Topical glycerol monooleate/propylene glycol formulations enhance 5-aminolevulinic acid in vitro skin delivery and in vivo protophorphyrin IX accumulation in hairless mouse skin

Photodynamic therapy (PDT), a potential therapy for cancer treatment, utilizes exogenously applied or endogenously formed photosensitizers, further activated by light in an appropriate wavelength and dose to induce cell death through free radical formation. 5-Aminolevulinic acid (5-ALA) is a pro-drug which can be converted to the effective photosensitizer, protoporphyrin IX (PpIX). However, the use of 5-ALA in PDT is limited by the low penetration capacity of this highly hydrophilic molecule into appropriate skin layers. In the present study, we propose to increase 5-ALA penetration by using formulations containing glycerol monooleate (GMO), an interesting and useful component of pharmaceutical formulations. Propylene glycol solutions containing different concentrations of GMO significantly increased the in vitro skin permeation/retention of 5-ALA in comparison to control solutions. In vivo studies also showed increased PpIX accumulation in mouse hairless skin, after the use of topical 5-ALA formulations containing GMO in a concentration-dependent manner. The results show that skin 5-ALA penetration and PpIX accumulation, important factors for the success of topical 5-ALA-PDT in skin cancer, are optimized by GMO/propylene glycol formulations.     

<Emphasis Type="Italic">In Vitro</Emphasis> Metabolism of 5-ALA Esters Derivatives in Hairless Mice Skin Homogenate and <Emphasis Type="Italic">in Vivo</Emphasis> PpIX Accumulation Studies

No HeadingPurpose. In topical photodynamic therapy, 5-ALA and its esters are enzymatically converted in the endogenous photosensitizing compounds such as, for example, protoporphyrin IX (PpIX). In order to elucidate in more detail their enzymatic fate, we have determined in vitro the enzymatic degradation of methyl, butyl, hexyl, and octyl-5-ALA ester derivatives in skin homogenate. Furthermore, in vivo porphyrin accumulation was measured in healthy hairless mice skins.Methods. Hairless mouse skins were homogenized in isotonic phosphate buffer pH 7.4. 5-ALA esters were added, and aliquots were colleted for HPLC-fluorimetric determinations of remaining content of 5-ALA esters. Furthermore, oil-in-water emulsions containing esters were topically applied to mice skin for 6 h, and the amount of accumulated PpIX in the treated areas was determined by quantitative extraction and confocal fluorescence microscopy.Results. The enzymatic degradation of esters follows pseudo first-order kinetics. The octyl ester had the largest rate constant for enzymatic degradation, followed by hexyl-, butyl-, and methyl-ALA. The long-chained 5-ALA esters, butyl-, hexyl-, and octyl ester, induced significantly more porphyrins than 5-ALA and 5-ALA methyl ester as shown by confocal microscopy and quantitative extraction studies.Conclusions. 5-ALA derivatives differ widely with respect to their enzymatic degradation. The presence of alkyl chains in 5-ALA esters significantly influences the in vitro enzymatic metabolism and the in vivo PpIX formation in healthy hairless mice skins.     

Desferrioxamine Enhances 5-Aminolaevulinic Acid- Induced Protoporphyrin IX Accumulation and Therapeutic Efficacy for Hypertrophic Scar

Hypertrophic scar is a common problem after skin burns or trauma which brings physical, psychological, and cosmetic problems to patients. Photodynamic therapy with 5-aminolevulinic acid (5-ALA) is a promising therapy for hypertrophic scar. However, clinical applications of 5-ALA are limited because of the low permeability of 5-ALA in the skin stratum corneum and the rapid binding of protoporphyrin IX (PpIX) with iron ions, which lead to insufficient PpIX production in target tissues. Herein, a mixture of 5-ALA and DFO (deferoxamine, a special iron chelator) was applied for the treatment of hypertrophic scar. 5-ALA/DFO could efficiently block the biotransformation of PpIX to heme, thus realizing a significant accumulation of photosensitizer. In addition, injection locally into the lesion was applied, which combined with enhanced photodynamic therapy to destroy hypertrophic scar fibroblasts. In vitro experiments showed that 5-ALA/DFO could increase more ROS generation by increasing the accumulation of PpIX, resulting in the apoptosis of hypertrophic scar fibroblasts. Furthermore, 5-ALA/DFO inhibited the proliferation and migration of hypertrophic scar fibroblasts. In vivo study showed that 5-ALA/DFO could effectively inhibit the formation of proliferative scar. Therefore, 5-ALA/DFO has the potential to enhance the photodynamic therapy of 5-ALA and provides a new treatment strategy for hypertrophic scar.     

