Novel NSAIDs ophthalmic formulation: flurbiprofen axetil emulsion with low irritancy and improved anti-inflammation effect

Etiopathology, Epidemiology, Diagnosis, and Treatment of Fungal Keratitis

Fungal keratitis (FK) is a severe ocular condition resulting from corneal infection that is prevalent in tropical countries, particularly in developing regions of Asia and Africa. Factors like corneal lens misuse, inappropriate steroid use, and diagnostic challenges have provoked the epidemic. FK causes significant vision impairment, scarring, and ocular deformities. Accurate pathological diagnosis is crucial for effective therapeutic intervention. Topical antifungal therapy with surface healing medications proves effective in preventing fungal-borne ulcers. Managing FK requires a comprehensive understanding of fungal pathogenesis, guiding formulation strategies and preventive measures to curb global ocular blindness. This review provides in-depth insights into FK, covering etiology, epidemiology, pathogenesis, therapeutic interventions, antifungal resistance, limitations, prevention, and future perspectives on ocular surface disease management.

Advancing ophthalmic delivery of flurbiprofen via synergistic chiral resolution and ion-pairing strategies

Flurbiprofen (FB), a nonsteroidal anti-inflammatory drug, is widely employed in treating ocular inflammation owing to its remarkable anti-inflammatory effects. However, the racemic nature of its commercially available formulation (Ocufen®) limits the full potential of its therapeutic activity, as the (S)-enantiomer is responsible for the desired anti-inflammatory effects. Additionally, the limited corneal permeability of FB significantly restricts its bioavailability. In this study, we successfully separated the chiral isomers of FB to obtain the highly active (S)-FB. Subsequently, utilizing ion-pairing technology, we coupled (S)-FB with various counter-ions, such as sodium, diethylamine, trimethamine (TMA), and l-arginine, to enhance its ocular bioavailability. A comprehensive evaluation encompassed balanced solubility, octanol-water partition coefficient, corneal permeability, ocular pharmacokinetics, tissue distribution, and in vivo ocular anti-inflammatory activity of each chiral isomer salt. Among the various formulations, S-FBTMA exhibited superior water solubility (about 1-12 mg/ml), lipid solubility (1< lg Pow < 3) and corneal permeability. In comparison to Ocufen®, S-FBTMA demonstrated significantly higher in vivo anti-inflammatory activity and lower ocular irritability (such as conjunctival congestion and tingling). The findings from this research highlight the potential of chiral separation and ion-pair enhanced permeation techniques in providing pharmaceutical enterprises focused on drug development with a valuable avenue for improving therapeutic outcomes.

γ-Cyclodextrin-based polypseudorotaxane hydrogels for ophthalmic delivery of flurbiprofen to treat anterior uveitis

Anterior uveitis is a sight-threatening inflammation inside the eyes. Conventional eye drops for anti-inflammatory therapy need to be administered frequently owing to the rapid elimination and corneal barrier. To address these issues, polypseudorotaxane hydrogels were developed by mixing Soluplus micelles (99.4 nm) and cyclodextrins solution. The optimized hydrogels exhibited shear-thinning and sustained release properties. The hydrogels exhibited higher transcorneal permeability coefficient (P_app, 1.84 folds) than that of drug solutions. Moreover, animal study indicated that the hydrogels significantly increased the precorneal retention (AUC, 21.2 folds) and intraocular bioavailability of flurbiprofen (AUC_{Aqueous humor}, 17.8 folds) in comparison with drug solutions. Importantly, the hydrogels obviously boosted anti-inflammatory efficacy in rabbit model of endotoxin-induced uveitis at a reduced administration frequency. Additionally, the safety of hydrogels was confirmed by cytotoxicity and ocular irritation studies. In all, the present study demonstrates a friendly non-invasive strategy based on γ-CD-based polypseudorotaxane hydrogels for ocular drug delivery.

