In vivo percutaneous absorption of capsaicin,nonivamide and sodium nonivamide acetate from ointment bases: Skin erythema test and non-invasive surface recovery technique in humans

Nonivamide (NVA) and sodium nonivamide acetate (SNA) are both synthetic analogues of capsaicin. In this present study, the in vivo skin erythema test and non-invasive surface recovery techniques were performed in humans for capsaicin, NVA and SNA after transdermal ointment application. In order to quantify the skin erythema and irritation caused by capsaicin and its analogues, laser Doppler flowmetry (LDF) was utilized for determining the cutaneous blood flow to assess the degree of irritant reaction. In the study of surface recovery technique, NVA hydrophilic ointment base showed higher flux and cumulative absorbed amount than the other formulations. In the study of skin erythema test, capsaicin caused severer skin irritation than NVA in humans. Moreover, there was no significant difference between the erythema levels of SNA and control group indicating that SNA produced no skin irritation or pungent sensation. In addition, increased skin temperatures were detected after transdermal application of capsaicin, NVA and SNA ointment bases. The trend of the skin temperature profiles was consistent with that of skin erythema test by laser Doppler flowmetry suggesting that increased skin temperatures may reflect the degree of vasodilation produced by irritation in the treated skin area. In the study of the skin erythema test using various concentration levels of capsaicin and NVA, the various doses from hydrophilic ointment did not markedly influence the pungent and irritant skin reactions after transdermal application.     

Proposal of limit concentrations for skin irritation within the context of a new EEC directive on the classification and labeling of preparations

In this study, solvents belonging to different chemical families were tested for their irritating properties to the skin. The irritating potential of a chemical is expressed as its concentration in a nonirritant diluent beyond which irritation of the skin may be expected in the sense of EEC Directive 79/831/EEC. The substances were applied onto the shaved skin of rabbits by means of a modified Finn chamber for 4 hr. Afterward the exposure chamber was removed and the skin cleaned. Reading of erythema and edema was performed according to the scale of Draize at 1, 24, 48, and 72 hr after the removal of the patch. On the basis of the readings obtained the different dilutions of the organic solvents tested were classified as irritant or not according to the interpretation rules laid down in EEC Directive 83/467/EEC. On the basis of the structure-activity relationships found within each chemical family the irritation potential of the other members of the family could be derived via interpolation.     

Dual Characteristics of Skin Care Creams Evaluated by Two In-Vivo Human Experimental Models

The use of skin care creams is a well documented protection measure to reduce the risk of barrier damage and contact dermatitis from exogenous contact with skin irritants. Before choosing a skin care cream two aspects should be considered: a) Is the product able to reduce irritant reactions caused by the irritant, and b) is the product well tolerated, also on damaged skin. Both aspects can be evaluated by experimental models in human volunteers. We used two standard experimental designs to compare six commercially available skin care products: a) the chamber scarification test, designed to assess the irritancy potential, and b) the repeated short-time occlusive irritation test (ROIT), developed to evaluate the efficacy of skin care creams. The results showed that a high score in the chamber scarification test for skin irritation was not necessarily correlated to the products' ability to impede sodium lauryl sulfate (SLS)-induced irritant skin reactions. Three products were shown to both have a low irritancy potential and be capable of reducing skin barrier damage induced by SLS, and one product had both an irritant potential on scarified skin and also a modest capability to reduce skin irritation induced by SLS. The use of both test methods, chamber scarification and ROIT, gives valuable information on skin compatibility and efficacy of skin care creams. The clinical relevance of the test results can only be determined by comparing products with high and low scores in both tests in controlled clinical experiments with subjects at risk of developing irritant contact dermatitis.     