Autoradiographic and Scintillation Analysis of 5-Aminolevulinic Acid Permeation Through Epithelialised Tissue: Implications for Topical Photodynamic Therapy of Superficial Gynaecological Neoplasias

Purpose Aminolevulinic acid (5-ALA) diffusion through both keratinised and non-keratinised tissue, used as a model tissue substrates, was evaluated, together with the depth of permeation and the concentration achieved following delivery from bioadhesive patch and proprietary cream formulations. Materials and Methods Moisture-activated, bioadhesive patches loaded with 5-ALA at concentrations of 19.0, 38.0 and 50.0 mg cm⁻² and an o/w cream (20% w/w 5-ALA) were radiolabelled with C14 5-ALA and applied to excised human vaginal tissue and porcine skin. After 1, 2 and 4 h, tissue was sectioned in two orientations and the 5-ALA concentration at specific depths determined using autoradiography and liquid scintillation counting (LSC). Results The stratum corneum was a significant barrier to 5-ALA permeation, with concentrations in tissue dependent on application time and drug loading. 5-ALA was detected at 6 mm using autoradiography after 2 h, with LSC showing phototoxic concentrations at 2.375 mm after 4 h of application. Inclusion of oleic acid and dimethyl sulphoxide in bioadhesive patches increased 5-ALA significantly in neonate porcine tissue, but only for patches cast from blends containing 5% w/w oleic acid. Conclusions The bioadhesive patch described delivered 5-ALA to depths of at least 2.5 mm in tissue types indicative of vulval skin, suggesting that photodynamic therapy of deep vulval intraepithelial neoplasia is feasible using this means of bioadhesive 5-ALA delivery.     

Photodynamic Therapy of Skin Cancers: Sensitizers,Clinical Studies and Future Directives

Photodynamic therapy (PDT) is a new modality of skin cancer treatment. It involves the administration of photosensitizing drugs which, when localized in tumor tissue can produce its destruction by absorbing an adequate dose of light of an appropriate wavelength. A large number of photosensitizing agents have been tested in PDT experiments. Topical application of 5-aminolevulinic acid (5-ALA) followed by light irradiation is the most commonly used method. 5-ALA is a prodrug converted in situ via the heme cycle into protoporphyrin IX, an effective photosensitizer agent. Treatment of nonmelanoma skin cancers by PDT has met with varying degrees of success. In the case of 5-ALA, this therapy's main limitation is the poor penetration of 5-ALA into skin, due to hydrophilic and charge characteristics. However, the efficacy of 5-ALA-PDT may be improved by (a) development of adequate drug delivery systems; (b) use of enhancers of PpIX production and accumulation in target tissue, and (c) modifications of the 5-ALA molecule. Optimal timing, light sources, doses, and number of applications are also important factors for topical 5-ALA therapy and must be well defined. The aim of this review is to highlight recent progress in 5-ALA-PDT of skin cancer, and to present ways holding promise for its improvement.     

Topical gels of etofenamate: in vitro and in vivo evaluation

Abstract

Non-steroid anti-inflammatory drugs (NSAIDs), such as etofenamate, are among the most prescribed drugs used for their analgesic, anti-rheumatic, antipyretic and anti-inflammatory properties. Topical formulations have the main advantage of targeted delivery. However, drugs must overcome the skin due to its role as a physical and chemical barrier against the penetration of chemicals and microorganisms. This barrier must be altered to allow the permeation of drugs at a suitable rate to the desired site of activity. Permeation modulators can intercalate the skin outer layers causing structure disruption, opening an energetically favourable route for the drug to diffuse through. The aim of this work was the development of hydroalcoholic gels containing 5.0% (w/w) of etofenamate for topical administration with anti-inflammatory activity and enhanced drug delivery. The physical and chemical characterization, in vitro release and permeation studies and in vivo anti-inflammatory activity were assessed. The gel with 30% ethanol showed in vivo anti-inflammatory activity with suitable physical chemical and microbiologic characteristics. In vitro release and permeation studies revealed that the different amounts of ethanol used influenced the release profiles of etofenamate. Moreover, it was demonstrated that this formulation is an adequate vehicle for the etofenamate skin permeation.     

