Types (FST) II-V. Three test areas were each divided into four sites, randomized to a single IPL exposure of 22, 34, 46 J/cm 2 or triple stacking of 46 J/cm 2 . Areas were subsequently randomized to no UVR or single solar-simulated UVR exposure of 3 Standard Erythema Dose at 30 minutes or 24 hours after IPL. Each area had a corresponding control, resulting in 15 treatment sites. Follow-up visits were scheduled up to 4 weeks after IPL. Outcome measures were: (i) blinded clinical skin reactions; (ii) objectively measured erythema and pigmentation; (iii) pain measured by visual analog scale (VAS); (iv) histology (H&E, Fontana-Masson); and (v) mRNA-expression of p53., Results: Fifteen subjects with FST II-IV completed the protocol. IPL induced a wide range of skin reactions, including erythema (87% of subjects), purpura (27%), blisters (20%), edema (13%), crusting (13%), hyper- (60%), and hypopigmentation (20%). Darker skin pigmentation and increasing IPL fluence were determinants for IPL-induced side effects (P ≤ 0.002), while a single exposure of UVR did not exacerbate side effects (P ≥ 0.180). Clinical findings were confirmed objectively by reflectance spectrometry and qualitatively by histological changes in skin architecture, inflammatory infiltration, and pigmentation. Marker of cellular DNA damage, that is, p53, did not increase after IPL (P ≥ 0.24)., Conclusions: Skin pigmentation and IPL fluence are major determinants of side effects after IPL exposure, while a single exposure to three SED of UVR at 30 minutes or 24 hours after IPL, does not amplify such side effects. Lasers Surg. Med. 49:88-96, 2017. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

A quantitative human risk assessment of chloroxylenol was conducted for liquid hand and dishwashing soap products used by consumers and health-care workers. The toxicological data for chloroxylenol indicate lack of genotoxicity, no evidence of carcinogenicity, and minimal systemic toxicity. No observed adverse effect levels (NOAEL) were established from chronic toxicity studies, specifically a carcinogenicity study that found no cancer excess (18 mg/kg-day) and studies of developmental and reproductive toxicity (100 mg/kg-day). Exposure to chloroxylenol for adults and children was estimated for two types of rinse-off cleaning products, one liquid hand soap, and two dishwashing products. The identified NOAELs were used together with exposure estimates to derive margin of exposure (MOE) estimates for chloroxylenol (i.e., estimates of exposure over NOAELs). These estimates were designed with conservative assumptions and likely overestimate exposure and risk (i.e., highest frequency, 100% dermal penetration). The resulting MOEs ranged from 178 to over 100, 000, 000 indicating negligibly small potential for harm related to consumer or health-care worker exposure to chloroxylenol in liquid soaps used in dish washing and hand washing., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The prevailing advice is to avoid sun exposure after intense pulsed light (IPL) hair removal. However, no systematic evaluation of ultraviolet radiation (UVR) after IPL hair removal exits. Therefore, we investigated the occurrence of side effects in subjects receiving solar-simulated UVR after a low-fluence IPL treatment with a home-use device. Sixteen subjects with Fitzpatrick skin types (FST) II-V were enrolled. Three constitutive buttock blocks (4.4 × 6.4 cm) were each subdivided into four sites, randomized to one IPL exposure of 0, 7, 8, or 10 J/cm2 (spectral output 530-1100 nm). Blocks were randomized to no UVR or three standard erythema doses (SEDs) UVR either 30 min or 24 h after IPL. Follow-up visits were 48 h, 1 week, and 4 weeks after IPL. Outcome measures were (i) clinical skin reactions, (ii) reflectance measurements of erythema and pigmentation, and (iii) pain. Subjects with FST II-IV experienced no skin reactions up to 4 weeks after IPL, neither erythema, edema, blisters, crusting, textual, nor pigment changes. Reflectance confirmed no change in erythema and pigmentation (p ≥ 0.090). UVR exposure induced erythema and increased pigmentation. The combination of IPL and UVR induced skin reactions not different to responses from UVR (IPL-UVR vs. UVR, p ≥ 0.164). Pain was generally low (median 1, range 0-4) and correlated positively with fluence and pigmentation (Spearman's rho ≥ 0.394, p < 0.001). One subject with FST V experienced perifollicular hyperpigmentation after IPL and slightly more intense when exposed to UVR. A single UVR exposure of three SEDs either shortly or 1 day after low-fluence IPL causes no amplification of skin responses in constitutive skin of individuals with FST II-IV.

