Typical clinical “in use” conditions for topical semisolids involve their application as a thin film, often with rubbing that can induce metamorphic stress. Yet, product quality and performance tests often characterize the manufactured product, and may not consider product metamorphosis (e.g., shear history) during dispensing and administration. This work sought to elucidate how such metamorphosis might alter product quality and performance. We evaluated the effect of “in use” stresses on drug crystal metamorphosis in acyclovir creams by optical microscopy. The amount of dissolved acyclovir was determined by separation of the cream base by ultra-centrifugation and quantification by HPLC. IVPT was undertaken on Zovirax® US and Aciclostad® comparing static and “in use” application of a finite dose. A mechanistic IVPT study was also conducted to understand the influence of acyclovir particle size reduction by “in use” rubbing on skin permeation. Reduction in acyclovir particle size was seen after “in use” rubbing with increases in the amount of dissolved acyclovir after rubbing (30 and 60 s) compared to static for both products. “In use” application resulted in significantly higher acyclovir permeation from both products. The mechanistic IVPT study proved the role of product metamorphosis. These results highlight the role of metamorphosis of product microstructure and its influence on performance.

The objective of this study was to investigate whether different dispensing processes can alter the physicochemical and structural (Q3) attributes of a topical cream product, and potentially alter its performance. Acyclovir cream, 5

The presence of esterase enzymes in human skin and their role in drug metabolism has been reported, but their distribution in the various skin layers and the relative contributions of those layers to metabolism is poorly defined. To gain further insight into esterase distribution, we performed in vitro skin permeation of a commercial 28.3% methyl salicylate (MeSA) cream (Metsal™) in Franz diffusion cells, using a range of human skin membranes, all from the same donor. The membranes were viable epidermis separated by a dispase II enzymatic method, heat separated epidermis, dermatomed skin, and dermis separated by a dispase II enzymatic method. Methyl salicylate and its metabolite, salicylic acid (SA), were measured by high-performance liquid chromatography. Alpha naphthyl acetate and Hematoxylin and Eosin staining provided qualitative estimations of esterase distribution in these membranes. The permeation of methyl salicylate after 24 h was similar across all membranes. Salicylic acid formation and permeation were found to be similar in dermatomed skin and dermis, suggesting dermal esterase activity. These results were supported by the staining studies, which showed strong esterase activity in the dermal–epidermal junction region of the dermis. In contrast with high staining of esterase activity in the stratum corneum and viable epidermis, minimal stained and functional esterase activity was found in heat-separated and dispase II-prepared epidermal membranes. The results are consistent with dispase II digesting hemidesmosomes, penetrating the epidermis, and affecting epidermal esterases but not those in the dermis. Accordingly, whilst the resulting dispase II-generated dermal membranes may be used for in vitro permeation tests (IVPT) involving esterase-based metabolic studies, the dispase II-generated epidermal membranes are not suitable for this purpose.

The permeation of hydrophilic molecules through the skin is still a challenge due to the barrier posed by stratum corneum, the outermost layer of the skin. Liposomes have frequently been used as carriers for different types of drugs and may also function as permeation enhancers. Propylene glycol has also been used as an edge activator in liposomes to increase the permeation. The aim of this work was to prepare liposomes containing an edge activator and loaded with caffeine to evaluate the potential of caffeine reaching the deeper layers in the skin.

This chapter discusses how the innate and adaptive immune systems provide a comprehensive structural, chemical, and immunological barrier to external agents and microbiological pathogens. It presents the issue of irritant and allergic contact dermatitis that can occur with all forms of cosmetics applied to the skin. The immune system in the skin can also be the source for innovation and therapeutic targets for common cosmetic considerations such as hyperpigmentation and photoprotection. It is anticipated that the field of cosmetic science will continue to learn from new advances in skin immunology to target or protect against erythema, dyschromia and photoaging. The different classes of skin reactions are allergic contact dermatitis. Allergic contact dermatitis is an adaptive immune response to allergen exposure, often to chemicals as an initial step of sensitization, followed by a response elicited by re-exposure to the same allergen. Irritant contact dermatitis is the result of activation of the innate immune system and its response to the penetrated chemical.