Liposomes in topical photodynamic therapy

Introduction: Topical photodynamic therapy (PDT) refers to topical application of a photosensitizer onto the site of skin disease which is followed by illumination and results in death of selected cells. The main problem in topical PDT is insufficient penetration of the photosensitizer into the skin, which limits its use to superficial skin lesions. In order to overcome this problem, recent studies tested liposomes as delivery systems for photosensitizers.

Areas covered: This paper reviews the use of different types of liposomes for encapsulating photosensitizers for topical PDT. Liposomes should enhance the photosensitizers' penetration into the skin, while decreasing its absorption into systemic circulation. Only few photosensitizers have currently been encapsulated in liposomes for topical PDT: 5-aminolevulinic acid (5-ALA), temoporfin (mTHPC) and methylene blue.

Expert opinion: Investigated liposomes enhanced the skin penetration of 5-ALA and mTHPC, reduced their systemic absorption and reduced their cytotoxicity compared with free drugs. Their high tissue penetration should enable the treatment of deep and hyperkeratotic skin lesions, which is the main goal of using liposomes. However, liposomes still do not attract enough attention as drug carriers in topical PDT. In vivo studies of their therapeutic effectiveness are needed in order to obtain enough evidence for their potential clinical use as carriers for photosensitizers in topical PDT.     

Reverse Hexagonal Phase Nanodispersion of Monoolein and Oleic Acid for Topical Delivery of Peptides: in Vitro and in Vivo Skin Penetration of Cyclosporin A

Purpose To obtain and characterize reverse hexagonal phase nanodispersions of monoolein and oleic acid, and to evaluate the ability of such system to improve the skin penetration of a model peptide (cyclosporin A, CysA) without causing skin irritation. Methods The nanodispersion was prepared by mixing monoolein, oleic acid, poloxamer, and water. CysA was added to the lipid mixture to obtain a final concentration of 0.6% (w/w). The nanodispersion was characterized; the skin penetration of CysA was assessed in vitro (using porcine ear skin mounted in a Franz diffusion cell) and in vivo (using hairless mice). Results The obtainment of the hexagonal phase nanodispersion was demonstrated by polarized light microscopy, cryo-TEM and small angle X-ray diffraction. Particle diameter was 181.77 ± 1.08 nm. At 0.6%, CysA did not change the liquid crystalline structure of the particles. The nanodispersion promoted the skin penetration of CysA both in vitro and in vivo. In vitro, the maximal concentrations (after 12 h) of CysA obtained in the stratum corneum (SC) and in the epidermis without stratum corneum (E) + dermis (D) were ∼2 fold higher when CysA was incorporated in the nanodispersion than when it was incorporated in the control formulation (olive oil). In vivo, 1.5- and 2.8-times higher concentrations were achieved in the SC and [E+D], respectively, when the nanodispersion was employed. No histopathological alterations were observed in the skin of animals treated with the nanodispersion. Conclusion These results demonstrate that the hexagonal phase nanodispersion is effective in improving the topical delivery of peptides without causing skin irritation.     