Realistic estimates of chemical aggregate exposure are needed to ensure consumer safety. As exposure estimates are a critical part of the equation used to calculate acceptable "safe levels" and conduct quantitative risk assessments, methods are needed to produce realistic exposure estimations. To this end, a probabilistic aggregate exposure model was developed to estimate consumer exposure from several rinse off personal cleansing products containing the anti-dandruff preservative zinc pyrithione. The model incorporates large habits and practices surveys, containing data on frequency of use, amount applied, co-use along with market share, and combines these data at the level of the individual based on subject demographics to better estimate exposure. The daily-applied exposure (i.e., amount applied to the skin) was 3.79 mg/kg/day for the 95th percentile consumer. The estimated internal dose for the 95th percentile exposure ranged from 0.01-1.29 μg/kg/day after accounting for retention following rinsing and dermal penetration of ZnPt. This probabilistic aggregate exposure model can be used in the human safety assessment of ingredients in multiple rinse-off technologies (e.g., shampoo, bar soap, body wash, and liquid hand soap). In addition, this model may be used in other situations where refined exposure assessment is required to support a chemical risk assessment., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background: At-home laser and intense pulsed-light hair removal continues to grow in popularity and availability. A relatively limited body of evidence is available on the course of hair growth during and after low-fluence laser usage., Objectives: To assess growing hair counts, thickness and colour quantitatively during and after cessation of low-fluence laser treatment., Methods: Thirty-six women with skin phototypes I-IV and light to dark-brown axillary hairs were included. Entire axillary regions were randomized to zero or eight self-administered weekly treatments with an 810-nm home-use laser at 5·0-6·4 J cm(-2). Standardized clinical photographs were taken before each treatment and up to 3 months after the final treatment for computer-aided quantification of growing hair counts, thickness and colour., Results: Thirty-two women completed the study protocol. During sustained treatment, there was a reduction in growing hair that reached a plateau of up to 59%, while remaining hairs became up to 38% thinner and 5% lighter (P < 0·001). The majority of subjects (77%) reported 'moderately' to 'much less hair' in treated than untreated axilla, and assessed remaining hairs as thinner and lighter (≥ 60%). After treatment cessation, hair growth gradually returned to baseline levels, and 3 months after the final treatment the count and thickness of actively growing hair exceeded pretreatment values by 29% and 7%, respectively (P ≤ 0·04)., Conclusions: Sustained usage of low-fluence laser induced a stable reduction of growing hair counts, thickness and colour. The reduction was reversible and hairs regrew beyond baseline values after cessation of usage. Computer-aided image analysis was qualified for quantification of hair counts, thickness and colour after laser epilation., (© 2014 British Association of Dermatologists.)

Photostability or photo-instability of sunscreen products is most often discussed in undesirable terms with respect to human safety. The health risks, specifically associated with sunscreens, photostable or photo-unstable, include phototoxic/photoirritation or photoallergic responses and, longer-term, an increased risk of skin cancers or photoageing. The aims of this paper are to define photostability/photo-instability and objectively assess the acute and chronic toxicological consequences from the human exposure to UV filter/sunscreens and any probable photo-degradation products. The reported prevalence of photoirritation and photoallergic responses to sunscreens is rare compared with adverse events, for example, skin irritation or sensitization, produced by cosmetics or topically applied drugs and do not directly implicate potential photo-degradation products of UV filters. Moreover, for at least one photo-unstable combination, octyl methoxycinnamate and avobenzone, the long-term benefits to humans, i.e., reduction in skin cancers, seem to outweigh any potential adverse consequences attributed to photo-degradation. Sunscreen products are formulated to achieve maximum efficacy which, by necessity and design, incorporate measures to support and promote photostability since all organic UV filters have the potential to photo-degrade. Current performance measures, in vivo SPF and in vitro UVA, conducted under standardized conditions, in part account for photostability. The concerns expressed when considering human exposure to potential photo-unstable UV filters or sunscreen products may not manifest as health risks under conditions of use. Still, improvement in sunscreen product photostability continues to be a key strategic objective for manufacturers., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Excessive exposure from ultraviolet (UV) radiation contributes to the development of skin cancers and photoaging. Topical sunscreen products remain one of the most widely used forms of protection for the majority of the public. The objective of this analysis was to examine photoprotection trends (e.g., SPF value) and the degree of UVA I protection from 1997 to 2009 in the United States. Sunscreen products purchased and evaluated in 1997 (N = 59), 2003 (N = 188) and again in 2009 (N = 330), totaling 577, were included in this analysis. Information regarding (1) the SPF value, (2) name and concentration of the active ingredients, (3) type of products (i.e., daily vs. recreational/beach), and (4) claims of UVA protection was recorded and analyzed. In addition, the critical wavelength (CW) of 330 products from 2009 was determined. The results showed an increase in the SPF values of products from 1997 to 2009. The percentage of low SPF products (SPF 4-14) decreased from 27% in 1997 to 6% in 2009. The number of products containing a known UVA-I filter (i.e., avobenzone or zinc oxide) increased from 5% in 1997 to 70% in 2009. Lastly, approximately, 225 (68%) of the products tested in 2009 attained CW > 370 nm. In the past decade, sunscreen products have undergone fundamental improvements, the most significant of which is the breadth of protection against UVA I.