Drug Delivery Challenges and Current Progress in Nanocarrier-Based Ocular Therapeutic System

Drug instillation via a topical route is preferred since it is desirable and convenient due to the noninvasive and easy drug access to different segments of the eye for the treatment of ocular ailments. The low dose, rapid onset of action, low or no toxicity to the local tissues, and constrained systemic outreach are more prevalent in this route. The majority of ophthalmic preparations in the market are available as conventional eye drops, which rendered <5% of a drug instilled in the eye. The poor drug availability in ocular tissue may be attributed to the physiological barriers associated with the cornea, conjunctiva, lachrymal drainage, tear turnover, blood–retinal barrier, enzymatic drug degradation, and reflex action, thus impeding deeper drug penetration in the ocular cavity, including the posterior segment. The static barriers in the eye are composed of the sclera, cornea, retina, and blood–retinal barrier, whereas the dynamic barriers, referred to as the conjunctival and choroidal blood flow, tear dilution, and lymphatic clearance, critically impact the bioavailability of drugs. To circumvent such barriers, the rational design of the ocular therapeutic system indeed required enriching the drug holding time and the deeper permeation of the drug, which overall improve the bioavailability of the drug in the ocular tissue. This review provides a brief insight into the structural components of the eye as well as the therapeutic challenges and current developments in the arena of the ocular therapeutic system, based on novel drug delivery systems such as nanomicelles, nanoparticles (NPs), nanosuspensions, liposomes, in situ gel, dendrimers, contact lenses, implants, and microneedles. These nanotechnology platforms generously evolved to overwhelm the troubles associated with the physiological barriers in the ocular route. The controlled-drug-formulation-based strategic approach has considerable potential to enrich drug concentration in a specific area of the eye.

Development of lipid-based microsuspensions for improved ophthalmic delivery of gentamicin sulphate

Aim: Anterior eye segment disorders are treated with eye drops and ointments, which have low ocular bioavailability necessitating the need for improved alternatives. Lipid microsuspension of gentamicin sulphate was developed for the treatment of susceptible eye diseases. Materials & methods: Lipid microsuspensions encapsulating gentamicin sulphate were produced by hot homogenization and evaluated. Ex vivo permeation and ocular irritancy tests were also conducted. Results & conclusion: Stable microsuspensions with high entrapment efficiency and satisfactory osmolarities were obtained. Release studies achieved 49-88% in vitro release at 12 h with sustained permeability of gentamicin compared with conventional gentamicin eye drop (Evril^®). No irritation was observed following Draize's test. The microsuspensions have great potential as ocular delivery system of gentamicin sulphate.

Nanotechnology for the Treatment of Allergic Conjunctival Diseases

Allergic conjunctivitis is one of the most common external eye diseases and the prevalence has been increasing. The mainstay of treatment is topical eye drops. However, low bioavailability, low ocular drug penetration, transient resident time on the ocular surface due to tear turnover, frequent topical applications and dependence on patient compliance, are the main drawbacks associated with topical administration. Nanotechnology-based medicine has emerged to circumvent these limitations, by encapsulating the drugs and preventing them from degradation and therefore providing sustained and controlled release. Using a nanotechnology-based approach to load the drug is particularly useful for the delivery of hydrophobic drugs such as immunomodulatory agents, which are commonly used in allergic conjunctival diseases. In this review, different nanotechnology-based drug delivery systems, including nanoemulsions, liposomes, nanomicelles, nanosuspension, polymeric and lipid nanoparticles, and their potential ophthalmic applications, as well as advantages and disadvantages, are discussed. We also summarize the results of present studies on the loading of immunomodulators or nonsteroidal anti-inflammatory drugs to nano-scaled drug delivery systems. For future potential clinical use, research should focus on the optimization of drug delivery designs that provide adequate and effective doses with safe and satisfactory pharmacokinetic and pharmaco-toxic profiles.

