Nail morphology studies as assessments for onychomycosis treatment modalities

Poly(pseudo)rotaxanes formed by mixed micelles and α-cyclodextrin enhance terbinafine nail permeation to deeper layers

This work aimed to develop water-based formulations for onychomycosis topical treatment using micelles of small pegylated surfactants associated with α-cyclodextrin (αCD) to deliver terbinafine to the nail. Kolliphor® RH40 (RH40) and Gelucire® 48/16 (GEL) single and mixed micelles (RH40:GEL 1:1) were prepared. αCD was added to the surfactants dispersions to form poly(pseudo)rotaxanes (PPR). Formulations were characterized in terms of drug solubilization (3 to 34-fold increase), particle size (9–11 nm) and Z-potential (+0.3 − +1.96 mV), blood compatibility (non-hemolytic), rheological behavior (solid-like viscoelastic properties after 5–10% αCD addition), drug release and interaction with the nail plate. GEL micelles and surfactant-10% αCD PPRs notably hydrated the nail plate. The high viscosity of PPR led to a slower drug release, except for RH40:GEL +10% αCD that surprisingly released terbinafine faster. The RH40:GEL +10% αCD formulation delivered twice more amount of terbinafine to deeper regions of nail plate compared to other formulations. The results evidenced the potential of PPR formed by small pegylated surfactants as a water-based formulation for nail drug delivery.

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RH40, GEL and their mixed micelles increased 3-fold and 34-fold TB solubility in water and citrate buffer, respectively.

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Addition of αCD (5–10%) led to PPR formation and viscoelastic supramolecular gels without decrease in TB solubilization.

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PPR formulations with 10% αCD enhanced nail plate hydration, increasing its porosity.

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Compared to mixed micelles, PRP showed slower release rate but promoted TB accumulation in deeper regions of hooves.

Luliconazole Nail Lacquer for the Treatment of Onychomycosis: Formulation, Characterization and In Vitro and Ex Vivo Evaluation

Onychomycosis is the most common fungal infection of the nail affecting the skin under the fingertips and the toes. Currently, available therapy for onychomycosis includes oral and topical therapies, either alone or in combination. Oral antifungal medication has been associated with poor drug bioavailability and potential gastrointestinal and systemic side effects. The objective of this study was to prepare and evaluate the luliconazole nail lacquer (LCZ-NL) for the effective treatment of onychomycosis. In the current work, LCZ-NL was formulated in combination with penetration enhancers to overcome poor penetration. A 3² full factorial formulation design of experiment (DOE) was applied for optimization of batches with consideration of dependent (drying time, viscosity, and rate of drug diffusion) and independent (solvent ratio and film former ratio) variables. The optimized formulation was selected based on drying time, viscosity, and rate of drug diffusion. The optimized formulation was further evaluated for % non-volatile content assay, smoothness of flow, water resistance, drug content, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), in vitro drug release, ex vivo transungual permeation, antifungal efficacy, and stability study. The optimized LCZ-NL contained 70:30 solvent ratio and 1:1 film former ratio and was found to have ~ 1.79-fold higher rate of drug diffusion in comparison with LULY™. DSC and XRD studies confirmed that luliconazole retains its crystalline property in the prepared formulation. Antifungal study against Trichophyton spp. showed that LCZ-NL has comparatively higher growth inhibition than LULY™. Hence, developed LCZ-NL can be a promising topical drug delivery system for treating onychomycosis.

Enhanced nail delivery of voriconazole-loaded nanomicelles by thioglycolic acid pretreatment: A study of protein dynamics and disulfide bond rupture