In society, power is often transferred to another person or group. A previous work studied the evolution of cooperation among robot players through a coalition formation game with a non-cooperative procedure of acceptance of an agency of another player. Motivated by this previous work, we conduct a laboratory experiment on finitely repeated three-person coalition formation games. Human players with different strength according to the coalition payoffs can accept a transfer of power to another player, the agent, who then distributes the coalition payoffs. We find that the agencies method for coalition formation is quite successful in promoting efficiency. However, the agent faces a tension between short-term incentives of not equally distributing the coalition payoff and the long-term concern to keep cooperation going. In a given round, the strong player in our experiment often resolves this tension approximately in line with the Shapley value and the nucleolus. Yet aggregated over all rounds, the payoff differences between players are rather small, and the equal division of payoffs predicts about 80% of all groups best. One reason is that the voting procedure appears to induce a balance of power, independent of the individual player's strength: Selfish subjects tend to be voted out of their agency and are further disciplined by reciprocal behaviors.

This is the report from the "ECVAM-EFPIA workshop on 3T3 NRU Phototoxicity Test: Practical Experience and Implications for Phototoxicity Testing", jointly organized by ECVAM and EFPIA and held on the 25-27 October 2010 in Somma Lombardo, Italy. The European Centre for the Validation of Alternative Methods (ECVAM) was established in 1991 within the European Commission Joint Research, based on a Communication from the European Commission (1991). The main objective of ECVAM is to promote the scientific and regulatory acceptance of alternative methods which are of importance to the biosciences and which reduce, refine and replace the use of laboratory animals. The European Federation of Pharmaceuticals Industries and Association (EFPIA) represent the pharmaceutical industry operating in Europe. Through its direct membership of 31 national associations and 40 leading pharmaceutical companies, EFPIA is the voice on the EU scene of 2200 companies committed to researching, developing and bringing to patients new medicines that improve health and the quality of life around the world. The workshop, co-chaired by Joachim Kreysa (ECVAM) and Phil Wilcox (GSK, EFPIA) involved thirty-five experts from academia, regulatory authorities and industry, invited to contribute with their experiences in the field of phototoxicology. The main objectives of the workshop were: -to present 'in use' experience of the pharmaceutical industry with the 3T3 Neutral Red Uptake Phototoxicity Test (3T3 NRU-PT), -to discuss why it differs from the results in the original validation exercise, -to discuss technical issues and consider ways to improve the usability of the 3T3 NRU-PT for (non-topical) pharmaceuticals, e.g., by modifying the threshold of chemical light absorption to trigger photo-toxicological testing, and by modifying technical aspects of the assay, or adjusting the criteria used to classify a positive response. During the workshop, the assay methodology was reviewed by comparing the OECD Test Guideline (TG 432) with the protocols used in testing laboratories, data from EFPIA and JPMA 'surveys' were presented and possible reasons for the outcomes were discussed. Experts from cosmetics and pharmaceutical industries reported on their experience with the 3T3 NRU-PT and evidence was presented for phototoxic clinical symptoms that could be linked to certain relevant molecules. Brainstorming sessions discussed if the 3T3 NRU-PT needed to be improved and whether alternatives to the 3T3 NRU-PT exist. Finally, the viewpoint from EU and US regulators was presented. In the final session, the conclusions of the meeting were summarized, with action points. It was concluded that the 3T3 NRU-PT identifies phototoxicological hazards with a 100% sensitivity, and thus is accepted as the tier one test that correctly identifies the absence of phototoxic potential. Consequently, positive results in the 3T3 NRU-PT often do not translate into a clinical phototoxicity risk. Possible ways to improve the practical use of this assay include: (i) adaptation of changed UV/vis-absorption criteria as a means to reduce the number of materials tested, (ii) reduction of the highest concentration to be tested, and (iii) consideration of modifying the threshold criteria for the prediction of a positive call in the test., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Hair removal with professional light-based devices is established as an effective, mainstream treatment. The field of optical home-based hair removal is evolving and movement from control by physicians into hands of consumers warrants understanding efficacy and human safety., Objectives: To systematically review and evaluate the efficacy and human safety of currently available home-based optical hair removal devices., Methods: A comprehensive Pub Med literature search was conducted which systematically identified publications of relevance. Prospective clinical trials were included whether controlled, uncontrolled or randomized and with a sample size of at least 10 individuals., Results: We identified a total of seven studies: one controlled (CT) and six uncontrolled trials (UCTs). No randomized controlled trials (RCT) were recognized. The best evidence was found for IPL (intense pulsed light) (three devices, one CT, five UCTs) and limited evidence for laser devices (one diode laser, one UCT). Most studies evaluated short-term hair reduction up to 3 and 6 months following light exposure at different body sites. Hair reduction percentages ranged from 6% to 72% after repetitive treatments. The most frequently reported side-effect was erythema, but oedema, blistering, crusting and pigment changes were also reported. Theoretical concerns about ocular damage and paradoxical hair growth have not been reported in any of the studies reviewed., Conclusions: Available evidence from prospective, uncontrolled clinical trials indicates short-term hair removal efficacy of currently available home-use light-based hair removal devices. Additional controlled trials will be helpful to substantiate the efficacy and to better predict the incidence of adverse events associated with optical home-use hair removal., (© 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.)

