Non-aqueous formulations in topical ocular drug delivery - a paradigm shift?

Cyclosporine a Eluting Nano Drug Reservoir Film for the Management of Dry Eye Disease

Cyclosporine A (CsA) is widely used to treat dry eye disease (DED), and ocular morbidity is on the rise and is a growing concern globally. However, several drug and formulation challenges, such as poor drug solubility, short pre-corneal residence time, and poor patient compliance, have limited the ocular bioavailability of CsA to < 5%. A CsA cyclodextrin-based ternary complex loaded dissolvable nano drug reservoir films were developed to overcome these limitations and efficiently manage DED. Drug-loaded nano-reservoir films were fabricated via lithography using silicone and poly (dimethyl siloxane) (PDMS) molds. Different physicochemical characterizations were performed to confirm the formation of stable CsA-cyclodextrin-based ternary complexes. Formation of nanoreservoirs on the films was confirmed using SEM and AFM. Optimized CsA-complex-loaded nano-reservoir films were evaluated for in vitro drug release, ex vivo corneal permeation, and in vivo precorneal retention. Preclinical efficacy studies were performed to assess the efficacy of CsA-complex-loaded nano-reservoirs in an experimental dry-eye mouse model. Physicochemical characterization confirmed the formation of a stable complex and the improved solubility of CsA. In vitro release and ex vivo permeation studies indicated a controlled drug release and improved permeation, respectively. Furthermore, tear volume measurement and corneal damage assessment using slit-lamp imaging suggested decreased dry eye symptoms, significantly increasing tear volume in the drug-loaded nano-reservoir-treated group. Moreover, histopathological studies corroborated the tear volume and slit-lamp imaging results, with reduced inflammation and neovascularization. The poorly water-soluble drug with cyclodextrin complex incorporated nanoreservoir films presents a potential alternative for managing various ocular diseases.

Quercetin loaded biogenic squalene nano-lipid carriers for the treatment of dry eye syndrome

In this study, quercetin-incorporated squalene nanostructured lipid carriers (QS-NLCs) were developed to mitigate the pathological conditions of dry eye disease (DED). The melt emulsification method was used to prepare QS-NLCs. The resulting NLCs have 93.74 ± 9.32 nm particle size, 43.8 ± 5.42 % drug loading and showed good stability for 90 days at different storage conditions. The structural characterization of NLCs was carried out through DSC, FTIR, and XRD, and the morphological study was conducted using TEM analysis. The morphological study emphasised no agglomeration was present in the formulation, and further -31.47 ± 2.18 mV zeta potential supported the TEM analysis. Also, the QS-NLCs showed a release pattern in which more than 70 % of the drug was released in the medium in 1 h. After that, a sustained release pattern was observed for 6 h. However, QS-NLCs also showed higher ex-vivo corneal permeation, i.e., ∼2.5-fold, as compared to free quercetin. Also, no significant difference was observed in the moisture retention capacity of NLCs when compared with control glycerin. Further, the QS-NLCs showed good anti-inflammatory and cytotoxicity activities against RAW 264.7 and HCECs cell lines, respectively. Furthermore, 18.22 ± 1.23 mm of Schirmer score in a 5-day tear production study and a 2.79-fold increased half-life (T1/2), 3.02-fold enhanced area under the curve (AUC0-∞), and 2.88-fold higher mean retention time (MRT0-∞) were obtained which signified the higher bioavailability of QS-NLCs with higher ocular tolerance ensured by modified Draize test. Most importantly, the proposed QS-NLCs improved the pharmacological activities of quercetin against DED.

Bringing ophthalmology into the scientific world: Novel nanoparticle-based strategies for ocular drug delivery