This work aimed to select an effective penetration enhancer (PE) for nail pretreatment, develop voriconazole (VOR)-loaded nanomicelles, and evaluate their ability to deliver VOR to the nail. A complete analysis of nail protein dynamics, bond rupture, and microstructure was performed. Alternative methods as electron paramagnetic resonance (EPR) and the Ellman's reagent (DTNB) assay were also evaluated. Nanomicelles were produced and characterized. The PE hydrated the hooves, following the order: urea ≈ cysteine ≈ glycolic acid < thioglycolic acid (TGA) < NaOH. SEM images and methylene blue assay showed enlarged pores and roughness of porcine hooves after incubation with NaOH and TGA. EPR was demonstrated to be the most sensitive technique. DTNB assay quantified higher thiol groups for samples treated with TGA (p < 0.05). A stratigraphic analysis with Raman spectroscopy demonstrated that hooves treated with TGA presented a higher SH/SS ratio at the edges, affecting protein secondary structure. In vitro permeation studies demonstrated significant VOR permeation (29.44 ± 6.13 µg/cm²), 10-fold higher than previous studies with lipid nanoparticles. After TGA pretreatment, VOR permeation was further enhanced (3-fold). TGA pretreatment followed by VOR-loaded nanomicelles demonstrates a promising approach for onychomycosis treatment. The novel methods for protein analysis were straightforward and helpful.

Onychomycosis: Current Understanding and Strategies for Enhancing Drug Delivery into Human Nail Tissue

BACKGROUND

Onychomycosis is by far the most common finger or toe nail fungal infectious disease caused by dermatophytes, non-dermatophytic molds or yeast. It accounts for 50% of the total nail disorders, and affects patients physically, socially, and psychologically and can seriously influence their quality of life.

OBJECTIVES

Oral antifungals are routinely used to treat the nail fungal disease; however oral therapy is associated with severe side effects and longer treatment times. In recent years, drug delivery directly into the nail or nail bed has gained attention and various topical products have been tested that can cure the disease when applied topically or transungually. Nevertheless, drug penetration into and through the nail is not straightforward and requires chemicals to improve its permeability or by applying physical stress to promote drug penetration into and through the nail. This lucid review presents an overview of various causes of onychomycosis, current therapeutic approaches, and efforts aimed at increasing the permeability of nails through various strategies such as chemical, physical and mechanical methods for permeation enhancement.

CONCLUSION

Various strategies have been proposed for the treatment of onychomycosis, however, much research into a more precise and effective therapy is still required.

Raman Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy as Noninvasive Methods for Microstructural Alterations in Psoriatic Nails

Psoriasis is a chronic inflammatory disease associated with immune system dysfunction that can affect nails, with a negative impact on patient life quality. Usually, nail psoriasis is associated with skin psoriasis and is therefore relatively simple to diagnose. However, up to 10% of nail psoriasis occurs isolated and may be difficult to diagnose by means of current methods (nail biopsy, dermoscopy, video dermoscopy, capillaroscopy, ultrasound of the nails, etc.). Since the nail is a complex biological tissue, mainly composes of hard α-keratins, the structural and morphological techniques can be used to analyze the human fingernails. The aim of this study was to corroborate the information obtained using Raman spectroscopy with those obtained by scanning electron microscopy (SEM) and X-ray diffractometry and to assess the potential of these techniques as non-invasive dermatologic diagnostic tools and an alternative to current methods.

Treatment and management strategies of onychomycosis

Onychomycosis is one of the most prevalent and severe nail fungal infections, which is affecting a wide population across the globe. It leads to variations like nail thickening, disintegration and hardening. Oral and topical drug delivery systems are the most desirable in treating onychomycosis, but the efficacy of the results is low, resulting in a relapse rate of 25-30%. Due to systemic toxicity and various other disadvantages associated with oral therapy like gastrointestinal, hepatotoxicity, topical therapy is commonly used. Topical therapy improves patient compliance and reduces the cost of treatment. However, due to poor penetration of topical therapy across the nail plate, research is focused on different chemical, mechanical and physical methods to improve drug delivery. Penetration enhancers like Thioglycolic acid, Hydroxypropyl-β-cyclodextrin (HP-β-CD), Sodium lauryl sulfate (SLS), carbocysteine, N-acetylcysteine etc. have shown results enhancing the drug penetration across the nail plate. Results with physical techniques such as iontophoresis, laser and Photodynamic therapy are quite promising, but the long-term suitability of these devices is in need to be determined. In this article, a brief analysis of the treatment procedures, factors affecting drug permeation across nail plate, chemical, mechanical and physical devices used to increase the drug delivery through nails for the onychomycosis management has been achieved.