Light-based hair removal (LHR) is one of the fastest growing, nonsurgical aesthetic cosmetic procedures in the United States and Europe. A variety of light sources including lasers, e.g. alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), Nd:YAG laser (1064 nm) and broad-spectrum intense pulsed light (IPL, 590-1200 nm), are available and used widely for such procedures in dermatological/clinical settings under proper supervision. Patient selection and appropriate fluence settings are managed by professionals to maximize efficacy while minimizing adverse events. In the past 5 years, LHR devices have been sold directly to consumers for treatment in the home. In this review, we outline the principles underlying laser and IPL technologies and undertake an evidence-based assessment of the short- and long-term efficacy of the different devices available to the practising dermatologist and discuss the efficacy and human safety implications of home-use devices., (© 2011 The Authors. BJD © 2011 British Association of Dermatologists.)

Based on the current weight of evidence of all available data, the risk for humans from the use of nano-structured titanium dioxide (TiO(2)) or zinc oxide (ZnO) currently used in cosmetic preparations or sunscreens is considered negligible. There is a large body of information that when viewed in its entirety is considered as sufficient to demonstrate that these nano-structured ultraviolet (UV) filters, irrespective of various treatments (coatings) or crystalline structure, can be regarded as safe for use at concentrations up to 25% in cosmetic products to protect the skin from harmful effects of solar UV radiation. "Nano" TiO(2) and ZnO formulated in topically applied sunscreen products exist as aggregates of primary particles ranging from 30-150 nm in size. These aggregates are bonded such that the force of sunscreen product application onto the skin would have no impact on their structure or result in the release of primary particles. Multiple studies have shown that under exaggerated test conditions neither nano-structured TiO(2) nor ZnO penetrates beyond the stratum corneum of skin. Further, the distribution and persistence of these nano-structured metal oxides is the same compared to larger pigment-grade (i.e., >100 nm) particles, demonstrating equivalence in the recognition and elimination of such material from the body. Finally, the in vitro genotoxic and photogenotoxic profiles of these nano-structured metal oxides are of no consequence to human health. Whereas the most logical, straightforward conclusion based on data from internationally-recognized guideline studies and current 20+ year history of human use is that nano-structured TiO(2) and ZnO are safe, there will continue to be questions as "nano" conjures images of technology gone awry. Despite this rather sober view, the public health benefits of sunscreens containing nano TiO(2) and/or ZnO outweigh human safety concerns for these UV filters.

Climbazole is an imidazole antifungal agent that can provide anti-dandruff benefits when incorporated into a shampoo matrix. A series of genotoxicity studies were performed to support the human safety of this azole antifungal drug. Climbazole was not mutagenic in the Salmonella typhimurium or Escherichia coli Ames assay and did not induce micronuclei in human lymphocytes. In the mouse lymphoma assay (MLA), climbazole was negative (non-mutagenic) with and without metabolic (S9) activation after a 4 h exposure; an increase in small colony mutants was observed without metabolic activation after a 24 h exposure at concentrations of 15 and 17.5 μg/mL. An in vivo mouse micronucleus test was negative up to a maximum tolerated dose (MTD) of 150 mg/kg climbazole administered orally. In the in vivo/in vitro unscheduled DNA synthesis assay, climbazole showed no evidence of DNA damage in the livers of rats at doses up to the MTD of 200 mg/kg orally. A toxicokinetic study was performed in mice with oral administration of [14C]-climbazole (150 mg/kg). Radioactivity (20.42 μg-equiv./g plasma) was detected 15 min after oral administration of [14C]-climbazole, and the peak concentration was 62.96 μg-equiv./g plasma at 8 h after dosing. The measured amounts of radioactivity in plasma, at all sample times from 15 min up to 24 h, exceeded the concentrations that induced increases in mutation frequency after 24 h exposure of mouse lymphoma cells in vitro (15 and 17.5 μg/mL). These observations lend support to the conclusion that climbazole does not present a genotoxic risk in vivo. Furthermore, these data are consistent with the published data for other azole antifungals that work by preventing the synthesis of ergosterol and, as a class, are generally non-genotoxic, except some isolated positive results of questionable significance. Collectively, these data are supportive of the view that climbazole does not present a genotoxic or carcinogenic risk to humans.