In Vivo and in Vitro Analysis of Skin Penetration Enhancement Based on a Two-Layer Diffusion Model with Polar and Nonpolar Routes in the Stratum Corneum

In vitro and in vivo skin penetration of three drugs with different lipophilicities and the enhancing effects of l-geranylazacycloheptan-2-one (GACH) were studied in rats. In vivo drug absorption profiles obtained by deconvolution of urinary excretion profiles were compared to the corresponding in vitro data obtained with a diffusion experiment. In vivo skin penetration of lipophilic butylparaben was considerably greater than that observed in vitro, while hydrophilic mannitol and acyclovir showed low penetration in both systems without GACH pretreatment. On the other hand, GACH enhanced mannitol and acyclovir penetration, especially in the in vivo system. Analysis of absorption profiles, using a two-layer skin model with polar and nonpolar routes in the stratum corneum, suggested that the diffusion length of a viable layer (viable epidermis and dermis) was shorter in vivo than in vitro and the effective area of the polar route in the stratum corneum was larger in vitro without GACH pretreatment. GACH increased the partitioning of acyclovir into the nonpolar route to the same extent in both systems. In addition, GACH increased the effective area of the polar route in vivo, probably because of enhanced water permeability; however, this effect was smaller in vitro since the stratum corneum was already hydrated even without GACH pretreatment.     

不同透皮促进剂对双氯芬酸钾凝胶体外透皮效果的影响研究

目的:考察氮酮(Azone)、丙二醇(PG)、油酸(OA)3种透皮促进剂一元、二元、三元联合对双氯芬酸钾凝胶的体外促透作用。方法:配制以下13种含不同透皮促进剂的双氯芬酸钾凝胶处方:空白,3%Azone,5%OA,12%PG,6%PG+2.5%OA,12%PG+5%OA,1.5%Azone+2.5%OA,1.5%Azone+6%PG+5%OA,1.5%Azone+12%PG,3%Azone+5%OA,3%Azone+6%PG,3%Azone+6%PG+5%OA,3%Azone+12%PG,以透皮速率J等为指标,采用改良的Franz扩散池,以离体人皮肤为透皮屏障,测定并计算双氯芬酸钾凝胶加入上述不同透皮促进剂处理后药物的透皮性能。结果:与空白组比较,其它各组J值均升高,其中以3%Azone+12%PG组的J值最高,达10.253 0μg.cm-2.h-1。结论:3种透皮促进剂对双氯芬酸钾凝胶均有不同程度促透效果,但以Azone和PG二元联用效果最佳。     

Assessment of the percutaneous penetration of cisplatin: The effect of monoolein and the drug skin penetration pathway

It was intended to examine the in vitro penetration of cisplatin (CIS) through porcine skin in the presence of different concentrations of monoolein (MO) as well as to verify the main barrier for CIS skin penetration. In vitro skin penetration of CIS was studied from propylene glycol (PG) solutions containing 0%, 5%, 10%, and 20% of MO using Franz-type diffusion cell and porcine ear skin. Pretreatment experiments with MO and experiments with skin without stratum corneum (SC) were also carried out. Skin penetration studies of CIS showed that the presence of MO doubled the drug permeation through the intact skin. However, permeation studies through the skin without SC caused only a small enhancement of CIS permeation compared to intact skin. Moreover, pretreatment of skin with MO formulations did not show any significant increase in the flux of the drug. In conclusion, MO did not act as a real penetration enhancer for CIS, but it increased the drug partition to the receptor solution improving CIS transdermal permeation. The absence of improvement in drug permeation by MO pretreatment and by the removal of SC indicates that the SC is not the main barrier for the permeation of the metal coordination compound.     

In Vivo Evaluation of Acyclovir Prodrug Penetration and Metabolism Through Rat Skin Using a Diffusion/Bioconversion Model

Purpose. In order to evaluate the in vivo penetration of prodrugs which undergo metabolism in skin, we analyzed thein vivo penetration profiles of acyclovir prodrugs based on a two-layer skin diffusion model in consideration of metabolic process. Methods. Acyclovir prodrugs (e.g., valerate, isovalerate and pivarate) were used as model prodrugs and the amounts excreted in urine were measured after percutaneous application. In vivo penetration profiles were then estimated by employing a deconvolution method and the penetration of acyclovir prodrugs was analyzed using a diffusion model. Subsequently, diffusion, partitioning and metabolic parameters were compared under in vitro and in vivo conditions. Results. Although total penetration amounts at the end of the experiment were similar for the three prodrugs, the ratio of intact prodrug to total penetration amount differed significantly. Moreover, the excretion and absorption profiles were also very different for each prodrug. Enzymatic hydrolysis rate constants calculated under in vivo conditions were considerably larger than those obtained in the skin homogenate and in vitro penetration experiments. Conclusions. The present skin diffusion/bioconversion model combined with computer analysis enables us to comprehensively account for diffusion, partitioning and metabolism during in vivo percutaneous absorption. Nevertheless, different enzymatic hydrolysis rate constants obtained under bothin vivo and in vitro conditions demonstrate the difficulty of obtaining accurate values for in vivo enzymatic activity from related in vitro experiments.     