Recent Patents on Permeation Enhancers for Drug Delivery Through Nails

The human nail is a unique barrier with a keratinized constitution that favors protection and fine touch. However, many disorders can affect the nail, among them, are the onychomycosis and psoriasis. Systemic oral therapy has been applied to treat these diseases, even presenting disadvantages, including side effects, drug interactions, contraindications, toxicity, high cost and low patient compliance. A great option to succeed in dealing with the problems associated with oral therapy is the topical administration of drugs. However, nail composition, low diffusion through ungual route and reduced tissue bioavailability for topical treatments are limiting factors. These drawbacks can be overcome by promoting penetration through the nails by employing penetration enhancers. The review focuses on patents that highlight permeation enhancers applied to nail drug delivery for the treatment of onychomycosis and psoriasis. Literature and patent searches were conduced regarding the topic of interest. The substantial literature and patent search revealed that permeation enhancers, especially chemicals, are great strategies for promoting the ungual delivery of drugs. Nail topical therapy containing permeation enhancers is an attractive option for delivering localized treatments.

Chemical and physical strategies in onychomycosis topical treatment: A review

Onychomycosis is a fungal infection of the fingernails or toenails caused by dermatophytes, nondermatophytes, moulds, and yeasts. This condition affects around 10-30% people worldwide, negatively influencing patients' quality of life, with severe outcomes in some cases. Since the nail unit acts as a barrier to exogenous substances, its physiological features hampers drug penetration, turning the onychomycosis treatment a challenge. Currently, there are several oral and topical therapies available; nevertheless, cure rates are still low and relapse rates achieves 10-53%. Also, serious side effects may be developed due to long-term treatment. In light of these facts, researchers have focused on improving topical treatments, either by modifying the vehicle or by using some physical technique to improve drug delivery trough the nail plate, hence increasing therapy effectiveness. Therefore, the aim of this paper is to explain these novel alternative approaches. First, the challenges for drug ungual penetration are presented. Then, the chemical and physical strategies developed for overcoming the barriers for drug penetration are discussed. We hope that the information gathered may be useful for the development of safer and more effective treatments for onychomycosis.

Evaluation of Laser-Assisted Trans-Nail Drug Delivery with Optical Coherence Tomography

The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. The nail plate consists of three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO₂ laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. We utilized optical coherence tomography (OCT) for real-time monitoring of the laser–skin tissue interaction, sparing the patient from an invasive surgical sampling procedure. The time-dependent OCT intensity variance was used to observe drug diffusion through an induced MAZ array. Subsequently, nails were treated with cream and liquid topical drugs to investigate the feasibility and diffusion efficacy of laser-assisted drug delivery. Our results show that fractional CO₂ laser improves the effectiveness of topical drug delivery in the nail plate and that OCT could potentially be used for in vivo monitoring of the depth of laser penetration as well as real-time observations of drug delivery.

Application of Hansen Solubility Parameters to predict drug-nail interactions, which can assist the design of nail medicines

We hypothesised that Hansen Solubility Parameters (HSPs) can be used to predict drug-nail affinities. Our aims were to: (i) determine the HSPs (δD, δP, δH) of the nail plate, the hoof membrane (a model for the nail plate), and of the drugs terbinafine HCl, amorolfine HCl, ciclopirox olamine and efinaconazole, by measuring their swelling/solubility in organic liquids, (ii) predict nail-drug interactions by comparing drug and nail HSPs, and (iii) evaluate the accuracy of these predictions using literature reports of experimentally-determined affinities of these drugs for keratin, the main constituent of the nail plate and hoof. Many solvents caused no change in the mass of nail plates, a few solvents deswelled the nail, while others swelled the nail to varying extents. Fingernail and toenail HSPs were almost the same, while hoof HSPs were similar, except for a slightly lower δP. High nail-terbinafine HCl, nail-amorolfine HCl and nail-ciclopirox olamine affinities, and low nail-efinaconazole affinities were then predicted, and found to accurately match experimental reports of these drugs' affinities to keratin. We therefore propose that drug and nail Hansen Solubility Parameters may be used to predict drug-nail interactions, and that these results can assist in the design of drugs for the treatment of nail diseases, such as onychomycosis and psoriasis. To our knowledge, this is the first report of the application of HSPs in ungual research.