Conceptually, sunscreen products are quite simple. The ultraviolet (UV) filters in these products reduce the "dose" of solar energy to which the skin is exposed. Underlying this empirical notion are many complexities including measures of product efficacy and how to communicate this to consumers. The sun protection factor (SPF) test is and should remain the singular in vivo method for evaluating sunscreens. Additionally, substrate spectrophotometric measure of absorbance/transmittance and the calculation of the summary statistic, such as the critical wavelength (ie, lambda(c)), should be used as a means of evaluating broad-spectrum (ie, UVA) protection. Ideally, the photoprotective efficacy of sunscreen products will be communicated to consumers as an SPF no greater than 50 and a single designation of "broad-spectrum" to indicate long-wavelength UVA protection.

Background: There are considerable data to suggest that protection from solar ultraviolet (UV) radiation will reduce the risk of acute and chronic skin damage in humans. Whereas the sun protection factor (SPF) provides an index of protection against erythemally effective solar UV, largely confined to the UVB (290-320 nm) and short-wavelength UVA (320-340 nm) region, there is currently no agreed-upon method to measure broad-spectrum protection against long-wavelength UVA (340-400 nm)., Objective: The objective of these studies was to assess the potential of in vitro UV substrate spectrophotometry and subsequent calculation of the "critical wavelength" value as a measure of broad-spectrum UV protection and as a routine, practical procedure for classification of sunscreen products., Methods: The spectral absorption of 59 commercially available sunscreen products and multiple experimental formulas with one or more UV filters was measured. Sunscreen product, 1 mg/cm(2), was applied to a hydrated synthetic collagen substrate, preirradiated with a solar simulator, and then subjected to UV substrate spectrophotometry. Multiple determinations from 5 independent samples per product were used to calculate the critical wavelength value, defined as the wavelength at which the integral of the spectral absorbance curve reached 90% of the integral from 290 to 400 nm., Results: We found that a recognized long-wave UVA active ingredient such as titanium dioxide, zinc oxide, or avobenzone is a necessary but insufficient product requirement for achieving the highest proposed broad-spectrum classification, that is, critical wavelength of 370 nm or more. Although SPF and critical wavelength are largely independent of each other, UVA absorbance must increase commensurate with SPF to maintain the same critical wavelength value. Substrate spectrophotometry and the calculation of critical wavelength can readily account for sunscreen photostability by UV preirradiation. Finally, there is also a strong positive relationship between critical wavelength and a currently available in vivo measure of UVA protection., Conclusion: Determination of critical wavelength by means of UV substrate spectrophotometry provides a rapid, inexpensive, and reliable measure of broad-spectrum protection, which is largely independent of SPF, yet ensures long-wavelength UVA protection commensurate with SPF. The procedure provides a routine, sensitive means of differentiating and classifying sunscreen products and, importantly, obviates the need to subject volunteers to acute exposures of high-dose, nonterrestrial UV, the health risks of which are still poorly understood.

Background: Acute and chronic skin damage occurs as a consequence of solar UV radiation exposure. To diminish such skin damage, the dermatologic community advocates the daily use of sunscreens as part of a sun avoidance strategy., Objective: We determined the effectiveness of a sunscreen product with a sunscreen protection factor (SPF) of 15 applied daily in preventing UV-induced histologic damage in human skin compared with the protection afforded by sunscreens with equal or higher SPF applied intermittently., Methods: Twenty-four subjects were exposed to 2 minimal erythema doses of solar-simulated UV on 4 consecutive days. Three sunscreen products were applied to the buttock of each subject. One SPF 15 product was applied daily before exposure to UV and, to simulate intermittent product use, an SPF 15 or SPF 29 product was applied on 3 of 4 days, with one missed application on days 2, 3, or 4. Skin biopsy specimens were taken and processed for routine and immunohistochemical staining. Changes in number of sunburn cells and Langerhans cells as well as degree of inflammatory infiltrate and lysozyme immunostaining were determined., Results: There was a statistically significant increase in the number of sunburn cells, degree of inflammation, and intensity of lysozyme staining, and there was a decrease in the number of Langerhans cells at sites where sunscreen application was missed as compared with unirradiated control and daily SPF 15 sunscreen-treated sites., Conclusion: Our data suggest that daily use of a sunscreen reduces the skin damage produced by UV exposure compared with intermittent use of equal or higher SPF products. The daily application of sunscreens in appropriate quantities reduces the harmful effects of solar UV radiation on skin. Compliance is essential for maximal benefit of sunscreens.