Effect of Penetration Enhancers on the Transdermal Delivery of Bupranolol Through Rat Skin

Bupranolol (BPL) is a suitable drug candidate for transdermal drug delivery system development based on its favorable physicochemical and pharmacokinetic properties. The effect of different penetration enhancers on the permeation of BPL across rat skin was studied using side-by-side diffusion cells. 2-pyrrolidone (PY), 1-methyl-2-pyrrolidone (MPY), and propylene glycol (PG) at various concentrations were used as penetration enhancers along with 0.4% w/v aqueous suspension of BPL. Menthol at different concentrations in isopropanol-water (6:4) mixture also was used as an enhancer wherein BPL at 0.4% w/v was completely solubilized. Skin pretreatment studies were carried out with all the above enhancers to understand their role in the penetration enhancement effect. PY and MPY at 5% w/v concentrations increased the permeation of BPL by 3.8- and 2.4-fold, respectively, versus control (p < .01). PG at 10% and 30 w/v concentrations increased the flux of BPL by 2.5- and 5.0-fold, respectively, versus control (p < .001). Menthol at 2% w/v concentration increased the flux of BPL by 3.8-fold (p < .01) and further increase in menthol concentration significantly decreased the flux of BPL. Overall, pyrrolidones and menthol at low concentrations (5% w/v or less) and PG at 30% w/v concentration were effective as penetration enhancers for BPL.     

Site-Specific Drug Delivery to Pilosebaceous Structures Using Polymeric Microspheres

In order to improve the therapeutic index of adapalene, a new drug under development for the treatment of acne, site-specific delivery to the hair follicles using 50:50 poly(DL-lactic-co-glycolic acid) microspheres as particulate carriers was investigated in vitro and in vivo. The percutaneous penetration pathway of the microspheres was shown to be dependent on their mean diameter. Thus, after topical application onto hairless rat or human skin, adapalene-loaded microspheres (5-µm diameter) were specifically targeted to the follicular ducts and did not penetrate via the stratum corneum. The in vitro release of adapalene from the microspheres into artificial sebum at 37°C was controlled and faster than the in vivo sebum excretion in humans. Aiming to reduce either the applied dose of drug or the frequency of administration, different formulations of adapalene-loaded microspheres were evaluated in vivo in the rhino mouse model. A dose-related comedolytic activity of topical formulations of adapalene-loaded microspheres was observed in this model. Furthermore, by applying a site-specific drug delivery system (0.1% adapalene) every other day or by administering a 10-fold less concentrated targeted formulation (0.01%) every day, a pharmacological activity equivalent to a daily application of an aqueous gel containing drug crystals (0.1% adapalene) was observed. Since an aqueous gel containing 10% adapalene-loaded microspheres was not irritating in a rabbit skin irritancy test, this formulation was applied onto forearms of human volunteers. Site-specific drug delivery was further evidenced by follicular biopsy. These results support the view that follicular drug targeting using 5-µm polymeric microspheres may represent a promising therapeutic approach for the treatment of pathologies associated with pilosebaceous units.     