Novel nail penetration enhancer containing vesicles "nPEVs" for treatment of onychomycosis

CONTEXT

The systemic treatment of onychomycosis has been hampered by the reported side effects of antifungals in addition to the limited blood circulation to the affected nails. Topical ungual treatment would circumvent the limitations of systemic onychomycosis treatment.

OBJECTIVE

Preparation and characterization of nail penetration enhancer containing nanovesicles (nPEVs) loaded with sertaconazole for topical treatment of onychomycosis.

MATERIALS AND METHODS

nPEVs were prepared using different nail penetration enhancers (N-acetyl-L-cysteine, thioglycolic acid, thiourea and ethanol) by the thin film hydration method, and characterized for their particle size, zeta potential, entrapment efficiency (EE%), elasticity, viscosity, physical stability and morphology. The selected nPEVs formula and the marketed Dermofix® cream were compared in terms of nail hydration, transungual drug uptake and antifungal activity against Trichophyton rubrum.

RESULTS

N-acetyl-l-cysteine was the optimum nail penetration enhancer for incorporation within vesicles. nPEVs showed high EE% of sertaconazole ranging from 77 to 95%, a size ranging from 38-538 nm and a zeta potential ranging from +48 to +72 mV. The selected nPEVs formula displayed spherical morphology and good storage stability. Compared to the conventional marketed cream, the selected nPEVs formula showed 1.4-folds higher hydration and drug uptake enhancement into nail clippings. Furthermore, it showed significantly higher zone of inhibition for Trichophyton rubrum (20.9 ± 0.25 mm) than the marketed cream (11.6 ± 0.44 mm).

CONCLUSION

Nail penetration enhancer containing nanovesicles (nPEVs) present a very promising option, worthy of clinical experimentation on onychomycotic patients.

Transungual permeation: current insights

Nail disorders are beyond cosmetic concern; besides discomfort in the performance of daily chores, they disturb patients psychologically and affect their quality of life. Fungal nail infection (onychomycosis) is the most prevalent nail-related disorder affecting a major population worldwide. Overcoming the impenetrable nail barrier is the toughest challenge for the development of efficacious topical ungual formulation. Sophisticated techniques such as iontophoresis and photodynamic therapy have been proven to improve transungual permeation. This article provides an updated and concise discussion regarding the conventional approach and upcoming novel approaches focused to alter the nail barrier. A comprehensive description regarding preformulation screening techniques for the identification of potential ungual enhancers is also described in this review while highlighting the current pitfalls for the development of ungual delivery.

Insights into drug delivery across the nail plate barrier

Topical therapy is at the forefront in treating nail ailments (especially onychomycosis and nail psoriasis) due to its local effects, which circumvents systemic adverse events, improves patient compliance and reduces treatment cost. However, the success of topical therapy has been hindered due to poor penetration of topical therapeutics across densely keratinized nail plate barrier. For effective topical therapy across nail plate, ungual drug permeation must be enhanced. Present review is designed to provide an insight into prime aspects of transungual drug delivery viz. nail structure and physiology, various onychopathies, techniques of nail permeation enhancement and in vitro models for trans-nail drug permeation studies. Updated list of drug molecules studied across the nail plate and key commercial products have been furnished with sufficient depth. Patents pertinent to, and current clinical status of transungual drug delivery have also been comprehensively reviewed. This is the first systematic critique encompassing the detailed aspects of transungual drug delivery. In our opinion, transungual drug delivery is a promising avenue for researchers to develop novel formulations, augmenting pharmaceutical industries to commercialize the products for nail disorders.