Preparation and Evaluation of Cubosomes/Cubosomal Gels for Ocular Delivery of Beclomethasone Dipropionate for Management of Uveitis

PURPOSE

Topical corticosteroids administration is commonly used for management of various ocular conditions especially those affecting the anterior segment of the eye. Poor solubility and limited pre-corneal residence time result in insufficient drug penetration to the outer (cornea and conjunctival-scleral) coats of the eye. This study aimed to prepare and evaluate cubosomes for prolonging residence time and enhancing ocular bioavailability of BDP.

METHODS

GMO-cubosomes were prepared using the top-down technique. Two stabilizers were investigated: poloxamer 407 and solulan C24. Particle size, EE %, polarized-light microscopy, TEM, in vitro release, transcorneal permeation, BCOP, histopathology and in vivo evaluation for treatment of uveitis in a rabbits' model were studied.

RESULTS

The prepared cubosomes were of nano-sizes (100 nm - 278 nm); EE% was around 94%. The cubosomes were confirmed by visualizing the "Maltese crosses" textures. Transcorneal permeation was significantly (p < 0.05) improved, compared to BDP-suspension (the control formulation). The optimized cubosomes F1P was incorporated in CMC gel (Cubo-gel). The prepared Cubo-gel formulations showed better rheological characteristics and high ocular tolerability. Superior anti-inflammatory properties were recorded for the Cubo-gel for treatment of endotoxin-induced uveitis in the rabbit model when compared to the control BDP-suspension.

CONCLUSIONS

Transcorneal permeation parameters P_app and flux and AUC_0-10h markedly enhanced by up to 4-, 5.8-and 5.5-fold respectively, compared to the control BDP-suspension formulation. This study suggested that cubosomes/Cubo-gel could be an auspicious ocular delivery system for BDP that was able to effectively treat uveitis (a disease of the posterior segment of the eye).

Recent Advances in the Design of Topical Ophthalmic Delivery Systems in the Treatment of Ocular Surface Inflammation and Their Biopharmaceutical Evaluation

Ocular inflammation is one of the most common symptom of eye disorders and diseases. The therapeutic management of this inflammation must be rapid and effective in order to avoid deleterious effects for the eye and the vision. Steroidal (SAID) and non-steroidal (NSAID) anti-inflammatory drugs and immunosuppressive agents have been shown to be effective in treating inflammation of the ocular surface of the eye by topical administration. However, it is well established that the anatomical and physiological ocular barriers are limiting factors for drug penetration. In addition, such drugs are generally characterized by a very low aqueous solubility, resulting in low bioavailability as only 1% to 5% of the applied drug permeates the cornea. The present review gives an updated insight on the conventional formulations used in the treatment of ocular inflammation, i.e., ointments, eye drops, solutions, suspensions, gels, and emulsions, based on the commercial products available on the US, European, and French markets. Additionally, sophisticated formulations and innovative ocular drug delivery systems will be discussed. Promising results are presented with micro- and nanoparticulated systems, or combined strategies with polymers and colloidal systems, which offer a synergy in bioavailability and sustained release. Finally, different tools allowing the physical characterization of all these delivery systems, as well as in vitro, ex vivo, and in vivo evaluations, will be considered with regards to the safety, the tolerance, and the efficiency of the drug products.

Advanced Formulation Approaches for Ocular Drug Delivery: State-Of-The-Art and Recent Patents

The eye presents extensive perspectives and challenges for drug delivery, mainly because of the extraordinary capacity, intrinsic to this path, for drugs to permeate into the main circulatory system and also for the restrictions of the ocular barriers. Depending on the target segment of the eye, anterior or posterior, the specifications are different. The ocular route experienced in the last decades a lot of progresses related with the development of new drugs, improved formulations, specific-designed delivery and even new routes to administer a drug. Concomitantly, new categories of materials were developed and adapted to encapsulate drugs. With such advances, a multiplicity of parameters became possible to be optimized as the increase in bioavailability and decreased toxic effects of medicines. Also, the formulations were capable to easily adhere to specific tissues, increase the duration of the therapeutic effect and even target the delivery of the treatment. The ascending of new delivery systems for ocular targeting is a current focus, mainly because of the capacity to extend the normal time during which the drug exerts its therapeutic effect and, so, supplying the patients with a product which gives them fewer side effects, fewer number of applications and even more effective outcomes to their pathologies, surpassing the traditionally-used eye drops. Depending on the systems, some are capable of increasing the duration of the drug action as gels, emulsions, prodrugs, liposomes, and ocular inserts with hydrophilic properties, improving the absorption by the cornea. In parallel, other devices use as a strategy the capacity to sustain the release of the carried drugs by means of erodible and non-erodible matrices. This review discusses the different types of advanced formulations used for ocular delivery of therapeutics presenting the most recent patents according to the clinical applications.

