Topical drug delivery systems: a patent review

Introduction: Topical administration is the favored route for local delivery of therapeutic agents due to its convenience and affordability. The specific challenge of designing a therapeutic system is to achieve an optimal concentration of a certain drug at its site of action for an appropriate duration.

Areas covered: This review summarizes innovations from the past 3 years (2012–2015) in the field of topical drug delivery for the treatment of local infections of the vagina, nose, eye and skin. The review also throws some light on the anatomy and physiology of these organs and their various defensive barriers which affect the delivery of drugs administered topically.

Expert opinion: Topical administration has been gaining attention over the last few years. However, conventional topical drug delivery systems suffer from drawbacks such as poor retention and low bioavailability. The successful formulation of topical delivery products requires the careful manipulation of defensive barriers and selection of a soluble drug carrier. Extensive research is required to develop newer topical drug delivery systems aiming either to improve the efficacy or to reduce side effects compared to current patented systems.     

Emerging Topical Onychomycosis Therapies – Quo Vadis?

Introduction: Onychomycosis, a common chronic fungal infection affecting fingernails and toenails, globally may affect 10 – 30% of the population. This chronic disease is difficult to eradicate. The goal of developing a highly effective and safe topical treatment has not yet been reached as it depends on the type of onychomycosis and the variety of invaders.

Areas covered: Topical drug delivery to the nail is highly desirable in treating nail disorders. However, efficacy of topical therapies is low due to their limited permeability across the nail plate. Advances have especially been made by the development of new therapeutic options including new drug entities, new formulations and reformulations. This overview updates emerging topical treatments for onychomycosis, research progress and future perspectives.

Expert opinion: Development of novel effective noninvasive topical therapy for treating onychomycosis and other nail diseases such as psoriasis is long overdue. Previously there was a lack of basic knowledge about nail and its barrier properties, but with the recent increased interest in this field both from industry and academia, we hope extensive research will continue in this field to bring about successful and safe treatments for such chronic diseases.     

Topical treatment of psoriasis

Importance of the field: The majority of patients with psoriasis can be safely and effectively treated with topical therapy alone, either under the supervision of a family physician or dermatologist. For those requiring systemic agents, topical therapies can provide additional benefit. Optimal use of topical therapy requires an awareness of the range and efficacy of all products.

Areas covered in this review: The review covers the efficacy and role of topical therapies including emollients, corticosteroids, vitamin D analogs, calcineurin inhibitors, dithranol, coal tar, retinoids, keratolyics and combination therapy. The report was prepared following a PubMed and Embase literature search up to April 2010.

What the reader will gain: The paper provides a broad review of the relevant topical therapeutic options available in routine clinical practice for the management of psoriasis and a recommendation for selection of treatment.

Take home message: Topical therapies used appropriately provide a safe and effective option for the management of psoriasis. An awareness of the available products and their efficacy is key to treatment selection and patient satisfaction.     

Controlled transscleral drug delivery formulations to the eye: establishing new concepts and paradigms in ocular anti-inflammatory therapeutics and antibacterial prophylaxis

Importance of the field: The use of topical agents poses unique and challenging hurdles for drug delivery. Topical steroids effectively control ocular inflammation, but are associated with the well-recognized dilemma of patient compliance. Although administration of topical antimicrobials as prophylaxis is acceptable among ophthalmologists, this common practice has no sound evidence base. Developing a new antimicrobial agent or delivery strategy with enhanced penetration by considering the anatomical and physiological constraints exerted by the barriers of the eye is not a commonly perceived strategy. Exploiting the permeability of the sclera, subconjunctival routes may offer a promising alternative for enhanced drug delivery and tissue targeting.

Area covered in this review: Ocular drug delivery strategies were reviewed for ocular inflammation and infections clinically adopted for newer class of antimicrobials, which use a multipronged approach to limit risks of endophthalmitis.

What the reader will gain: The analysis substantiates a new transscleral drug delivery therapeutic approach for cataract surgery.

Take home message: A new anti-inflammatory and anti-infective paradigm that frees the patient from the nuisance of topical therapeutics is introduced, opening a large investigative avenue for future improved therapies.     

Advances in ocular drug delivery: emphasis on the posterior segment

Introduction: Recent advances in pharmacological therapies to treat ocular diseases such as glaucoma, age-related macular degeneration, diabetic macular edema and retinal vascular occlusions have greatly improved the prognosis for these diseases. Due to these advances in pharmacological therapy, there is a great deal of interest in minimally invasive delivery methods, which has generated rapid developments in the field of ocular drug delivery.