An update on treatment of onychomycosis

Onychomycosis (OM) is a fungal infection of the nail plate or nail bed which is highly prevalent in the general population and also responsible for significant morbidity. The condition needs to be treated in view of the physical and emotional handicap it produces. The peculiarities of the nail apparatus in health and disease lead to difficulties in being able to successfully treat this condition. Hence, the very same antifungals which produce high cure rates in skin infections are rendered less efficacious in nail disease. Low cure rates and high relapse rates even with highly efficacious antifungals have lead to an increasing interest in exploring newer treatment options which can ensure drug penetration, drug persistence, mycological cure and effective prevention of relapse. The current review aims to summarize our current status of knowledge about the treatment options for OM. It also summarizes the newer areas of research especially with respect to devices related therapies; physical measures to enhance penetration through nail; and development and evaluation of synergistic combinations.

Ungual and transungual drug delivery

Topical therapy is desirable in treatment of nail diseases like onychomycosis (fungal infection of nail) and psoriasis. The topical treatment avoids the adverse effects associated with systemic therapy, thereby enhancing the patient compliance and reducing the treatment cost. However the effectiveness of the topical therapies has been limited due to the poor permeability of the nail plate to topically applied therapeutic agents. Research over the past one decade has been focused on improving the transungual permeability by means of chemical treatment, penetration enhancers, mechanical and physical methods. The present review is an attempt to discuss the different physical and chemical methods employed to increase the permeability of the nail plate. Minimally invasive electrically mediated techniques such as iontophoresis have gained success in facilitating the transungual delivery of actives. In addition drug transport across the nail plate has been improved by filing the dorsal surface of the nail plate prior to application of topical formulation. But attempts to improve the trans-nail permeation using transdermal chemical enhancers have failed so far. Attempts are on to search suitable physical enhancement techniques and chemical transungual enhancers in view to maximize the drug delivery across the nail plate.

Effect of a novel penetration enhancer on the ungual permeation of two antifungal agents

OBJECTIVES

The aim of this study was to demonstrate the effect of a novel permeation enhancer system using two existing marketed nail lacquers and the delivery of terbinafine through human nail samples in vitro.

METHODS

Initially a modified Franz cell was used, where sections of human nail serve as the barrier through which drug penetrates into an agar-filled chamber infected with dermatophytes. A second study was performed using a novel infected nail model where dermatophytes are incubated with and grow into human nail and ATP levels are used as biological marker for antimicrobial activity.

KEY FINDINGS

The novel permeation enhancing system increased the permeation of both existing drugs formulated in nail lacquers and terbinafine through human nail sections mounted in a modified Franz cell. Furthermore the ATP assay confirmed that the system also enhanced the permeation of terbinafine through infected cadaver nail resulting in a decrease in ATP levels equivalent to those of uninfected negative control samples.

CONCLUSIONS

This study has clearly demonstrated that the use of a novel permeation enhancing system, which fundamentally alters the chemical structure of the nail, not only enhances the efficacy of the existing topical formulations but also enables the delivery and efficacy of terbinafine when applied ungually. Such a topically applied system has the possibility of overcoming the systemic side effects when terbinafine is delivered orally.

Mechanistic study of electroosmotic transport across hydrated nail plates: effects of pH and ionic strength

The objective of this study was to investigate the effects of pH and ionic strength on electroosmotic transport in transungual iontophoresis. Transungual iontophoretic transport of model neutral permeants mannitol (MA) and urea (UR) across fully hydrated human nail plates in phosphate-buffered saline of different pH and ionic strengths were investigated in vitro. Two protocols were involved in the transport experiments with each protocol divided into stages including passive and iontophoresis transport at 0.1 and/or 0.3 mA. Nail plate electrical resistance and water uptake of nail clippings were measured at various pH and ionic strengths. In the pH study, electroosmosis enhanced the anodal transport of MA at pH 9 and cathodal transport at pH 3. The Peclet numbers of MA were more than two times higher than those of UR under these conditions. No significant electroosmosis enhancement was observed for MA and UR at pH 5. In the ionic strength study, a decrease in solution ionic strength from 0.7 to 0.04 M enhanced electroosmotic transport. Nail electrical resistance increased with decreasing the ionic strength of the equilibrating solution, but reached a plateau when the ionic strength was less than approximately 0.07 M. Solution pH and ionic strength had no significant effect on nail hydration. Under the studied pH and ionic strength conditions, the effects of electroosmosis were small compared to the direct-field effects in transungual iontophoretic transport of small to moderate size permeants.