Ocular Drug Delivery

Although the eye is an accessible organ for direct drug application, ocular drug delivery remains a major challenge due to multiple barriers within the eye. Key barriers include static barriers imposed by the cornea, conjunctiva, and retinal pigment epithelium and dynamic barriers including tear turnover and blood and lymphatic clearance mechanisms. Systemic administration by oral and parenteral routes is limited by static blood-tissue barriers that include epithelial and endothelial layers, in addition to rapid vascular clearance mechanisms. Together, the static and dynamic barriers limit the rate and extent of drug delivery to the eye. Thus, there is an ongoing need to identify novel delivery systems and approaches to enhance and sustain ocular drug delivery. This chapter summarizes current and recent experimental approaches for drug delivery to the anterior and posterior segments of the eye.

Nanomicelle-Assisted Targeted Ocular Delivery with Enhanced Antiinflammatory Efficacy In Vivo

Ocular inflammations are common diseases that may lead to serious vision-threatening obstacles. Eye drops for antiinflammation therapy need to be administered multiple times daily at a high dosage due to the rapid precorneal removal and low bioavailability of drugs. To overcome these problems, a cRGD-functionalized DSPE-PEG2000 nanomicelle (DSPE-PEG2000-cRGD) encapsulated with flurbiprofen is proposed. The tailored nanomicelles trigger specific binding to integrin receptors on the ocular surface, which leads to rapid and robust mucoadhesion, superior ocular surface retention, and transcorneal penetration behaviors of nanomicelles. Due to the enhanced drug delivery on ocular surface and in aqueous humor, the functionalized nanoformulation significantly improves ocular antiinflammation efficacy at a low dosage by blocking the synthesis of inflammatory mediators and cytokines. The present study demonstrates a promising strategy that uses a functional peptide combined with nanomicelles for targeted delivery to the eye in ophthalmologic applications.

Non-invasive strategies for targeting the posterior segment of eye

The safe and effective treatment of eye diseases has been remained a global myth. Several advancements have been done and various drug delivery and treatment techniques have been suggested. The Posterior segment disorders are the leading cause of visual impairments and blindness. Targeting the therapeutic agents to the anterior and posterior segments of the eye has attracted extensive attention from the scientific community. Significant key factors in the success of ocular therapy are the development of safe, effective, economic and non-invasive novel drug delivery systems. These specialized non-invasive ocular drug delivery systems revolutionized the drug delivery strategies by overcoming the limitations, provided targeted delivery to the ocular tissues by avoiding larger doses, and reducing the toxicity encountered by the conventional approaches. These non-invasive systems are fabricated by ingredients encompassing biodegradability, biocompatibility, mucoadhesion, solubility and permeability enhancement and stimuli responsiveness. The variety of routes are utilized to provide minimally invasive drug delivery to the patients without any discomfort and pain. This review is focused on the brief introduction, types, significance, preparation techniques, components and mechanism of drug release of non-invasive systems, including in situ gelling systems, microspheres, iontophoresis, nanoparticles, nanosuspensions and specialized novel emulsions.

Nanostructure-based platforms-current prospective in ophthalmic drug delivery

The topically applied drugs as drops are washed off from the eye in very short period, resulting in low ocular bioavailability of drugs. Number of approaches have been attempted to increase the bioavailability and the duration of action of ocular drugs. This review provides an insight into various novel approaches; hydrophilic nanogels, solid lipid nanoparticles, and nanosponges applied very recently in the delivery of insoluble drugs, prolonging the ocular residence time, minimize pre-corneal drug loss and, therefore, bioavailability and therapeutic efficacy of the drugs. Despite various scientific approaches, efficient ocular drug delivery remains a challenge for pharmaceutical scientists.

