Improved efficacy in onychomycosis therapy

Contemporary Techniques and Potential Transungual Drug Delivery Nanosystems for The Treatment of Onychomycosis

The humanoid nail is considered an exceptional protective barrier that is formed mainly from keratin. Onychomycosis is the cause of 50% of nail infections that is generally caused by dermatophytes. Firstly, the infection was regarded as a cosmetic problem but because of the tenacious nature of onychomycosis and its relapses, these infections have attracted medical attention. The first line of therapy was the oral antifungal agents which were proven to be effective; nevertheless, they exhibited hepato-toxic side effects, alongside drug interactions. Following, the opportunity was shifted to the topical remedies, as onychomycosis is rather superficial, yet this route is hindered by the keratinized layers in the nail plate. A potential alternative to overcome the obstacle was applying different mechanical, physical, and chemical methods to boost the penetration of drugs through the nail plate. Unfortunately, these methods might be expensive, require an expert to be completed, or even be followed by pain or more serious side effects. Furthermore, topical formulations such as nail lacquers and patches do not provide enough sustaining effects. Recently, newer therapies such as nanovesicles, nanoparticles, and nanoemulsions have emerged for the treatment of onychomycosis that provided effective treatment with possibly no side effects. This review states the treatment strategies such as mechanical, physical, and chemical methods, and highlights various innovative dosage forms and nanosystems developed in the last 10 years with a focus on advanced findings regarding formulation systems. Furthermore, it demonstrates the natural bioactives and their formulation as nanosystems, and the most relevant clinical outcomes.

Therapeutic treatment strategies for the management of onychomycosis: a patent perspective

INTRODUCTION

Onychomycosis, a multifactorial fungal infection of the nails, shows a global prevalence of about 5.5% and is responsible for 50% of all nail infections. To develop effective management strategies, it is necessary to understand the etiology, pathophysiology, and risk factors of onychomycosis. Oral route of drug delivery is one of the routes utilized to deliver anti-fungal agents, but, has its own limitations like longer duration of treatment, increased adverse effects, and potential for drug interaction. The ungual route has received greater attention due to its localized, non- invasive action and improved patient compliance.

AREAS COVERED

This review comprehensively discusses conventional onychomycosis therapies and patented novel drug delivery systems for the management of onychomycosis including chemical permeation enhancers, non-particulate drug delivery systems, penetration enhancing devices etc., Databases such as PubMed, ResearchGate, and Google Patents were searched by using the keywords onychomycosis and trans-ungual drug delivery.

EXPERT OPINION

Enormous research has been conducted and is still ongoing to find the best possible novel drug delivery system for onychomycosis management. Approaches like incorporation of herbal constituents in nano-formulations, inkjet printing, laser devices, iontophoretic techniques, etc. can be employed to make safe and effective drug delivery systems which are regulatory compliant.

Response surface methodological approach for optimization of photodynamic therapy of onychomycosis using chlorin e6 loaded nail penetration enhancer vesicles

Antimicrobial photodynamic inactivation (aPDI) has a tremendous potential as an alternative therapeutic modality to conventional antifungals in treatment of onychomycosis, yet the nail barrier properties and the deep-seated nature of fungi within the nails remain challenging. Therefore, the aim of this study was to prepare, optimize, and characterize Chorin e6 (Ce6) nail penetration enhancer containing vesicles (Ce6-nPEVs) and evaluate their photodynamic mediated effect against Trichophyton rubrum (T.rubrum); the main causative agent of onychomycosis. Optimization of the particle size and encapsulation efficiency of nPEVs was performed using a four-factor two-level full factorial design. The transungual delivery potential of the selected formulation was assessed in comparison with the free drug. The photodynamic treatment conditions for T.rubrum aPDI by free Ce6 was optimized using response surface methodology based on Box-Behnken design, and the aPDI effect of the selected Ce6-nPEVs was evaluated versus the free Ce6 at the optimized condition. Results showed that formulations exhibited high encapsulation efficiency for Ce6 ranging from 79.4 to 98%, particle sizes ranging from 225 to 859 nm, positive zeta potential values ranging from +30 to +70 mV, and viscosity ranging from 1.26 to 3.43 cP. The predominant parameters for maximizing the encapsulation efficiency and minimizing the particle size of Ce6-nPEVs were identified. The selected formulation showed 1.8-folds higher nail hydration and 2.3 folds improvement in percentage of Ce6 up-taken by nails compared to the free drug. Results of the microbiological study confirmed the reliability and adequacy of the Box-Behnken model, and delineated Ce6 concentration and incubation time as the significant model terms. Free Ce6 and Ce6-nPEVs showed an equipotent in vitro fungicidal effect on T.rubrum at the optimized conditions, however Ce6-nPEVs is expected to show a differential effect at the in vivo level where the advantage of the enhanced nail penetration feature will be demonstrated.