Pharmaceutical Applications of Hot-Melt Extrusion: Part I

Interest in hot-melt extrusion techniques for pharmaceutical applications is growing rapidly with well over 100 papers published in the pharmaceutical scientific literature in the last 12 years. Hot-melt extrusion (HME) has been a widely applied technique in the plastics industry and has been demonstrated recently to be a viable method to prepare several types of dosage forms and drug delivery systems. Hot-melt extruded dosage forms are complex mixtures of active medicaments, functional excipients, and processing aids. HME also offers several advantages over traditional pharmaceutical processing techniques including the absence of solvents, few processing steps, continuous operation, and the possibility of the formation of solid dispersions and improved bioavailability. This article, Part I, reviews the pharmaceutical applications of hot-melt extrusion, including equipment, principles of operation, and process technology. The raw materials processed using this technique are also detailed and the physicochemical properties of the resultant dosage forms are described. Part II of this review will focus on various applications of HME in drug delivery such as granules, pellets, immediate and modified release tablets, transmucosal and transdermal systems, and implants.

Influence of Tartaric Acid on the Bioadhesion and Mechanical Properties of Hot-Melt Extruded Hydroxypropyl Cellulose Films for the Human Nail

The objective of this study was to investigate the influence of tartaric acid (TTA) on the bioadhesive, moisture sorption, and mechanical properties of hot-melt-extruded (HME) hydroxypropyl cellulose (HPC) films containing polymer additives. Two Klucel EF and LF batches (HPC, MW: 80000 and 95000, respectively) containing the model antifungal drug ketoconazole (one batch of each MW with and without TTA 4%) were prepared into films by HME using a Killion extruder (Model KLB-100). The bioadhesive properties of the HPC films, with and without TTA, were investigated ex vivo on the human nails. The parameters measured were work of adhesion and peak adhesion force (PAF). A statistically significant increase in both the area under the curve (AUC) and PAF was seen for the HME films containing TTA than those without TTA. Moisture content of hot-melt extruded HPC films was determined using thermogravimetric analysis (TGA). TGA data collected at the two-week interval (25 degrees C/60% RH), measured higher moisture content for the TTA-containing films than those without TTA. Tensile strength and percent elongation were determined utilizing a TA.XT2i Texture Analyzer(R) equipped with a 50-kg load cell, TA-96 grips, and Texture Expert software. TTA functioned as an effective plasticizer, increasing percent elongation and decreasing tensile strength of the HPC films. TTA could potentially be a candidate for transnail applications in film devices prepared by hot-melt extrusion technology.

Chemical method to enhance transungual transport and iontophoresis efficiency

Transungual transport is hindered by the inherent small effective pore size of the nail even when it is fully hydrated. The objectives of this study were to determine the effects of chemical enhancers thioglycolic acid (TGA), glycolic acid (GA), and urea (UR) on transungual transport and iontophoresis efficiency. In vitro passive and iontophoretic transport experiments of model permeants mannitol (MA), UR, and tetraethylammonium (TEA) ion across the fully hydrated, enhancer-treated and untreated human nail plates were performed in phosphate-buffered saline. The transport experiments consisted of several stages, alternating between passive and anodal iontophoretic transport at 0.1mA. Nail water uptake experiments were conducted to determine the water content of the enhancer-treated nails. The effects of the enhancers on transungual electroosmosis were also evaluated. Nails treated with GA and UR did not show any transport enhancement. Treatment with TGA at 0.5M enhanced passive and iontophoretic transungual transport of MA, UR, and TEA. Increasing the TGA concentration to 1.8M did not further increase TEA iontophoresis efficiency. The effect of TGA on the nail plates was irreversible. The present study shows the possibility of using a chemical enhancer to reduce transport hindrance in the nail plate and thus enhance passive and iontophoretic transungual transport.