Areas covered: This review will summarize currently available and recent developments for ocular drug delivery to both the anterior and posterior segments. Modes of delivery, including topical, systemic, transcleral/periocular and intravitreal, will be discussed and corresponding examples will be given. This review will highlight the advantages and disadvantages of each mode of delivery and discuss strategies to address these issues.

Expert opinion: An ideal therapy should maintain effective levels of drug for the intended duration of treatment following a single application, yet a significant number of months of therapy may be required. There are numerous approaches under investigation to improve treatment options. From the use of novel biomaterial implants and depots for sustained release, to prodrug formations, to iontophoresis to improve drug delivery, the main emphasis will continue to be placed on less invasive, longer acting, sustained release formulations in the treatment of numerous ocular disorders.     

Niosomes as a propitious carrier for topical drug delivery

Introduction: Topical delivery is defined as drug targeting to the pathologic sites of skin with the least systemic absorption. Drug localization in this case is a crucial issue. For these purposes vesicular drug delivery systems including niosomes, proniosomes, liposomes and transferosomes have been developed.

Areas covered: This review first highlights the role of niosome in dermatology focusing on localized skin delivery and then reviews the most recent literatures regarding specific applications of niosomal drug delivery systems in clinics.

Expert opinion: Niosomes are becoming popular in the field of topical drug delivery due to their outstanding characteristics like enhancing the penetration of drugs, providing a sustained pattern of drug release, increasing drug stability and ability to carry both hydrophilic and lipophilic drugs.     

Microstructured bicontinuous phase formulations: their characterization and application in dermal and transdermal drug delivery

Introduction: The development of approaches to increase drug solubility and partitioning into the skin is an active area of research in topical and transdermal delivery. In addition to forming spherical aggregates, e.g., conventional oil in water or water in oil microemulsions, the combination of an oil, surfactant and water can create bicontinuous structures where the self-assembly properties of surfactants mean that the boundaries between oil and water are no longer random. This leads to the formation of specific microstructures whose intrinsic properties and interactions with the drug will determine the ability to formulate a given drug, its stability once formulated and its subsequent delivery.

Areas covered: The review explores the relationship between the microstructure of biphasic formulations, present in microemulsions and liquid crystalline phases, and drug delivery into the skin. An overview of possible internal microstructures is followed by a summary of the methods used for structure characterization. The final section presents the work to-date and discusses the efficacy of such vehicles in enhancing dermal and transdermal delivery.

Expert opinion: The combination of water, surface agent and oil generates a broad range of three dimensional structures differing in both chemical and physical proprieties. Knowledge of the microstructure is important in understanding the behavior of a formulation and its effect on drug delivery into the skin. Microstructure complexity, interactions between the drug and the vehicle (i.e., location and mobility) and those between the vehicle and the skin are key determinants of drug delivery.     

Topical drug delivery using chitosan nano- and microparticles

Introduction: Topical drug delivery offers important benefits for improving the therapeutic effect and reducing systemic side effects of the administered compounds. In addition, utilization of biopolymeric material-based systems can play a key role in developing new topical dosage forms and their applications. This review describes the advances that have been made, new strategies and as well as possible challenges of particular systems of chitosan used in topical drug delivery, including challenging innovations in topical usage of these systems that can make significant impact on clinical practice.

Areas covered: The main area covered is hypothesis that particulate carriers based on chitosan and its derivatives can penetrate the topical barriers from the body. For this reason, the novel studies described emphasize the fact that chitosan-based particular systems are popular that can be tailor-made according to in vitro and in vivo characterization. Such parameters, which are known to influence their in vivo performance, can be modulated by adjusting the formulation conditions of the chitosan-based particular systems for topical application.

Expert opinion: The topical application of drugs with particulate systems comprising a natural polymer, chitosan, is one of the most popular drug delivery routes. The aim of topical use of chitosan particles is to improve the drug bioavailability by prolonging the residence time of drugs applied topically or by enhancing the passing of drugs through the epithelial cells by opening the tight junctions between epithelial cells and also to reduce the side effects of the drugs.     