The usefulness of toxicogenomics for predicting acute skin irritation on in vitro reconstructed human epidermis

In vitro models aiming at replacing the traditional animal test for determining the skin irritation potential of a test substance have been developed, evaluated in prevalidation studies and recently validated by the European Center for the Validation of Alternative Methods (ECVAM). To investigate the usefulness of toxicogenomic technologies to identify novel mechanistic endpoints for skin irritation responses, the present work challenged the human reconstituted epidermis model validated by ECVAM with four irritant chemicals and four non-classified chemicals tested at subcytotoxic concentrations. Using a specifically designed low-density DNA array, about 50 genes out of 240 were found to be significantly and differentially expressed between tissues exposed to irritant and non-irritant chemicals for at least one test chemical when compared to the seven others. These genes are involved in cell signalling, stress response, cell cycle, protein metabolism and cell structure. Among them, 16 are expressed in the same way whatever the irritant compound applied. The differential gene expressions might represent new or additional endpoints useful for the mechanistic understanding and perhaps also the hazard assessment of the skin irritation potential of chemicals and products.     

Non-occlusive topical exposure of human skin in vitro as model for cytotoxicity testing of irritant compounds

Testing of irritant compounds has traditionally been performed on animals and human volunteers. Animal testing should always be restricted and for skin irritancy mice and rabbits hold poor predictive value for irritant potential in humans. Irritant testing on human volunteers is restricted by the duration subjects can be exposed, and by the subjectivity of interpreting the visual signs of skin irritation. We propose an irritant testing system using viable human full thickness skin with the loss of cell viability in the exposed skin area as end point measurement. Skin was exposed to sodium dodecyl sulfate (SDS) at 20% concentration by non-occluded topical exposure to establish a positive control response and subsequent test compounds were statistically compared with the 20% SDS response. Cell viability and metabolism were measured with 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The model presents correlation between increased concentration of SDS and decreased viability of cells in the exposed skin area (R²?=?0.76). We propose the model to be used for cytotoxicity testing of irritant compounds. With fully intact barrier function, the model comprises all cells present in the skin with quantifiable end point measurement.     

长春西汀微乳的优化及其理化性质的考察

目的选择适宜比例的油相、表面活性剂、助表面活性剂和水相制备长春西汀微乳制剂以增加药物的溶解度和经皮渗透量，优化处方，并对其理化性质和刺激性进行研究。方法绘制伪三元相图，确定各相的比例，以经皮稳态渗透流量为指标，利用单纯形网格法优化处方，并考察优化微乳的pH、粘度、电导率、折光率、粒径分布等理化性质。采用MTT法考察微乳制剂对人体皮肤细胞系模型Hacat细胞的毒性。结果O/W微乳在相图中的区域随着表面活性剂和助表面活性剂比例的增加而增加；单纯形网格优化法预测的指标值与实测值相近，所得的优化微乳性质稳定，对Hacat细胞无刺激性，与阴性组无显著性差异。结论长春西汀微乳制剂中药物的溶解度极大提高，经皮稳态渗透流量显著增大，安全稳定，可作为经皮给药的新型载体。     

Design and evaluation of a bioadhesive film for transdermal delivery of propranolol hydrochloride

The objective of the study was to develop a suitable trans-dermal delivery system for propranolol hydrochloride (PPL) via employing chitosan as a film former. Drug concentration uniformity, thickness, moisture uptake capacity and skin bioadhesion of the films were characterized. The effects of chitosan and PPL concentration and different penetration enhancers on the release and permeation profiles from the films were investigated. Skin irritation of the candidate film was evaluated. Chitosan film (PPL 2 mg cm(-2), chitosan 2%, m/m, cineol 10%, m/m) was found nonirritant and achieved 88.2% release after 8 hours in phosphate buffer. Significant high (p < 0.001) permeation of PPL through rat skin was obtained using this film compared to the film without enhancer (about 8 times enhancement factor), making it a promising trans-dermal delivery system for PPL.     