The distinctive benefits and drawbacks of various drug delivery strategies to supply corneal tissue improvement for sense organs have been the attention of studies worldwide in recent decades. Static and dynamic barriers of ocular tissue prevent foreign chemicals from entering and inhibit the active absorption of therapeutic medicines. The distribution of different medications to ocular tissue is one of the most appealing and demanding tasks for investigators in pharmacology, biomaterials, and ophthalmology, and it is critical for cornea wound healing due to the controlled release rate and increased drug bioavailability. It should be mentioned that the transport of various types of medications into the different sections of the eye, particularly the cornea, is exceedingly challenging because of its distinctive structure and various barriers throughout the eye. Nanoparticles are being studied to improve medicine delivery strategies for ocular disease. Repetitive corneal drug delivery using biodegradable nanocarriers allows a medicine to remain in different parts of the cornea for extended periods of time and thus improve administration route effectiveness. In this review, we discussed eye anatomy, ocular delivery barriers, as well as the emphasis on the biodegradable nanomaterials ranging from organic nanostructures, such as nanomicelles, polymers, liposomes, niosomes, nanowafers, nanoemulsions, nanosuspensions, nanocrystals, cubosomes, olaminosomes, hybridized NPs, dendrimers, bilosomes, solid lipid NPs, nanostructured lipid carriers, and nanofiber to organic nanomaterials like silver, gold, and mesoporous silica nanoparticles. In addition, we describe the nanotechnology-based ophthalmic medications that are presently on the market or in clinical studies. Finally, drawing on current trends and therapeutic approaches, we discuss the challenges that innovative optical drug delivery systems confront and propose future research routes. We hope that this review will serve as a source of motivation and inspiration for developing innovative ophthalmic formulations.

Preparation of dried nanoemulsion formulation by electrospinning

Dry eye disease is a multifactorial condition characterized by a loss of homeostasis of the tear film. Among the various treatment approaches, the application of ophthalmic oil-in-water nanoemulsions with incorporated anti-inflammatory drugs represents one of the most advanced approaches. However, the liquid nature of nanoemulsions limits their retention time at the ocular surface. Transforming the nanoemulsions into a dry form that would disperse rapidly in the tear fluid would improve the retention of the drug at the ocular surface. The aim of this study was to investigate electrospinning as a method for the preparation of a solid eye preparation based on nanoemulsion loaded with the anti-inflammatory drug loteprednol etabonate. Four nanoemulsions differing in oil-to-surfactant ratios were incorporated in hydrophilic nanofibers based on polyethylene oxide, poloxamer 188, and Soluplus®. The dried nanoemulsions in the form of nanofibers dispersed readily on contact with aqueous medium, resulting in a dispersion of nanometre-sized droplets with average size comparable to the average droplet size of the initial nanoemulsions. A rheological study revealed the predominant elastic behavior of the dispersed nanofibers, which indicates the formation of a weak gel after the dispersion of the dried nanoemulsion in tear fluid at the ocular surface. The biocompatibility of the dried nanoemulsions in the form of nanofibers after a single and multiple-dose application was confirmed using the 3D HCE-T model of the stratified epithelium of the human cornea, suggesting that this innovative solid eye preparation could represent a new approach to the treatment of dry eye disease.

A systematic review of improper eye drop application and role of pharmacists for patient education

The application of eye drop is encountered with many technique errors, which can lead to decreased therapeutic response and treatment failure. Community pharmacists can play a pivotal role in providing appropriate knowledge and counselling services for the proper and effective use of eye drop. The aim of this systematic review was to assess the most important aspects of technique errors regarding eye drop application, along with the important role and impact of community pharmacist-led interventions towards the provision of patient education and counselling regarding the proper application of this topical preparation in clinical practice. PRISMA criteria were used to conduct a systematic search on the administration of eye drop through different databases, including Scopus, Web of Science, and PubMed between the years 1990 and 2023. A total of 22 articles were included in this study. Nearly three-quarters of the studies discussed the improper technique and non-adherence for eye drop instillation (77.3%). Five studies discussed the interventions by health care professionals for proper eye drop instillation technique (22.7%). Two studies discussed the intervention by community pharmacist in patient education and improved training on the correct instillation of eye drop. There are different aspects of application errors encountered by patients while using eye drop, particularly in glaucoma elderly patients, and polypharmacy. These application errors could lead to a diverse range of complications, such as poor medication, ocular infections, increased health care expenses, reduced treatment effectiveness, and lower health outcomes. There is a potential role of pharmacist-led interventions in minimising procedures associated with improper technique and application of eye drops to avoid decreased therapeutic response and treatment failure.