Medicated chewing gum – a potential drug delivery system

Importance of the field: Over the years, patient convenience and patient compliance-orientated research in the field of drug delivery has resulted in bringing out potential innovative drug delivery options. Out of which, medicated chewing gum (MCG) offers a highly convenient patient-compliant way of dosing medications, not only for special population groups with swallowing difficulties such as children and the elderly, but also for the general population, including the young generation.

Areas covered in this review: In this review, various formulation ingredients, different manufacturing processes, and assessment of in vivo and in vitro drug release from MCG are thoroughly discussed along with the therapeutic potential and limitations of MCG.

What the reader will gain: Readers will gain knowledge about the rationale and prominent formulation and performance evaluation strategies behind chewing gum as a drug delivery system.

Take home message: The availability of directly compressible co-processed gum material enables rapid, safe and low-cost development of MCG as a drug delivery option. By MCG formulation, revitalization of old products and reformulation of new patented products is possible, to differentiate them from upcoming generics competition in the market.     

From conventional towards new – natural surfactants in drug delivery systems design: current status and perspectives

Importance of the field: Surfactants play an important role in the development of both conventional and advanced (colloidal) drug delivery systems. There are several commercial surfactants, but a proportionally small group of them is approved as pharmaceutical excipients, recognized in various pharmacopoeias and therefore widely accepted by the pharmaceutical industry.

Areas covered in this review: The review covers some of the main categories of natural, sugar-based surfactants (alkyl polyglucosides and sugar esters) as prospective pharmaceutical excipients. It provides analysis of the physicochemical characteristics of sugar-based surfactants and their possible roles in the design of conventional or advanced drug delivery systems for different routes of administration.

What the reader will gain: Summary and analysis of recent data on functionality, applied concentrations and formulation improvements produced by alkyl polyglucosides and sugar esters in different conventional and advanced delivery systems could be of interest to researchers dealing with drug formulation.

Take home message: Recent FDA certification of an alkyl polyglucoside surfactant for topical formulation presents a significant step in the process of recognition of this relatively new group of surfactants. This could trigger further research into the potential benefits of naturally derived materials in both conventional and new drug delivery systems.     

Emerging topical treatments for psoriasis

Introduction: Psoriasis is an immune-mediated chronic inflammatory skin disease which classically presents as erythematous, scaly plaques affecting extensor surfaces of the limbs, scalp and trunk. Approximately 80% of patients have a mild-to-moderate form routinely treated with topical medications, whereas phototherapy, systemic and biological therapies are typically reserved for treatment of moderate-to-severe psoriasis.

Areas covered: The major advances in psoriasis therapy in the past 15 years have been in new immunomodulatory and biological molecules, with a significant unmet need to have new, efficient and safe topical treatment options for the large percentage of patients for whom systemic therapy is not indicated. The available topical therapies (corticosteroids and vitamin D3 analogs) have remained relatively unchanged over the past several decades. This article reviews emerging topical drugs and formulations currently under evaluation in clinical trials.

Expert opinion: The time is right for a revolution in our topical therapy armamentarium. It has lagged significantly behind the systemic biological evolution of new drug development. Our large psoriasis population with mild-to-moderate psoriasis certainly deserves potent but safe and innovative topical agents with a new mode of action as well as with long-lasting clinical efficacy.     

Nanoparticles as multifunctional devices for the topical treatment of cutaneous leishmaniasis

Introduction: Cutaneous and mucocutaneous leishmaniasis are major tropical skin diseases. Topical treatment is currently limited to the least severe forms of cutaneous leishmaniasis (CL) without risk of dissemination. It is also recommended in combination with systemic therapy for more severe forms. Progresses in this modality of treatment are hindered by the heterogeneity of the disease and shortcomings in the clinical trials.

Areas covered: This review overlooks three major modalities of topical therapies in use or under investigation against CL: chemotherapy, photodynamic therapy and immunotherapy; either with older compounds such as paramomycin or more recent nitric oxide donors, antimicrobial peptides or silver derivatives. The advantages and limitations of their administration with newer formulation strategies such as nanoparticles (NPs) are discussed.

Expert opinion: The efficacy of a topical treatment against CL depends not only on the intrinsic antileishmanial activity of the drug but also on the amount of drug available in the dermis. NPs as sustained release systems and permeation enhancers could favour the creation of a drug reservoir in the dermis. Additionally, certain NPs have immunomodulatory properties or wound healing capabilities of benefit in CL treatment. Pending task is the selective delivery of active compounds to intracellular amastigotes, because even small NPs are unable to penetrate deeply into the skin to encounter infected macrophages (except in ulcerative lesions).     