Toxicological studies on sophorolipid derivatives. (I). Acute toxicity, eye irritation, primary skin irritation, skin sensitization, phototoxicity, photosensitization, mutagenicity of polyoxypropylene (12) [(2'-0-beta-D-glucopyranosyl-beta-D-glucopyranosyl)oxy-] fatty acid ester-

Acute toxicity, eye irritation, primary skin irritation, skin sensitization, phototoxicity, photosensitization and mutagenicity of sophorolipid derivatives were studied in rats, mice, rabbits, guinea pigs and Salmonella typhimurium strains. The acute oral toxicity of sophorolipid (SL) which Torulopsis bombicola produces, and its derivatives (PSL, Ethyl-SL and Oleyl-SL) were shown to be very low. The LD50 values of PSL ranged from 10 g/kg to 16 g/kg on oral administration in rats and mice, and from 5.8 g/kg to 6.6 g/kg on subcutaneous administration in mice. The oral LD50 values of Ethyl-SL and Oleyl-SL were estimated to be greater than 15 g/kg and that of SL was 12.5 g/kg. In eye irritation study, PSL failed to produce any reactions at 50% concentration even when the rabbit eye was not subsequently washed. SL, Ethyl-SL, Oleyl-SL and Tween 20 were "no irritant" or "slight irritant" to the rabbit eye at 20% concentration. PSL showed no irritancy to both the intact and abraded guinea pig skin at 50% concentration. And in other examinations, it was also indicated that PSL had no potentials of skin sensitization, phototoxicity and photosensitization in guinea pigs and had no potentials of mutagenicity in Salmonella typhimurium TA98 and TA100.     

Some Naturrally Occurring Skin Irritants

Abstract: Thirteen esters were isolated from the fresh latex of four species of the genus Euphorbia. Structures were elucidated by infra-red, nuclear magnetic resonance and mass-spectroscopy, together with circular dichroism spectroscopy, of the esters and their derivatives or hydrolysis products. Eight of these compounds were new esters of 12-deoxy-phorbol. All the isolated esters produced inflammation of the skin and their relative potencies were assessed by the mice ear test for irritant effects. These compounds were of two types. The first group were diesters with an acetate moiety at carbon 20 and a long chain fatty acid at carbon 13; the second group were mono-esters with a free C-20 hydroxyl group. The mono-esters were more potent than the diesters and their irritant effects were longer lasting. Within both groups of irritants an increase in the chain length of the C-13 acid produced an increase in the irritation of the esters. It was also observed that unsaturation in the side chain increased the potency.     

Harmonization of thresholds for primary skin irritation from results of human repeated insult patch tests and laboratory animal skin irritation tests

Classification of a chemical or chemical product as a primary skin irritant using laboratory animal tests has been defined rigorously and codified in Consumer Products Safety Commission (CPSC) regulations. However, no regulatory agency, including the CPSC, has defined a primary skin irritant threshold for human repeat insult patch tests (RIPTs) that are typically conducted on products, such as cosmetics, anticipated to come into direct contact with humans. Further more, the protocols for animal and human tests are significantly different, as are the schemes for grading responses. Consequently, comparing the results of one type of test with those from the other type has proved to be difficult. In this short communication, we propose a procedure to harmonize the results from these two types of skin irritation tests and suggest that a score of "5" in animal tests, considering 24-h results on unabraded skin, is equivalent to a score of "3" in human RIPTs.     

The suitability of reconstructed human epidermis models for medical device irritation assessment: A comparison of In Vitro and In Vivo testing results