Hexyl Aminolaevulinate Is a More Effective Topical Photosensitiser Precursor than Methyl Aminolaevulinate and 5-Aminolaevulinic Acids When Applied in Equimolar Doses

Aminolaevulinic acid (ALA) is known to poorly penetrate into thick lesions, such as nodular basal cell carcinomas. Short chain ALA esters, possessing increased lipophilicity relative to their hydrophilic parent, have previously been shown to be highly efficient at inducing protoporphyrin IX (PplX) production in cell culture, at equimolar concentrations. In contrast, in vitro skin permeation and in vivo animal studies, which up to now have compared prodrugs on a % w/w basis, have failed to demonstrate such benefits. For the first time, equimolar concentrations of ALA, methyl-ALA (m-ALA) and hexyl-ALA (h-ALA) have been incorporated into an o/w cream preparation. In vitro penetration studies into excised porcine skin revealed that increased levels of h-ALA, compared to ALA and m-ALA were found in the upper skin layers, at all drug loadings studied. Topical application of the formulations to nude murine skin in vivo, revealed that creams containing h-ALA induced significantly higher levels of peak PplX fluorescence (F_max = 289.0) at low concentrations compared to m-ALA (F_max = 159.2) and ALA (F_max = 191.9). Importantly, this study indicates that when compared on an equimolar basis, h-ALA has improved skin penetration, leading to enhanced PpIX production compared to the parent drug and m-ALA. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3486–3498, 2010     

Drug Distribution in Human Skin Using Two Different In Vitro Test Systems: Comparison with In Vivo Data

Purpose. Two in vitro test systems used to study drug penetration into human skin—the Franz diffusion cell (FD-C) and the Saarbruecken penetration model (SB-M)—were evaluated, and the results were compared with data gained under analogous in vivo conditions. Methods. Excised human skin was used in all in vitro experiments. Flufenamic acid dissolved in wool alcohols ointment, was chosen as a model drug, and the preparation was applied using infinite dose conditions. To acquire quantitative information about the drug penetration, the skin was segmented into surface parallel sections at the end of each experiment, first by tape stripping the stratum corneum (SC), and second by cutting the deeper skin layers with a cryomicrotome. The flufenamic acid was extracted from each sample and assayed by high performance liquid chromatography (HPLC). For in vivo experiments, only the tape stripping technique was used. Results. a) Drug penetration into the SC: In both in vitro test systems the total drug amounts detected in the SC were found to increase over the different incubation times. Similar conditions were obtained in vivo, but on a lower level. Using Michaelis-Menten kinetics, the m_max value was calculated for the skin of two donors. The relations of the m_max values for the FD-C and the SB-M closely correspond (1.26 [donor 1] and 1.29 [donor 2]). A direct linear correlation of the drug amount in the SC and the time data were found for in vivo with both in vitro test systems.%b) Drug penetration into the deeper skin layers: The detected drug amounts in the deeper skin layers continuously increased with the incubation time in the SB-M, while in the FD-C, only very small drug amounts were observed after incubation times of 30 and 60 minutes. It was also noticed, that the drug amounts rose steeply at time points 3 and 6 hours. Additional studies showed a remarkable penetration of water into the skin from the basolateral acceptor compartment in the FD-C. This could explain the different drug transport into the deeper skin layers between the two in vitro test systems. Conclusions. Both in vitro models showed comparable results for the drug penetration into the SC and a robust correlation with in vitro data. Different results were obtained for the deeper skin layers. Whether a correlation between in vitro and in vivo data is also possible here has to be investigated by further experiments.     

The effect of sorption promoters on percutaneous permeation of a model zwitterion baclofen

In vitro percutaneous penetration of baclofen, a model zwitterion, in the presence of penetration enhancers was investigated to better characterize a porous polar pathway of diffusion across the stratum corneum. The following sorption promoters were studied: DMSO, urea, propylene glycol (PG), sodium lauryl sulphate (SLS), ethanol 95%, Azone, oleic acid (OA) and OA/PG system. No significant increase of penetration or skin accumulation of baclofen was observed when DMSO, urea, PG, Azone or OA were used. The presence of SLS or OA/PG in the vehicle resulted in high penetration rates and uptake of baclofen but this effect was observable only after 30 h and was accompanied with signs of the barrier damage. Ethanol 95% was the only vehicle which promoted baclofen penetration despite its lower solubility in this solvent which is attributed to new pore formation. Penetration rate and skin accumulation of the zwitterion depend on its solubility in the vehicle.     