Nanocarrier-based topical drug delivery for the treatment of skin diseases

Introduction: Skin disorders will continue to cause complications in patients. At present, there is an expansion of research into dermatologic treatment due to a critical need for new treatment options to treat skin diseases.

Areas covered: The skin itself provides a natural barrier against particle penetration for topical delivery. However, it also offers a potential approach for the delivery of therapeutics, especially in diseased skin and via the openings of hair follicles. Recent innovation might be achieved in the field of dermatological treatment with improvement in the dermal localization of bioactives into the affected skin region, via novel nanocarriers that deliver the drugs directly to the target cells. After application, these nanocarriers can penetrate through the stratum corneum into viable skin and accumulate at the target site. However, noteworthy uptake does occur after damage and in certain diseased skin.

Expert opinion: Skin-targeted topical delivery by means of nanosystems, in order to produce sustained release and maintain a localized effect, will result in an effective treatment of various life-threatening dermatological conditions. In addition, research continues into the interactions between novel particles, skin and skin lipid, and the influence of particle composition on drug distribution within the skin strata.     

Vaginal drug delivery: strategies and concerns in polymeric nanoparticle development

Introduction: Vaginal infection is widespread and > 80% of females encounter such infections during their lives. Topical treatment and prevention of vaginal infection allows direct therapeutic action, reduced drug doses and adverse effects, convenient administration and improved compliance. The advent of nanotechnology results in the use of nanoparticulate vehicle to control drug release, to enhance dosage form mucoadhesive properties and vaginal retention, and to promote mucus and epithelium permeation for both extracellular and intracellular drug delivery.

Areas covered: This review discusses the conflicting formulation requirements on polymeric nanoparticles in order to have them mucoadhesive and retentive in vaginal tract, while able to penetrate through mucus to reach adherent mucus layer or epithelium surfaces to prolong extracellular drug release, or facilitate mucosal permeation and intracellular drug delivery.

Expert opinion: Nanoscale systems are potentially useful in topical vaginal drug delivery. A thorough understanding of their mucus penetration and retention behavior as a function of their formulation, size and surface properties, biorecognition, pH, temperature or other stimuli responsiveness is essential for design of therapeutically effective nanomatrices.     

Safety considerations with combination therapies for psoriasis

ABSTRACT

Introduction: Psoriasis is a chronic inflammatory skin disease that waxes and wanes, and long-term remission can be difficult to achieve regardless of disease severity. Currently, numerous treatment options are available for psoriasis including steroid and non-steroid topical agents, phototherapy, oral systemic agents, and biologics, with many more therapeutic agents under development.

Areas covered: This article will review various combination therapy strategies such as rotational therapy and sequential therapy and describe a variety of safe and effective combination therapies for the treatment of psoriasis. Two or more agents with different mechanisms of action and safety profiles can be used to achieve and/or maintain adequate disease control while minimizing the toxicity of treatments. Combination therapy can also be used when a single agent is not enough for treating recalcitrant disease. Choosing a combination regimen that maximizes safety and efficacy while considering patient usability and compliance can be a challenge.

Expert opinion: Given the various treatment options currently available for psoriasis and more agents under development, combination therapy will continue to be a valuable treatment strategy for any patient with psoriasis. It is crucial for clinicians to carefully consider the fine balance between safety and efficacy when combining various therapeutic agents.     

Dermal delivery of doxorubicin-loaded solid lipid nanoparticles for the treatment of skin cancer

Objective: Dermal delivery of Doxorubicin (Dox) would be an ideal way in maximising drug efficiency against skin cancer accompanying with minimising side effects. We investigated the potential of Dox-loaded Solid lipid nanoparticles (SLNs) for topical delivery against skin cancer.

Methods: In vitro and in vivo cytotoxicity of optimised formulation were evaluated on murine melanoma (B16F10) cells by MTT assay and melanoma induced Balb/C mice, respectively. Animal study followed by histological analysis.

Results: Optimised formulation showed mean particle size and encapsulation efficiency (EE) of 92?nm and 86% w/w (0.86% w/w value of encapsulated Dox in the lipid matrix), respectively. FTIR experiment confirmed drug–lipid interaction interpreting the observed high EE value for Dox. In vitro and in vivo results indicated the superiority of cytotoxic performance of Dox-loaded SLN compared to Dox solution.