BACKGROUND:Pig skin is a widely acknowledged surrogate for human skin for in vitro/ex vivo skin penetration studies with application for small molecules and nanosystems. We have investigated the influence of biological factors such as age and anatomical site on the penetration and distribution of nanoparticles (2.1 nm hydrophilic CdTe/CdS quantum dots: QDs) in adult pig skin (APS), weanling pig skin (WPS) and newborn pig skin (NBPS) at two different anatomical sites (ear and abdomen).METHODS:QDs in saline were applied to 1 × 1 cm2 skin (62.5 pmol/cm2) with 2-min finger rubbing using a standardized protocol. After 6- or 24-h incubation on Franz diffusion cells, tape stripping (×10) followed by manual follicular casting was conducted. Cadmium in QDs was quantified using inductively coupled plasma mass spectrometry for all samples. The presence of QDs in similarly treated skin samples was also captured using multiphoton tomography.RESULTS:QDs were mainly localized in hair follicles after 6 and 24 h of exposure with no cadmium detected in the Franz cell receptor compartment regardless of pig age or anatomical site. The amount of QDs deposited in the follicles was similar at 6 h but higher on APS and WPS ears compared to NBPS ears at 24 h. This is associated with the high follicle density and small follicle diameter of the NBPS compared to the smaller density of much larger follicles on the APS. NBPS showed consistent QD distribution for ear and abdomen up to 24 h.CONCLUSIONS:There is minimal penetration of QDs through pig skin. Density and diameter of follicles in association with age of pigs and application site influenced the amount of QDs deposited in follicles. The structure of the stratum corneum, follicle density and diameter of NBPS are similar to human skin suggesting that NBPS is an appropriate model for human skin in the evaluation of topical applications of a range of chemicals including nanosystems.

The purpose of this study was to evaluate the safety of Kalanchoe brasiliensis extract, followed by the development of an oil in water emulsion containing the K. brasiliensis leaves extract and evaluating its clinical moisturizing efficacy. The formulations containing sodium acrylates/ Beheneth-25 methacrylate Crosspolymer (and) hydrogenated polydecene (and) lauryl glucoside and 0.5% of extract were prepared. The extract was considered as non-irritating through skin irritant tests. The stability testing was carried out in different conditions for 90 days. The skin hydration was measured by capacitance measurement and transepidermal water loss using biophysical techniques. The results indicate that the formulation containing 0.5% of extract increased the hydration of the stratum corneum up to 5 h after application on the forearm. The transepidermal water loss was reduced when compared to the untreated area and placebo area. Therefore, we can conclude that the increased skin hydration and protection of barrier function can be attributed to the K. brasiliensis extract. This research presents a new raw material from the Brazilian Caatinga biome and shows its possible application in the development of cosmetic products.

The mathematical model describing drug flux through microporated skin was previously developed. Based on this model, two mathematical equations can be used to predict the microporatio-enhanced transdermal drug flux: the complex primal equation containing a variety of experimentally-determined variables, and the simplified straightforward equation. In this study, experimental transdermal fluxes of three corticosteroids through split-thickness human skin treated with a microneedle roller were measured, and the values of fluxes compared with those predicted using both the more complex and simplified equations. According to the results of the study, both equations demonstrated high accuracy in the prediction of the fluxes of corticosteroids. The simplified equation was validated and confirmed as robust using regression analysis of literature data. Further, its capability and ease of use was exemplified by predicting the flux of methotrexate through the skin microporated with laser and comparing with published experimental data.