There is substantial evidence that ultraviolet radiation induces the formation of reactive oxygen species which are implicated as toxic intermediates in the pathogenesis of photoaging. The aim of this study was to determine whether repeated topical treatment with benzoyl peroxide, a source of free radicals, produced the same cutaneous effects as chronic ultraviolet B radiation. Three concentrations of benzoyl peroxide (0.1, 1.5, 5.0% wt/wt) and three cumulative fluences of ultraviolet B radiation (0.9, 2.2, 5.1 J per cm2) used alone and in all combinations along with appropriate controls. Female SKH1 (hr/hr) albino hairless mice were treated 5 d per wk for 12 wk. Extracellular matrix molecules and histologic parameters were assessed. Ultraviolet B radiation induced a fluence-dependent and time-dependent increase in skin-fold thickness. Fluence dependence was seen for epidermal thickness, sunburn cell numbers, dermal thickness, glycosaminoglycan content, mast cell numbers, and skin-fold thickness. Benzoyl peroxide treatment alone caused less marked increases in epidermal and dermal measures compared with ultraviolet B under the conditions used. A benzoyl peroxide concentration-dependent increase was only observed for elastin content, although the highest concentration of benzoyl peroxide increased epidermal thickness and glycosaminoglycan content. A synergistic interaction between ultraviolet B and benzoyl peroxide was not found. These results indicate that repeated administration of benzoyl peroxide produces skin changes in the hairless mouse that qualitatively resemble those produced by ultraviolet B and suggest that common mechanisms may be involved. In addition, any potential synergistic effect of ultraviolet B and benzoyl peroxide was below the level of detection used in this study.

The use of sunscreen products has been advocated by many health care practitioners as a means to reduce skin damage produced by ultraviolet radiation (UVR) from sunlight. There is a need to better understand the efficacy and safety of sunscreen products given this ongoing campaign encouraging their use. The approach used to establish sunscreen efficacy, sun protection factor (SPF), is a useful assessment of primarily UVB (290-320 nm) filters. The SPF test, however, does not adequately assess the complete photoprotective profile of sunscreens specifically against long wavelength UVAI (340-400 nm). Moreover, to date, there is no singular, agreed upon method for evaluating UVA efficacy despite the immediate and seemingly urgent consumer need to develop sunscreen products that provide broad-spectrum UVB and UVA photoprotection. With regard to the safety of UVB and UVA filters, the current list of commonly used organic and inorganic sunscreens has favorable toxicological profiles based on acute, subchronic and chronic animal or human studies. Further, in most studies, sunscreens have been shown to prevent the damaging effects of UVR exposure. Thus, based on this review of currently available data, it is concluded that sunscreen ingredients or products do not pose a human health concern. Further, the regular use of appropriate broad-spectrum sunscreen products could have a significant and favorable impact on public health as part of an overall strategy to reduce UVR exposure.

White mineral oils have a long history of safe use by humans in orally ingested and topically applied products. A re-evaluation of the use of certain mineral hydrocarbons in the preparation of food items by regulators in the UK, however, has prompted additional safety studies and a critical assessment of the toxicological effects of white mineral oils. As white mineral oils are present in many topically applied drug and non-drug products, it is of interest to review the toxicological effects of mineral oil produced by this route of exposure. Specifically, the concern regarding the safety of white mineral oils has arisen, in part, from results of subchronic (e.g 90 day) feeding studies that reported the presence of granulomas in liver and histiocytosis in mesenteric lymph nodes of Fischer 344 rats after oral ingestion of select white mineral oils. In contrast to these subchronic oral studies, repeated topical exposure to white mineral oils has not been found to produce liver granulomas, histiocytosis in the mesenteric or other lymph nodes, or any local or systemic toxicity including tumour formation in Fischer 344 rates, C3H mice, New Zealand White rabbits or beagle dogs at similar or higher exposures (mg/kg/day). On the basis of these findings and reports on negligible epidermal penetration of topically applied white mineral oils, there is no evidence of any hazard identified for topical exposure to white mineral oils at any dose in multiple species. This conclusion is supported by the long and uneventful human use of white mineral oils in drug and non-drug topically applied products.

In vivo microdialysis was used to determine whether the 3,4-methylenedioxymethamphetamine (MDMA)-induced release of serotonin (5-HT) in vivo involves a carrier-mediated process and to investigate further the state-dependent interaction between 5-HT and dopamine. MDMA produced a dose-dependent increase in the extracellular concentration of 5-HT in the striatum and prefrontal cortex that was attenuated by treatment with fluoxetine but not by tetrodotoxin. Suppression by fluoxetine of the MDMA-induced release of 5-HT was accompanied by a suppression of the MDMA-induced release of dopamine. Administration of MDMA to rats treated with carbidopa and L-5-hydroxytryptophan resulted in a synergistic elevation of the extracellular concentration of 5-HT that was much greater than that produced by either treatment alone. The MDMA-induced release of dopamine by MDMA also was potentiated in 5-hydroxytryptophan-treated rats. These data are consistent with the view that MDMA increases the extracellular concentration of 5-HT by facilitating carrier-mediated 5-HT release, which can be enhanced greatly under conditions in which 5-HT synthesis is stimulated. Moreover, these data are supportive of a state-dependent, stimulatory role of 5-HT in the regulation of dopamine release.