Conclusion: Our findings may open the possibilities for the topical delivery of Dox to the skin cancerous tissues.     

Insights into drug delivery across the nail plate barrier

Abstract

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.     

Nanoparticle-based vaginal drug delivery systems for HIV prevention

Importance of the Field: Several strategies are being investigated for the prevention of heterosexual transmission of HIV. Of these, topical vaginal drug delivery systems, microbicides, are being actively pursued. HIV prevention by means of a topical microbicide has several drug delivery challenges. These challenges include the vaginal mucosal barriers and potential degradation of the drugs in the vaginal lumen due to pH and enzymes present. Also, new drugs being evaluated as microbicides have specific mechanisms of action, which in some cases require drug targeting to a specific site of action. Nanoparticles provide a delivery strategy for targeted or controlled delivery to the vagina which can be applied in the field of HIV prevention.

Areas covered in the review: This review summarizes nanoparticulate systems and their use in mucosal delivery to date. The sexual transmission of HIV along with the various targets to prevent transmission are discussed as well as the potential opportunities, challenges and advantages in using a nanoparticle-based approach for microbicidal drug delivery.

What the reader will gain: This review provides a general understanding of vaginal drug delivery, its challenges, and nanoparticulate delivery systems. Additionally, insight will be gained as to the limited existing application of this technology to the field of HIV prevention.

Take home message: To date, few studies have been published that exploit nanoparticle-based microbicidal delivery to the vagina. The use of nanoparticles for vaginal drug delivery provides an approach to overcome the existing barriers to success.     

Low-frequency sonophoresis: application to the transdermal delivery of macromolecules and hydrophilic drugs

Importance of the field: Transdermal delivery of macromolecules provides an attractive alternative route of drug administration when compared to oral delivery and hypodermic injection because of its ability to bypass the harsh gastrointestinal tract and deliver therapeutics non-invasively. However, the barrier properties of the skin only allow small, hydrophobic permeants to traverse the skin passively, greatly limiting the number of molecules that can be delivered via this route. The use of low-frequency ultrasound for the transdermal delivery of drugs, referred to as low-frequency sonophoresis (LFS), has been shown to increase skin permeability to a wide range of therapeutic compounds, including both hydrophilic molecules and macromolecules. Recent research has demonstrated the feasibility of delivering proteins, hormones, vaccines, liposomes and other nanoparticles through LFS-treated skin. In vivo studies have also established that LFS can act as a physical immunization adjuvant. LFS technology is already clinically available for use with topical anesthetics, with other technologies currently under investigation.

Areas covered in this review: This review provides an overview of mechanisms associated with LFS-mediated transdermal delivery, followed by an in-depth discussion of the current applications of LFS technology for the delivery of hydrophilic drugs and macromolecules, including its use in clinical applications.

What the reader will gain: The reader will gain an insight into the field of LFS-mediated transdermal drug delivery, including how the use of this technology can improve on more traditional drug delivery methods.

Take home message: Ultrasound technology has the potential to impact many more transdermal delivery platforms in the future due to its unique ability to enhance skin permeability in a controlled manner.     

Current aspects of formulation efforts and pore lifetime related to microneedle treatment of skin

Importance of the field: The efficacy of microneedles in the area of transdermal drug delivery is well documented. Multiple studies have shown that enhancement of skin permeation by means of the creation of microscopic pores in the stratum corneum can greatly improve the delivery rates of drugs. However, skin pretreatment with microneedles is not the only factor affecting drug transport rates. Other factors, including drug formulation and rate of micropore closure, are also important for optimizing delivery by this route.

Areas covered in this review: This review aims to highlight work that has been done in these areas, with an emphasis on drug formulation parameters that affect transdermal flux.

What the reader will gain: This review creates an appreciation for the many factors affecting microneedle-enhanced delivery. Most results clearly indicate that microneedle skin pretreatment by itself may have different effects on drug transport depending on the formulation used, and formulation characteristics have different effects on the transport through untreated skin and microneedle-treated skin. Several formulation approaches are reported to optimize microneedle-enhanced drug delivery, including co-solvent use, vesicular, nanoparticulate and gel systems.

Take home message: In addition to well-established factors that affect microneedle-assisted delivery (geometry, type of microneedle, etc.), formulation and pore viability are also critical factors that must be considered.