The ISO 10993 standards on biocompatibility assessment of medical devices discourage the use of animal tests when reliable and validated in vitro methods are available. A round robin validation study of in vitro reconstructed human epidermis (RhE) assays was performed as potential replacements for rabbit skin irritation testing. The RhE assays were able to accurately identify strong irritants in dilute medical device extracts. However, there was some uncertainty about whether RhE tissues accurately predicted the results of the rabbit skin patch or intracutaneous irritation test. To address that question, this paper presents in vivo data from the round robin and subsequent follow-up studies. The follow-up studies included simultaneous in vitro RhE model and in vivo testing of round robin polymer samples and the results of dual in vitro/in vivo testing of currently marketed medical device components/materials. Our results show for the first time that for both pure chemicals and medical device extracts the intracutaneous rabbit test is more sensitive to detect irritant activity than the rabbit skin patch test. The studies showed that the RhE models produced results that were essentially equivalent to those from the intracutaneous rabbit skin irritation test. Therefore, it is concluded that RhE in vitro models are acceptable replacements for the in vivo rabbit intracutaneous irritation test for evaluating the irritant potential of medical devices.     

Assessment of contact allergens by dissociation of irritant and sensitizing properties.

The human organotypic skin explant culture (hOSEC) model is a promising alternative in vitro model for screening contact allergens. In this model, the chemical-induced migration of Langerhans cells (LCs) out of the epidermis, evaluated after a 24-h exposure period, is used as a measure of sensitizer potential. As skin irritants can also induce LC migration it is essential that concentrations of test chemicals are used that are not even weakly irritant. Using the hOSEC irritation model chemicals are classified as weak irritants if they are toxic after a 48-h exposure period. Toxicity is determined by methyl green-pyronine (MGP) staining of hOSEC. We studied three frequently used non-sensitizing skin irritants and six potent or frequent human sensitizers in a dose-response. A complete discrimination between non-sensitizers and contact sensitizers was obtained for the chemicals tested when the concentrations used were lower than the weak irritant concentrations. Frequency of positive allergen reactions in patch test of human populations correlated with the difference between weak irritant concentrations and the lowest concentration inducing significant LC migration. Sensitizer potency correlated with chemical irritancy as determined by keratinocyte death. For the compounds tested, the hOSEC model predicted allergenicity in humans better than the guinea pig maximization test and the mouse local lymph node assay.     

Relationship between eye and skin irritation in rabbits using a series of textile fiber finishes.

A series of 76 fiber finishes, typically composed of blends of lubricants, emulsifiers, antistatic agents and fatty acid soaps, were tested in rabbits to determine both the eye and the skin irritation potential. Each finish was classified as being either non-, slightly, mildly, moderately or severely irritating to the target tissue during a 48-h post-treatment period. Seven (9.2%) of the finishes tested were severely irritating to both the skin and the eye; two (2.6%) were determined to be non-irritating to both tissues. While occasionally finishes produced equal degrees of damage resulting in similar irritancy classifications, seven (9.2%) finishes were found to be severely irritating to the skin without producing any irritation in the eye. Conversely, one finish was found to be a severe eye irritant without producing any skin irritation. The suggested use of the skin irritation data to predict the ocular reaction needs to be carefully examined, particularly with materials such as these fiber finishes. The prediction that a severe skin irritant is also a severe eye irritant was demonstrated to be in error with 8 of 75 (10.5%) of the finishes studied. Further, there is little predictive association between the skin and eye irritation for these compounds.     

Use of human skin equivalent Apligraf for in vitro assessment of cumulative skin irritation potential of topical products

The main goal of the present study was to investigate the response of the human skin equivalent Apligraf in vitro to the application of irritant substances and its predictivity as a screening tool for cumulative skin irritant potential in humans. Vaseline, calcipotriol, trans-retinoic acid, and sodium lauryl sulfate were applied to Apligraf in vitro for 24 h. Cell viability (lactate dehydrogenase leakage), release and mRNA expression of the proinflammatory cytokines IL-1alpha and IL-8, and morphological changes were assessed. The same products were applied to 30 healthy volunteers in a double-blind, randomized, vehicle-controlled within-subject study. The skin reactions after repeated 24-h applications over 3 weeks under Finn chamber patches were monitored by visual scoring and biophysical methods (trans-epidermal water loss, chromametry, and blood flow). Sodium lauryl sulfate was cytotoxic to Apligraf, and increased the release and expression of cytokines at low (0.2%, 0. 4%), but not at high (0.8%, 1%) concentrations. It induced severe irritancy in vivo. Trans-retinoic acid increased the expression and release of cytokines with no detectable cytotoxicity and showed moderate irritancy in humans. Although calcipotriol did neither affect cell viability nor the production of cytokines, it induced morphological signs of irritation and was mildly irritant for healthy volunteers. Vaseline was innocuous in vivo and induced no changes in Apligraf. In conclusion, the cumulative skin irritation potential of the tested products could be predicted with Apligraf in a sensitive and specific manner, by monitoring cytotoxicity, proinflammatory cytokines, and morphological changes.     