Fungal Lung

Foot and nail care specialists spend a great portion of their day using nail drills to reduce nail thickness and smooth foot calluses. This process generates a large amount of dust, some of which is small enough to breathe in and deposit into the deepest regions of the respiratory tract, potentially causing health problems. Foot and nail dust often contains fungi, from both fungus-infected and healthy-appearing nails. Although the majority of healthy individuals can tolerate inhaled fungi, the immune systems of older, immunocompromised, and allergy-prone individuals often react using the inflammatory T helper cell type 2 pathway, leading to mucus overproduction, bronchoconstriction, and, in severe cases, lung tissue damage. To protect vulnerable podiatry professionals, wearing a surgical mask, using a water spray suppression system on nail drills, installing air filtration systems, and considering drilling technique can help reduce exposure to nail dust.

Poloxamer 407 Based Gel Formulations for Transungual Delivery of Hydrophobic Drugs: Selection and Optimization of Potential Additives

The current study aimed to develop poloxamer 407 (P407) gel for transungual delivery of antifungal hydrophobic drugs with sufficient gel strength and drug loading. Gel strength and drug loading of P407 gel was improved by use of functional additives. Hydration enhancement effect was used to select optimum nail penetration enhancer. Face-centered central composite design (FCCCD) was used to observe the effect of the selected penetration enhancer (thioglycolic acid (TGA)) and cosolvent (ethanol) on gelation behavior to develop formulation with enough loading of hydrophobic drug, i.e., terbinafine HCl (TBN), and its permeation across the nail plate without compromising on gel strength. It was observed that increasing concentration of P407 and TGA significantly reduced gelation temperature and enhanced the gel strength of P407 gel and can be used to improve P407 gel strength. Under the scanning electron microscope, the significant effect of TGA as an ungual penetration enhancer was observed on the morphology of the nail plate. Optimized P407 gel prepared with modified cold method showed a gelation temperature of 8.7 ± 0.16 °C, gel strength of 122 ± 7.5 s and drug loading of 1.2% w/w, which was four times more than the drug loading in the gels prepared with conventional cold method. Rheological behavior was pseudoplastic with 47.75 ± 3.48% of gel erosion after 12 washings and 67.21 ± 2.16% of drug release after 12 h. A cumulative amount of TBN permeated from P407 gel with and without PE after 24 h was 27.30 ± 4.18 and 16.69 ± 2.31 µg/cm², respectively. Thioglycolic acid can be used as a nail penetration enhancer without the chemical modification or addition of extra additives while retaining the gel strength. Water miscible cosolvents with moderate evaporability such as ethanol, can be incorporated to P407 gel by minor modification in method of preparation to load the required dose of hydrophobic drugs. Developed P407 gel formulation with sufficient gel strength and drug loading will be a promising carrier for transungual delivery of hydrophobic antifungal agents.

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.

In Vitro Combination Effect of Topical and Oral Anti-Onychomycosis Drugs on Trichophyton rubrum and Trichophyton interdigitale

To evaluate the combination effects of anti-onychomycosis drugs, the minimum inhibitory concentrations of topical (efinaconazole, luliconazole, and tavaborole) and oral (itraconazole and terbinafine) drugs for Trichophyton rubrum and Trichophyton interdigitale (8 each, with a total of 16 strains) were determined using the microdilution checkerboard technique based on the Clinical and Laboratory Standard Institute guidelines. No antagonism was observed between the topical and oral drugs against all the tested strains. Efinaconazole with terbinafine exerted a synergistic effect on 43.8% of the strains tested (7/16 strains) and efinaconazole with itraconazole on 12.5% (2/16 strains). Conversely, luliconazole showed no synergistic effect with terbinafine but was synergistically effective with itraconazole against 31.3% of the strains (5/16 strains). Tavaborole showed no synergistic effect with terbinafine and was synergistically effective with itraconazole against 18.8% of the strains (3/16 strains). The results suggest that a combination of topical and oral drugs could be a potential clinical option for onychomycosis treatment, and overall, the efinaconazole and oral drug combination would be the most advantageous among the tested combinations.

Potential of Chemical and Physical Enhancers for Transungual Delivery of Amorolfine Hydrochloride

Topical monotherapy of nail infection is limited by poor drug permeability into the human nail plate. Numerous substances and methods are applied to improve the antifungal agent delivery across the nail plate. This work aimed to evaluate the effect of chemical and physical enhancers on the accumulation and permeation of amorolfine hydrochloride through human nail clippings. Polymeric nail lacquers with Eudragit E100 were developed as a potentially suitable delivery system for amorolfine hydrochloride. Incorporating thioglycolic acid and urea into formulations provided increased accumulation of antifungal agent in nail layers of up to 100% and 57%, respectively. Structural changes of nail barrier, induced by fractional CO₂ laser, were visualized by microscopy. The permeation of amorolfine hydrochloride through the nail increased twofold when thioglycolic acid-containing formulation was applied and the nail was pretreated with a fractional CO₂ laser. The results suggest that this novel combination of enhancers has the potential to be an effective option for topical drug delivery through the nail, and increased the efficacy of treatment.

A pilot, layerwise, ex vivo evaluation of the antifungal efficacy of amorolfine 5% nail lacquer vs other topical antifungal nail formulations in healthy toenails

BACKGROUND

Studies investigating the penetration of amorolfine through the nail have shown the highest concentration in the uppermost layer and measurable antifungal activity even in the lower layers of the nail.