The assessment of percutaneous permeation of molecules is a key step in the evaluation of dermal or transdermal delivery systems. If the drugs are intended for delivery to humans, the most appropriate setting in which to do the assessment is the in vivo human. However, this may not be possible for ethical, practical, or economic reasons, particularly in the early phases of development. It is thus necessary to find alternative methods using accessible and reproducible surrogates for in vivo human skin. A range of models has been developed, including ex vivo human skin, usually obtained from cadavers or plastic surgery patients, ex vivo animal skin, and artificial or reconstructed skin models. Increasingly, largely driven by regulatory authorities and industry, there is a focus on developing standardized techniques and protocols. With this comes the need to demonstrate that the surrogate models produce results that correlate with those from in vivo human studies and that they can be used to show bioequivalence of different topical products. This review discusses the alternative skin models that have been developed as surrogates for normal and diseased skin and examines the concepts of using model systems for in vitro-in vivo correlation and the demonstration of bioequivalence.

Apocynin is a major active constituent of Picrorhiza kurroa that exhibits potent anti-inflammatory activity by inhibiting superoxide-generating NADPH oxidase enzyme. To elucidate detailed pharmacokinetic profile of apocynin, high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed in rat and human plasma. To the best of our knowledge, this is the first method for complete validation of apocynin in biological matrix using LC-MS/MS. Apocynin was rapidly absorbed after oral administration at 50mg/kg in rats and peak plasma level achieved within 5min. Moreover, plasma levels were observed up to 48h. The bioavailibity of apocynin was found to be 8.3%. In vitro plasma protein binding was found to be 83.41-86.07% and 71.39-73.34% in rat and human plasma, respectively. Apocynin was found stable in gastric (pH 1.2), intestinal (pH 6.8) and physiological (pH 7.4) fluids including microsomal (rat and human) stability studies. Further, apocynin did not convert to its dimeric form diapocynin in any of these studies. The data presented here provide crucial information about apocynin to support its pharmacological efficacy and further development as a potential anti-inflammatory drug candidate.

Antileishmanial activities of a library of synthetic chalcone analogues have been examined. Among them, five compounds (11, 14, 16, 17, 22, and 24) exhibited better activity than the marketed drug miltefosine in in vitro studies against the intracellular amastigotes form of Leishmania donovani. Three promising compounds, 16, 17, and 22, were tested in a L. donovani/hamster model. Oral administration of chalcone 16, at a concentration of 100 mg/kg of body weight per day for 5 consecutive days, resulted in >84% parasite inhibition at day 7 post-treatment and it retained the activity until day 28. The molecular and immunological studies revealed that compound 16 has a dual nature to act as a direct parasite killing agent and as a host immunostimulant. Pharmacokinetics and serum albumin binding studies also suggest that compound 16 has the potential to be a candidate for the treatment of the nonhealing form of leishmaniasis.

Natamycin is the only approved medication for the treatment of mycotic keratitis. Current dosage regimen include one drop of natamycin suspension (5% w/v) instilled in the conjunctival sac at hourly or two hourly intervals for several days which has poor patient compliance. The purpose of the present study was to design a corneal targeted nanoformulation in order to reduce dose and dosing frequency of natamycin and evaluate its pharmacokinetic/pharmacodynamic indices in comparison with clinical marketed preparation. The nanoparticles prepared by nanoprecipitation method were in nanometer size range with high entrapment efficiency and positive surface charge. In-vitro release studies indicated prolonged release of natamycin up to 8h. In-vitro antifungal activity was comparable with marketed preparation. The performance of nanoformulations was evaluated in rabbit eyes. The concentration of natamycin in tear fluid was determined by using LC–MS/MS. The pharmacokinetic parameters such as area under the curve, t½ and mean residence time were significantly higher and clearance was significantly lower for nanoformulations with that of marketed preparation. The optimized dosing schedule to maintain natamycin concentration above tenfold of MIC90 was one instillation in every 5h. Moreover, 1/5th dose reduction of nanoformulation was also effective.