Percutaneous absorption in diseased skin: an overview

The stratum corneum's (SC) functions include protection from external hazardous environments, prevention of water loss and regulation of body temperature. While intact skin absorption studies are abundant, studies on compromised skin permeability are less common, although products are often used to treat affected skin. We reviewed literature on percutaneous absorption through abnormal skin models. Tape stripping is used to disrupt water barrier function. Studies demonstrated that physicochemical properties influence the stripping effect: water‐soluble drugs are more affected. Abrasion did not affect absorption as much. Freezing is commonly used to preserve skin. It does not seem to modify water absorption, but still increases the penetration of compounds. Comparatively, heating the skin consistently increased percutaneous absorption. Removing SC lipids may increase percutaneous absorption of drugs. Many organic solvents are employed to delipidize. Delipidization with chloroform–methanol increased hydrophilic compound permeability, but not lipophilic. Acetone pre‐treatment enhanced hydrophilic compound penetration. More data is needed to determine influence on highly lipophilic compound penetration. Sodium lauryl sulfate (SLS) induces irritant dermatitis and is frequently used as a model. Studies revealed that SLS increases hydrophilic compound absorption, but not lipophilic. However, skin irritation with other chemicals increases lipophilic penetration as much as hydrophilic. Animal studies show that UV exposure increases percutaneous absorption whereas human studies do not. Human studies show increased penetration in psoriatic and atopic dermatitis skin. The data summarized here begin to characterize flux alteration associated with damaged skin. Understanding the degree of alteration requires interpretation of involved conditions and the enlarging of our database to a more complete physicochemical spectrum. Copyright © 2012 John Wiley & Sons, Ltd.     

Dermal irritation assessment of three benzene sulfonate compounds

Three benzene sulfonate compounds, benzene sulfonate, benzene meta-disulfonate, and para-phenol sulfonate, were reported to be present in groundwater sampled from residential wells near a former disposal site. Concentrations ranged from < 0.005 mg/L to 474 mg/L. Acute dermal irritation studies were performed on rabbits for each of the three sulfonate compounds to determine if they had the potential to cause irritation to the skin of persons using this groundwater for bathing, showering, or other uses where skin would be exposed. The studies were performed by Toxikon Corporation (Bedford, MA) in accordance with the United States Environmental Protection Agency (USEPA)'s 1998 Health Effects Test Guidelines. At the highest concentration tested (5000 mg/L), all three sulfonate compounds were considered to be slight irritants, producing very slight to mild erythema (Draize Score 1). In all cases, the reactions were reversible. At 2000 mg/L, benzene meta-disulfonate and para-phenol sulfonate caused no irritation and were considered not to be irritants. At 2000 mg/L, only benzene sulfonate was considered to be a slight irritant, producing a mild erythema that was completely reversible within 24 hours. Benzene sulfonate was not considered an irritant at 1000 mg/L or at 500 mg/L. It is important to note that all three sulfonate compounds produced only a slight irritation at the highest concentration tested. None of the compounds produced a moderate to severe irritation response (i.e., severe erythema, edema). Furthermore, any irritation response observed at the highest concentrations tested was reversible within 72 hours. The only irritation response observed at the second highest dose was also reversible within 24 hours.     