The effects of the amphetamine analog, 3,4-methylenedioxymethamphetamine (MDMA) were compared to the effects of d-amphetamine on the in vivo release of dopamine and gamma-aminobutyric acid (GABA) in the striatum and substantia nigra. The brain region-dependent role of the 5-HT2 receptors in the striatum and substantia nigra in regulating MDMA-induced dopamine and GABA release also was studied. Changes in the extracellular concentration of dopamine, 5-HT and GABA were measured simultaneously in the awake rat by in vivo microdialysis. The increase in striatal dopamine produced by systemic administration of MDMA was attenuated by infusion of TTX into the striatum. Infusion of the 5-HT2A/2C antagonist ritanserin into the striatum or the ipsilateral substantia nigra also significantly attenuated MDMA-induced dopamine release in the striatum. At the doses used in this study, MDMA but not d-amphetamine increased the extracellular concentrations of 5-HT and decreased GABA efflux in the substantia nigra. The ability of MDMA to decrease nigral GABA efflux also was blocked by the local infusion of ritanserin into either the substantia nigra or the striatum. Overall, these data provide evidence that MDMA increases dopamine release partly through an impulse-mediated mechanism. Furthermore, this increase in striatal dopamine efflux produced by MDMA is regulated, in part, by 5-HT2A/2C receptors in the striatum and the substantia nigra and ultimately by GABAergic input into the substantia nigra.

A method was found to synthesize 1-(2,5-dimethoxy-4-(trifluoromethyl) phenyl)-2-aminopropane, 5, and its des-alpha-methyl congener 2-(2,5-dimethoxy-4-(trifluoromethyl)phenyl)aminoethane, 6, the trifluoromethyl analogs of substituted hallucinogenic phenethylamine derivatives such as 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (3, DOI) that are potent 5-HT2A/2C agonists. In our hands, 5 and 6 have proven to have affinity for [3H]ketanserin or [125I]-3-labeled 5-HT2A/2C sites in rat cortex comparable to or higher than the analogous bromo or iodo analogs. Similarly, 5 and 6 had potency comparable to or slightly greater than that of their bromo or iodo congeners in the two-lever drug discrimination assay in rats trained to discriminate saline from LSD tartrate. The agonist properties of 5 and 6 were evaluated by measuring the accumulation of [3H]inositol monophosphate in cultured cells selectively expressing either 5-HT2A or 5-HT2C receptors. In comparison to serotonin (5-HT), compounds 3 (DOI), 5, and 6 were equally efficacious and full agonists at the 5-HT2C receptor. Similarly, 3 and 5 produced equivalent responses at the 5-HT2A receptor as compared to 5-HT. In contrast, 6, the alpha-desmethyl analog of 5, was only half as potent at stimulating inositol monophosphate accumulation at the 5-HT2A receptor. In conclusion, the title compound 5 and its alpha-desmethyl congener 6 appear to be the most potent of the so-called hallucinogenic amphetamine 5-HT agonists reported to date. Further, the reduced efficacy of 6 at the 5-HT2A receptor may offer at least a partial explanation for the observed higher in vivo potencies of alpha-methyl-substituted compounds in this series.

The effects of the 5-HT2 receptor agonists 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) on 3,4-methylenedioxymethamphetamine (MDMA)-induced dopamine release and 5-HT depletion in the striatum were studied. The MDMA-induced increase in the extracellular concentration of dopamine in the striatum was enhanced significantly in rats treated with either DOI (2 mg/kg, ip.) or 5-MeODMT (15 mg/kg, ip.), as assessed using in vivo microdialysis. Neither DOI nor 5-MeODMT alone altered the extracellular concentration of dopamine in the striatum. The striatal concentration of 5-HT was decreased, but not significantly, 7 days following a single administration of MDMA (10 mg/kg, sc.). However, 7 days following the concomitant treatment with DOI and MDMA the striatal concentration of 5-HT was significantly less than that in rats treated with MDMA alone or the vehicle-treated controls. It is concluded that activation of 5-HT2 receptors is an important determinant of the acute increase in extracellular dopamine and, consequently, the long-term depletion of brain 5-HT produced by MDMA.

The effect of the R(-) and S(+) isomers of 3,4-methylenedioxyamphetamine (MDA) and its N-methyl analog 3,4-methylenedioxymethamphetamine (MDMA) on [3H]inositol monophosphate accumulation was studied in cells expressing either 5-HT2A or 5-HT2C receptors. The isomers of MDA produced a concentration dependent increase in phosphatidyl inositol (PI) hydrolysis at the 5-HT2A receptors, with the R(-) isomer of MDA being more potent than the S(+) at the 5-HT2A receptor. The R(-) and S(+) isomers of MDMA were significantly less efficacious at the 5-HT2A receptor as compared to MDA; S(+)MDMA had no effect. At the 5-HT2C receptor, both R(-) and S(+)MDA were equipotent at stimulating PI hydrolysis, with the S(+) isomer of MDMA being more efficacious at the 5-HT2C receptor compared with the R(-) isomer. In all cases at both the 5-HT2A and 5-HT2C receptors, the affinities of the isomers of MDMA and MDA were at least 2-3 orders of magnitude less than 5-HT. Despite the weak effect of these compounds at the 5-HT2A and 5-HT2C receptors, these substituted amphetamines do possess intrinsic activity which may contribute to their neurotoxic effects when administered at high doses.