A facile approach for the fabrication of nano-attapulgite/poly(vinyl pyrrolidone)/biopolymers core–sheath ultrafine fibrous mats for drug controlled release

Herein, we report a facile method for the fabrication of flurbiprofen axetil (FA)-loaded core–sheath composite ultrafine fibers for drug sustained release.

Hydrophobically-modified poly(vinyl pyrrolidone) as a physically-associative, shear-responsive ophthalmic hydrogel

The potential of hydrophobically-modified poly(vinyl pyrrolidone) as a shear-responsive, self-associative hydrogel for ophthalmic applications is demonstrated. Hydrophobic modification was achieved via random copolymerization of N-vinylpyrrolidone with N-vinylformamide, the latter of which can be hydrolyzed to expose a desired degree of reactive amine groups permitting grafting of alkyl chlorides of varying alkyl chain lengths. The resulting materials formed highly shear-responsive physical hydrogels, exhibiting tunable shear thinning over 4-5 decades of viscosity from infinite shear to zero shear conditions that facilitates lubrication upon blinking and/or facile injection or drop-based delivery to the anterior or posterior segments of the eye. Viscosity changes due to self-association over time can also be tuned by changing the length of the hydrophobe, with C18-grafted materials exhibiting prolonged thickening over several weeks to form extremely stiff hydrogels and shorter grafts equilibrating significantly faster but forming weaker gels. The hydrogels remained transparent even at very high polymer concentrations (20 wt%) and are demonstrated to facilitate controlled release of a model drug (doxorubicin). The polymers exhibit minimal cytotoxicity in vitro to human corneal epithelial cells and retinal pigment epithelial cells, particularly when lower molecular weight backbone polymers were used. In vivo assessments in rabbits indicated no significant conjunctival edema or redness, secretion, corneal opacity, or iris involvement upon anterior application. Following intravitreal injection in rat eyes, no opacification of the lens, cornea or vitreous, nor any morphological or functional change to the posterior segment was observed. Examination of wholemount tissues and histology demonstrated no adverse effect from the injection or deposition of material. As such, these shear-thinning materials offer potential for drug delivery in both the anterior and posterior segments or as a vitreal replacement that can be easily administered or removed.

Nanotherapies for the treatment of ocular diseases

The topical route is the most frequent and preferred way to deliver drugs to the eye. Unfortunately, the very low ocular drug bioavailability (less than 5%) associated with this modality of administration, makes the efficient treatment of several ocular diseases a significant challenge. In the last decades, it has been shown that specific nanocarriers can interact with the ocular mucosa, thereby increasing the retention time of the associated drug onto the eye, as well as its permeability across the corneal and conjunctival epithelium. In this review, we comparatively analyze the mechanism of action and specific potential of the most studied nano-drug delivery carriers. In addition, we present the success achieved until now using a number of nanotherapies for the treatment of the most prevalent ocular pathologies, such as infections, inflammation, dry eye, glaucoma, and retinopathies.

Synthesis and characterization of flurbiprofen axetil-loaded electrospun MgAl-LDHs/poly(lactic-co-glycolic acid) composite nanofibers

A model drug FA was intercalated into the interlayers of layered double hydroxides (LDHs) and the particles were dispersed into the PLGA nanofibers to form a carrier for drug sustained release.

Development of a novel solid lipid nanoparticles-loaded dual-reverse thermosensitive nanomicelle for intramuscular administration with sustained release and reduced toxicity

The DRTN was prepared with flurbiprofen-loaded SLNs, poloxamers and water. The suspension transformed into a hydrogel at body temperature. The rheological characterization, release, pharmacokinetics and morphology were evaluated.