Enhancing and sustaining the topical ocular delivery of fluconazole using chitosan solution and poloxamer/chitosan in situ forming gel

Fungal keratitis is a serious disease that can lead to loss of vision. Unfortunately, current therapeutic options often result in poor bioavailability of antifungal agents due to protective mechanisms of the eye. The aim of this work was to evaluate the potential of a chitosan solution as well as an in situ gel-forming system comprised of poloxamer/chitosan as vehicles for enhanced corneal permeation and sustained release of fluconazole (FLU). For this, in vitro release and ex vivo corneal permeation experiments were carried out as a function of chitosan concentration from formulation containing the chitosan alone and combined with the thermosensitive polymer, poloxamer. Microdialysis was employed in a rabbit model to evaluate the in vivo performance of the formulations. The in vitro release studies showed the sustained release of FLU from the poloxamer/chitosan formulation. Ex vivo permeation studies across porcine cornea demonstrated that the formulations studied have a permeation-enhancing effect that is independent of chitosan concentration in the range from 0.5 to 1.5% w/w. The chitosan solutions alone showed the greatest ex vivo drug permeation; however, the poloxamer/chitosan formulation presented similar in vivo performance than the chitosan solution at 1.0%; both formulations showed sustained release and about 3.5-fold greater total amount of FLU permeated when compared to simple aqueous solutions of the drug. In conclusion, it was demonstrated that both the in situ gelling formulation evaluated and the chitosan solution are viable alternatives to enhance ocular bioavailability in the treatment of fungal keratitis.     

Effect of microemulsion in topical sertaconazole hydrogel: in vitro and in vivo study

Purpose: A topical microemulsion (ME)-based hydrogel was developed to enhance permeation of an antifungal drug, sertaconazole (STZL) for effective eradication of cutaneous fungal infection.

Methods: Pseudo-ternary phase diagrams were used to determine the existence of MEs region. ME formulations were prepared with oleic acid, Tween 80, propylene glycol (PG) and water. Carbopol 940 (0.75% w/w) was used for preparation of hydrogel of STZL microemulsion (HSM) and characterized. The in vitro and in vivo evaluation of prepared HSM and commercial cream of STZL were compared.

Results: The viscosity, average droplet size and pH of HSM were 154.23?±?0.54 to 162.52?±?0.21?Pas, 42.3–91.7?nm and 6.9–7.2?, respectively. Permeation rate of STZL from optimized formulation (HSM-4), composed with oleic acid (8.75 % w/w), Tween 80 (33.35% w/w), PG (33.35% w/w) and water (24.55% w/w) was observed higher in compare with other HSMs and commercial cream. HSM-4 was stable, three times higher drug retention capacity in skin than commercial cream and did not caused any erythema or edema based on skin sensitivity study on rabbit. The average zone of inhibition of HSM-4 (23.54?±?0.72?mm) was higher in compare with commercial cream (16.53?±?0.63?mm) against Candida albicans.

Conclusion: The results of study showed that ME played a major role in permeation enhancing and skin retention effect of HSM and the concentration of STZL used for cutaneous fungal infection could be decreased by using ME based hydrogel preparation.     

Disparity of in Vitro and in Vivo Oleic Acid-Enhanced β-Estradiol Percutaneous Absorption Across Human Skin

The permeation enhancing property of 5% oleic acid in ethanol on -estradiol was investigated in vitro and in vivo using symmetrical and asymmetrical side-by-side diffusion cells and the human skin sandwich flap, respectively. -Estradiol permeability in vitro and in vivo was similar in 75% ethanol (ETOH). Oleic acid (5%) did not alter -estradiol permeability in vivo but increased permeability sixfold in vitro in symmetrical diffusion cells. -Estradiol permeability in oleic acid was not different from that in ETOH, however, using asymmetrical diffusion cells. Stratum corneum-to-vehicle partition coefficients of -estradiol in the vehicles were similar, yet fourfold more steroid was detected in skin biopsies from the in vitro symmetrical diffusion cells. Thus, oleic acid increased -estradiol permeability in vitro only when skin was equilibrated with fatty acid. Attention to in vitro diffusion cell design and its relevance in vivo is critical to defining the mechanisms of enhanced solute permeation.