OBJECTIVES

This pilot, ex vivo study compared the penetration of antifungal concentrations of amorolfine 5% nail lacquer in different layers of healthy, human cadaver toenails with that of terbinafine 10% nail solution, ciclopirox 8% nail lacquer and naftifine 1% nail solution. Moreover, the effect of nail filing prior to application on the penetration of amorolfine 5% was assessed.

METHODS

Unfiled (n = 3) and filed (n = 3) nails were used for each antimycotic agent and amorolfine 5% nail lacquer, respectively. Twenty-four hours after topical application, the nails were sliced (10 μm), solubilised and added to agar plates seeded with Trichophyton rubrum. Zones of growth inhibition were measured.

RESULTS

Only amorolfine penetrated the nails at sufficient concentrations to inhibit growth of T rubrum at different nail depths. In contrast, the comparators did not show antifungal efficacy. Nail filing resulted in larger zones of inhibition for amorolfine compared with those of intact nails.

CONCLUSIONS

Unlike its comparators, a single application of amorolfine 5% nail lacquer resulted in antifungal efficacy within the nail plate. Nail filing increased the antifungal efficacy of amorolfine 5% nail lacquer.

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.

COMBINATION ANTIFUNGAL THERAPY FOR ONYCHOMYCOSIS

Onychomycosis is a fungal infection of the nail unit including the nail matrix, the nail bed and the nail plate by both dermatophyte and non-dermatophyte agents. It is disturbs not only cosmetic disfigurement, but also it may have an impact on patients’ emotional, social and occupational functioning, finally affecting the overall quality of life. The incidence rate tends to increase, management of onychomycosis is still challenging. Important problems regarding antifungal monotherapy have experienced many failures and recurrences. In general, pharmacological approaches for onychomycosis can be topical or oral antifungal. Antifungal monotherapies often lead to failure treatment, also high incidence of recurrence. One strategy for this problem is a combination antifungal therapy. In vitro studies show the synergistic effect of using combination two antifungals (both oral antifungal or combination topical and oral antifungal), hence it is mycologically or clinically expected to increase the success rate of onychomycosis therapy. This review tries to evaluate the previous study exploring the effectiveness of antifungal combination therapies on onychomycosis. Two oral antifungals usually used are terbinafine as fungicidal agent and itraconazole as fungistatic agent. There is combination between topical and oral antifungal such as itraconazole or terbinafine with amorolfine or ciclopirox, also other combination like griseofulvin and amorolfone or tioconazole. All the combination therapies show better result than monotherapy alone, but it is still difficult to conclude whether antifungal combinations in onychomycosis will increase effectiveness due to variations in therapeutic duration, result definition, and statistical evaluation on existing studies. Further research is required with longer duration of observation, uniform patient criteria and definition of success, random control and blinding to minimize bias.

Clinical laser treatment of toenail onychomycoses

Onychomycoses are fungal infections of the fingernails or toenails having a prevalence of 3% among adults and accounts for 50% of nail infections. It is caused by dermatophytes, non-dermatophyte filamentous fungi, and yeasts. Compressions and microtraumas significantly contribute to onychomycosis. Laser and photodynamic therapies are being proposed to treat onychomycosis. Laser light (1064 nm) was used to treat onychomycosis in 156 affected toenails. Patients were clinically followed up for 9 months after treatment. Microbiological detection of fungal presence in lesions was accomplished. A total of 116 samples allowed the isolation of at least a fungus. Most of nails were affected in more than two thirds surface (some of them in the full surface). In 85% of cases, after 18 months of the onset of treatment, culture turned negative. After 3 months months, only five patients were completely symptom-free with negative culture. In 25 patients, only after 6 months, the absence of symptoms was achieved and the cultures negativized; in 29 patients, 9 months were required. No noticeable adverse effects were reported. This study reinforces previous works suggesting the applicability of laser therapies to treat toenail 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.

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.

Antifungal therapy for onychomycosis in children

Onychomycosis is a chronic infection of the nail unit, and its prevalence increases with age. Treatment options for children are similar to those for adults and include both oral and topical therapies. Oral agents, such as terbinafine, itraconazole, and fluconazole have been reported to have good efficacy and a low rate of side effects in children. Topical therapies, such as amorolfine and ciclopirox, can also be used as monotherapy or combined with oral agents to treat onychomycosis. Due to their thinner, faster-growing nails, children are more likely to respond to topical monotherapy than adults. There is currently insufficient data comparing emerging medical devices, such as laser therapy, with standard therapeutic options to recommend their use in children.

Potential role of tavaborole for the treatment of onychomycosis

ABSTRACT 

Systemic antifungal treatments are believed to be more effective than topicals for the treatment of onychomycosis; however, they are associated with more risks of adverse events. Tavaborole is the first member of a new class of antifungals that has been developed as a new topical nail solution for the treatment of toenail onychomycosis caused by dermatophytes. During Phase I–III clinical trials, tavaborole 5.0% nail solution showed a favorable safety and efficacy profile. Tavaborole 5.0% received US FDA market approval on 8 July 2014.