Assessing the dermal compatibility of a new female incontinence product line

Context: We have developed a line of products designed to better meet the overall needs of women suffering from urinary incontinence. The products are more discrete and contain a unique odor neutralizing technology (ONT).

Objective: This paper describes the overall skin compatibility program for this product line in which the new products were compared to negative controls and/or commercially marketed reference products with an established history of safe use.

Materials and methods: Test products consisted of several product forms (light pads/pantiliners, moderate pads, briefs and taped diapers) with ONT and having various degrees of protection. Studies were conducted using standard protocols for 4-day and 21-day cumulative irritation, the Human Repeat Insult Patch Test (HRIPT), and the Behind-the-Knee (BTK) test for mechanical and chemical irritation. In one 4-day irritation study and one HRIPT, test subjects consisted of individuals with self-assessed sensitive skin. In addition, one 4-day study was conducted using normal skin sites, and sites compromised by tape stripping. Nonirritant controls were physiologic saline and/or current, commercially marketed incontinence products. All responses were evaluated by visual scoring of erythema. In addition, in the BTK, transepidermal water loss (TEWL) and adverse sensory effects collected from panelists’ daily diaries were also evaluated.

Results and discussion: Two 4-day cumulative irritation studies and one 21-day study demonstrated that a wide range of product forms (liners, light and moderate pads, briefs and adult diapers) produced skin reactions similar to the nonirritant controls. The 4-day study conducted using sensitive skin subjects showed good skin compatibility, and the test products were comparable to the nonirritant controls. In the 4-day study with both normal and compromised skin sites, test products produced mean erythema scores similar to the nonirritant controls. Three HRIPT separate studies confirm that the products do not induce contact sensitization, including one study conducted on individuals with self-assessed sensitive skin. In the BTK, test and control products produced similar irritation, as assessed by erythema, TEWL and sensory effects.

Conclusion: The results from the patch tests and mechanical irritation test demonstrate good skin compatibility of the new line of products with the unique ONT. In addition, the forms of the product (i.e. liner, pad or brief), were equally compatible with skin.     

Dermo-epidermal organotypic cultures for in vitro evaluation of skin irritation and corrosion

In recent years, in-vitro skin models for chemical hazard identification have been developed. Most of them consist only of human keratinocytes, neglecting the contribution of other skin constituents. Cultures containing the dermal and epidermal component provide an attractive system to investigate, in a more realistic model, toxicological responses, which represents a distinct advantage over keratinocytes-based models that do not mimic faithfully the in vivo environment.This study aimed to validate dermo-epidermal organotypic cultures (ORGs) as a platform to perform irritation and corrosion tests. Skin models were constructed by seeding keratinocytes on fibroblast-containing fibrin gels. After 21 days, the ORGs were evaluated histologically, and the irritant and corrosion potential was determined by means of viability measurements (MTT assay) and cytokine release, according to 431 and 439 OECD tests guidelines.Skin models showed similar histological characteristics to native skin and were able to classify different substances with high accuracy, showing their applicability to skin irritation and corrosion tests. Although cytokines release seems to be chemical-dependent, a tendency was observed, leading to the improvement of the prediction capacity. Nevertheless, further studies should be done to reduce variability in order to increase prediction capacity.     

Toxicity studies of microbial insecticide Bacillus thuringiensis var. kenyae in rats,rabbits, and fish

Bacillus thuringiensis var. kenyae (B.t.k.) is a microbial insecticide effective against lepidopteran pest species. Acute oral toxicity in rats and acute dermal toxicity, ocular irritation, skin irritation in rabbits were studied for the wettable powder formulation of B.t.k. In addition, toxicity of the wettable powder formulation was also studied in fresh water fish (Gambussia affinis). The results of these studies indicate that this wettable powder formulation of B.t.k. is nontoxic and nonirritant to rats, rabbits, and fish.