Ophthalmic drug dosage forms: characterisation and research methods

This paper describes hitherto developed drug forms for topical ocular administration, that is, eye drops, ointments, in situ gels, inserts, multicompartment drug delivery systems, and ophthalmic drug forms with bioadhesive properties. Heretofore, many studies have demonstrated that new and more complex ophthalmic drug forms exhibit advantage over traditional ones and are able to increase the bioavailability of the active substance by, among others, reducing the susceptibility of drug forms to defense mechanisms of the human eye, extending contact time of drug with the cornea, increasing the penetration through the complex anatomical structure of the eye, and providing controlled release of drugs into the eye tissues, which allows reducing the drug application frequency. The rest of the paper describes recommended in vitro and in vivo studies to be performed for various ophthalmic drugs forms in order to assess whether the form is acceptable from the perspective of desired properties and patient's compliance.

Ocular drug delivery systems: An overview

The major challenge faced by today’s pharmacologist and formulation scientist is ocular drug delivery. Topical eye drop is the most convenient and patient compliant route of drug administration, especially for the treatment of anterior segment diseases. Delivery of drugs to the targeted ocular tissues is restricted by various precorneal, dynamic and static ocular barriers. Also, therapeutic drug levels are not maintained for longer duration in target tissues. In the past two decades, ocular drug delivery research acceleratedly advanced towards developing a novel, safe and patient compliant formulation and drug delivery devices/techniques, which may surpass these barriers and maintain drug levels in tissues. Anterior segment drug delivery advances are witnessed by modulation of conventional topical solutions with permeation and viscosity enhancers. Also, it includes development of conventional topical formulations such as suspensions, emulsions and ointments. Various nanoformulations have also been introduced for anterior segment ocular drug delivery. On the other hand, for posterior ocular delivery, research has been immensely focused towards development of drug releasing devices and nanoformulations for treating chronic vitreo-retinal diseases. These novel devices and/or formulations may help to surpass ocular barriers and associated side effects with conventional topical drops. Also, these novel devices and/or formulations are easy to formulate, no/negligibly irritating, possess high precorneal residence time, sustain the drug release, and enhance ocular bioavailability of therapeutics. An update of current research advancement in ocular drug delivery necessitates and helps drug delivery scientists to modulate their think process and develop novel and safe drug delivery strategies. Current review intends to summarize the existing conventional formulations for ocular delivery and their advancements followed by current nanotechnology based formulation developments. Also, recent developments with other ocular drug delivery strategies employing in situ gels, implants, contact lens and microneedles have been discussed.

Novel strategies for anterior segment ocular drug delivery

Research advancements in pharmaceutical sciences have led to the development of new strategies in drug delivery to anterior segment. Designing a new delivery system that can efficiently target the diseased anterior ocular tissue, generate high drug levels, and maintain prolonged and effective concentrations with no or minimal side effects is the major focus of current research. Drug delivery by traditional method of administration via topical dosing is impeded by ocular static and dynamic barriers. Various products have been introduced into the market that prolong drug retention in the precorneal pocket and to improve bioavailability. However, there is a need of a delivery system that can provide controlled release to treat chronic ocular diseases with a reduced dosing frequency without causing any visual disturbances. This review provides an overview of anterior ocular barriers along with strategies to overcome these ocular barriers and deliver therapeutic agents to the affected anterior ocular tissue with a special emphasis on nanotechnology-based drug delivery approaches.

Recent advances in topical ophthalmic drug delivery with lipid-based nanocarriers

Ocular barriers and the poor water solubility of drug candidates present a number of problems for the development of ocular drug delivery systems. Recently, the emergence of lipid-based nanocarriers has provided a viable means of enhancing the bioavailability of ophthalmic formulations. A number of these formulations have been found to be clinically active and several others are currently undergoing clinical trials. In this review, the advantages of lipid-based nanocarriers as non-invasive topical ocular drug delivery systems are presented. Many systems, including emulsions, liposomes, cubosomes, niosomes and other lipid-based nanocarriers, are reviewed.