Transungual iontophoretic transport of polar neutral and positively charged model permeants: effects of electrophoresis and electroosmosis

Transungual iontophoretic transport of model neutral permeants mannitol (MA), urea (UR), and positively charged permeant tetraethylammonium ion (TEA) across fully hydrated human nail plates at pH 7.4 were investigated in vitro. Four protocols were involved in the transport experiments with each protocol divided into stages including passive and iontophoresis transport of 0.1 and 0.3 mA. Water and permeant uptake experiments of nail clippings were also conducted to characterize the hydration and binding effects of the permeants to the nails. Iontophoresis enhanced the transport of MA and UR from anode to cathode, but this effect (electroosmosis) was marginal. The transport of TEA was significantly enhanced by anodal iontophoresis and the experimental enhancement factors were consistent with the Nernst-Planck theory predictions. Hindered transport was also observed and believed to be critical in transungual delivery. The barrier of the nail plates was stable over the time course of the study, and no significant electric field-induced alteration of the barrier was observed. The present results with hydrated nail plates are consistent with electrophoresis-dominant (the direct field effect) transungual iontophoretic transport of small ionic permeants with small contribution from electroosmosis.

Topical application of acidified nitrite to the nail renders it antifungal and causes nitrosation of cysteine groups in the nail plate

BACKGROUND

Topical treatment of nail diseases is hampered by the nail plate barrier, consisting of dense cross-linked keratin fibres held together by cysteine-rich proteins and disulphide bonds, which prevents penetration of antifungal agents to the focus of fungal infection. Acidified nitrite is an effective treatment for tinea pedis. It releases nitric oxide (NO) and other NO-related species. NO can react with thiol (-SH) groups to form nitrosothiols (-SNO).

OBJECTIVES

To determine whether acidified nitrite can penetrate the nail barrier and cure onychomycosis, and to determine whether nitrosospecies can bind to the nail plate.

METHODS

Nails were treated with a mixture of citric acid and sodium nitrite in a molar ratio of 0.54 at either low dose (0.75%/0.5%) or high dose (13.5%/9%). Immunohistochemistry, ultraviolet-visible absorbance spectroscopy and serial chemical reduction of nitrosospecies followed by chemiluminescent detection of NO were used to measure nitrosospecies. Acidified nitrite-treated nails and the nitrosothiols S-nitrosopenicillamine (SNAP) and S-nitrosoglutathione (GSNO) were added to Trichophyton rubrum and T. mentagrophytes cultures in liquid Sabouraud medium and growth measured 3 days later. Thirteen patients with positive mycological cultures for Trichophyton or Fusarium species were treated with topical acidified nitrite for 16 weeks. Repeat mycological examination was performed during this treatment time.

RESULTS

S-nitrothiols were formed in the nail following a single treatment of low- or high-dose sodium nitrite and citric acid. Repeated exposure to high-dose acidified nitrite led to additional formation of N-nitrosated species. S-nitrosothiol formation caused the nail to become antifungal to T. rubrum and T. mentagrophytes. Antifungal activity was Cu(2+) sensitive. The nitrosothiols SNAP and GSNO were also found to be antifungal. Topical acidified nitrite treatment of patients with onychomycosis resulted in > 90% becoming culture negative for T. rubrum.

CONCLUSIONS

Acidified nitrite cream results in the formation of S-nitrosocysteine throughout the treated nail. Acidified nitrite treatment makes a nail antifungal. S-nitrosothiols, formed by nitrosation of nail sulphur residues, are the active component. Acidified nitrite exploits the nature of the nail barrier and utilizes it as a means of delivery of NO/nitrosothiol-mediated antifungal activity. Thus the principal obstacle to therapy in the nail becomes an effective delivery mechanism.