A single administration of D-amphetamine and iprindole has been reported to produce selective, long-lasting decreases in brain dopamine (DA) content because of axon terminal degeneration. It has been found that the noncompetitive glutamate (GLU) antagonist, MK 801, blocks D-amphetamine-induced DA depletion in iprindole-treated rats. In the present study, the effect of D-amphetamine (9.2 mg/kg) and iprindole (10 mg/kg) on the extracellular concentrations of DA and GLU was determined in the striatum of awake, freely moving rats by the use of in vivo microdialysis. D-Amphetamine significantly increased DA and GLU efflux in the striatum of iprindole-treated rats as compared to the vehicle-treated group. The increase in the extracellular concentration of GLU occurred 4-6 hr following drug administration. The concentration of DA was decreased significantly in the striatum of D-amphetamine and iprindole-treated rats 7 days following administration as compared to the vehicle-treated group. Inhibition of tyrosine hydroxylase after alpha-methylparatyrosine (150 mg/kg) administration attenuated D-amphetamine-induced DA and GLU release. The DA antagonist, haloperidol (1 mg/kg), blocked D-amphetamine-induced GLU release without affecting the increase in the extracellular concentration of DA produced by the combination of D-amphetamine and iprindole. Both alpha-methylparatyrosine and haloperidol blocked the depletion of DA in the striatum 7 days after D-amphetamine and iprindole as compared to the vehicle group. In addition, administration of MK-801 (2 mg/kg) 2 hr after D-amphetamine significantly attenuated the long-term (7 day) decrease in striatal DA content produced by the combination of D-amphetamine and iprindole.2+

The effect of acute, reversible depletion of either serotonin [5-hydroxytryptamine (5-HT)] or dopamine (DA) on the long-term (7-day) decrease of brain 5-HT content produced after 3,4-methylenedioxymethamphetamine (MDMA) administration was investigated. The tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine (alpha-MPT) significantly attenuated the acute increase in DA efflux produced by MDMA in the striatum as measured by in vivo microdialysis. Treatment with alpha-MPT had no effect on MDMA-induced 5-HT release. alpha-MPT treatment blocked the long-term (7-day) depletion of striatal 5-HT content after MDMA administration. The tryptophan hydroxylase inhibitor p-chlorophenylalanine (PCPA) completely blocked the acute increase in the extracellular concentration of 5-HT produced by MDMA. Although PCPA significantly attenuated the increase in DA efflux produced by MDMA, the effect was small in magnitude. More importantly, treatment with PCPA had no effect on MDMA-induced decrease of 5-HT uptake sites in the frontal cortex. These data are suggestive that acute depletion of DA but not 5-HT protects against the long-term neurotoxic effects of MDMA on 5-HT axon terminals. In addition, these data are supportive of the hypothesis that DA plays a major role in the neurotoxic effects of MDMA.

The effects of two inhibitors of dopamine (DA) reuptake, amfonelic acid and GBR 12909, on the clozapine- and haloperidol-induced increases in DA synthesis, release, and metabolism were investigated in the rat. In the striatum, as well as in the nucleus accumbens, the haloperidol-induced increase in tissue concentrations of dihydroxyphenylacetic acid (DOPAC) or the accumulation of dihydroxyphenylalanine (DOPA) was potentiated or unaltered, respectively, in rats treated with amfonelic acid. In contrast, amfonelic acid attenuated the stimulatory effects of clozapine on DOPAC concentrations and DOPA accumulation in both brain regions. GBR 12909 also differentially affected the haloperidol- and clozapine-induced increases in DOPAC concentrations. However, the clozapine-induced increase in DOPA accumulation in the median eminence was not significantly altered by treatment with amfonelic acid. The haloperidol-induced increase in the extracellular concentrations of DA and DOPAC in the striatum also was potentiated by amfonelic acid, whereas the increase elicited by clozapine was suppressed. The increase in extracellular DA produced by the administration of morphine or the coadministration of ritanserin, a 5-HT2 antagonist, and haloperidol also was potentiated by amfonelic acid. The ability of amfonelic acid to distinguish between the actions of clozapine and haloperidol on nigrostriatal and mesocorticolimbic DA neurons does not appear to be related to differences in the effects of the drugs on DA autoreceptors or 5-HT2 receptors. Moreover, the mechanism through which clozapine activates tuberoinfundibular DA neurons may differ from that which is involved in the activation of nigrostriatal or mesocorticolimbic DA neurons.