In vitro transungual permeation of ciclopirox from a hydroxypropyl chitosan-based, water-soluble nail lacquer

Commercial antimycotic nail lacquers are commonly based on water-insoluble resins. The present study was aimed at evaluating a novel, experimental nail lacquer (P-3051, Polichem SA, Lugano, Switzerland) based on the water-soluble film-forming agent hydroxypropyl chitosan (HPCH). The in vitro permeation of ciclopirox (CPX) from P-3051 and from a commercial, water-insoluble lacquer based on a vinyl resin (Penlac, Aventis Pharma), was investigated using thin membranes obtained from bovine hooves, an accepted model for human nails. Similar CPX permeation fluxes at steady state through the membranes, but significantly different lag times were observed for P-3051 and Penlac, when these were tested as dry films. The formulations thus appeared to influence only the time required by CPX to saturate the membrane, and not the final drug concentration gradient in the membrane. Permeation experiments performed on the same membranes and on hairless mouse skin with P-3051 and with a similar, HPCH-free vehicle (ERV), both tested in liquid form, disproved the possibility that HPCH might act as a permeation enhancer for CPX in either substrate. The possible reasons for the greater efficiency of the HPCH vehicle in terms of CPX transfer from the vehicle itself to the keratin membrane are discussed. This effect might be tentatively attributed to a particular affinity of HPCH for the membrane, resulting in intimate contact and strong adhesion of the HPCH lacquer to the keratin substrate.

Influence of human nail etching for the assessment of topical onychomycosis therapies

The purpose of this investigation was to study the physico-chemical properties of hot-melt extruded films containing ketoconazole and to determine the influence of 'nail etching' on film bioadhesion and drug permeability for the assessment of topical onychomycosis therapies. Hot-melt extrusion (HME) was used to prepare films containing 20% w/w ketoconazole. Ketoconazole 0.125% gel was also prepared using Carbopol 974P NF. Films were processed at a temperature range of 115-120 degrees C utilizing a Killion extruder (KLB-100), and were evaluated for post-extrusion drug content, content uniformity, bioadhesion, thermal behavior and nail drug permeation. The extruded films demonstrated excellent content uniformity and post-processing drug content. Tensile and peel tests were recorded to determine the bioadhesive profiles. In this study, work of adhesion and peak adhesive force determinations using the peel tests provided more sensitive results for evaluating the bioadhesivity of the HME films than the tensile tests. The in vitro permeability profiles have demonstrated, that nail samples treated with an 'etchant' demonstrated a significant increase in drug permeability compared to control. Differential scanning calorimetry (DSC) thermograms indicated that ketoconazole was in solid solution within the HME films. These findings are encouraging for the future design and formulation of novel drug delivery systems for the topical treatment of onychomycosis.

The influence of guaifenesin and ketoprofen on the properties of hot-melt extruded polyethylene oxide films

Films containing polyethylene oxide (PEO) and a model drug, either guaifenesin (GFN) or ketoprofen (KTP), were prepared by hot-melt extrusion. The thermal properties of the hot-melt extruded films were investigated using differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) was used to examine the surface morphology of the films, and wide angle X-ray diffraction (XRD) was used to investigate the crystalline properties of the polymer, drugs and physical mixtures as well as the solid state structure of the films. The stability of the polymer was studied using gel permeation chromatography. The mechanical properties, including percent elongation and tensile strength of the films, were determined on an Instron according to American Society for Testing Materials (ASTM) procedures. The Hansen solubility parameter was calculated using the Hoftyzer or van Krevelen method to estimate the likelihood of drug--polymer miscibility. Both GFN and KTP were stable during the extrusion process. Melting points corresponding to the crystalline drugs were not observed in the films. Crystallization of GFN on the surface of the film was observed at all concentrations studied, however KTP crystallization did not occur until reaching the 15% level. Guaifenesin and ketoprofen were found to decrease drive load, increase PEO stability and plasticize the polymer during extrusion. The Hansen solubility parameters predicted miscibility between PEO and KTP and poor miscibility between PEO and GFN. The predictions of the solubility parameters were in agreement with the XRD and SEM results. The percent elongation decreased with increasing GFN concentrations and significantly increased with increasing levels of KTP. Both GFN and KTP decreased the tensile strength of the extruded film.