Advances in dorzolamide hydrochloride delivery: harnessing nanotechnology for enhanced ocular drug delivery in glaucoma management

Dorzolamide hydrochloride (DRZ) is a carbonic anhydrase inhibitor utilized in managing elevated intraocular pressure (IOP) associated with glaucoma. However, its clinical effectiveness is hindered by a short half-life, low residence time, and the need for frequent dosing, highlighting the necessity for innovative delivery systems. This work reviews recent advancements in DRZ delivery, particularly focusing on cyclodextrin complexation and nanotechnology applications. It explores the potential of cyclodextrin derivatives to enhance DRZ's bioavailability. DRZ cyclodextrin complexes or nanoparticulate systems maintain high drug concentrations in the eye while minimizing irritation and viscosity-related issues. Nanotechnology introduces nanoparticle-based carriers such as polymeric nanoparticles, solid lipid nanoparticles, liposomes, niosomes, and nanoemulsions. These formulations enable sustained drug release, improved corneal permeation, and enhanced patient compliance. Clinical trials have shown that DRZ nanoparticle eye drops and nanoliposome formulations offer efficacy comparable to conventional therapies, with the potential for better tolerability. Overall, this review highlights significant progress in DRZ delivery systems, suggesting their potential to transform glaucoma treatment by addressing current limitations and improving therapeutic outcomes.

Oleogels for the ocular delivery of epalrestat: formulation, in vitro, in ovo, ex vivo and in vivo evaluation

The ocular administration of lipophilic and labile drugs such as epalrestat, an aldose reductase inhibitor with potential for diabetic retinopathy treatment, demands the development of topical delivery systems capable of providing sufficient ocular bioavailability. The aim of this work was to develop non-aqueous oleogels based on soybean oil and gelators from natural and sustainable sources (ethyl cellulose, beeswax and cocoa butter) and to assess their reproducibility, safety and efficiency in epalrestat release and permeation both ex vivo and in vivo. Binary combinations of gelators at 10% w/w resulted in solid oleogels (oleorods), while single gelator oleogels at 5% w/w remained liquid at room temperature, with most of the oleogels displaying shear thinning behavior. The oleorods released up to 4 µg epalrestat per mg of oleorod in a sustained or burst pattern depending on the gelator (approx. 10% dose in 24 h). The HET-CAM assay indicated that oleogel formulations did not induce ocular irritation and were safe for topical ocular administration. Corneal and scleral ex vivo assays evidenced the permeation of epalrestat from the oleorods up to 4 and 2.5 µg/cm2 after six hours, respectively. Finally, the capacity of the developed oleogels to sustain release and provide significant amounts of epalrestat to the ocular tissues was demonstrated in vivo against aqueous-based niosomes and micelles formulations loaded with the same drug concentration. Overall, the gathered information provides valuable insights into the development of oleogels for ocular drug delivery, emphasizing their safety and controlled release capabilities, which have implications for the treatment of diabetic neuropathy and other ocular conditions.

Development of transferosomes for topical ocular drug delivery of curcumin

BACKGROUND

Transferosomes (TFS) are ultra-deformable elastic bilayer vesicles that have previously been used to enhance gradient driven penetration through the skin. This study aimed to evaluate the potential of TFS for topical ocular drug delivery and to compare their penetration enhancing properties in different ocular tissues.

METHODS

Curcumin-loaded TFS were prepared using Tween 80 as the edge activator. Drug release and precorneal retention of the TFS were evaluated in vitro, while their ocular biocompatibility and bioavailability were evaluated ex vivo using a curcumin solution in medium chain triglycerides as the oily control.

RESULTS

The TFS had a narrow size distribution with a particle size less than 150 nm and an entrapment efficiency greater than 99.96 %. Burst release from the TFS was minimal and the formulation showed good corneal biocompatibility. Moreover, enhanced corneal and conjunctival drug penetration with significantly greater and deeper drug delivery was observed with TFS in all ocular tissues.

CONCLUSION

TFS offer a promising platform for ocular delivery of hydrophobic drugs. This study, for the first time, elucidates the effect of tissue morphology and osmotic gradients on drug penetration in different ocular tissues.

Advancements in Ocular Therapy: A Review of Emerging Drug Delivery Approaches and Pharmaceutical Technologies

Eye disorders affect a substantial portion of the global population, yet the availability of efficacious ophthalmic drug products remains limited. This can be partly ascribed to a number of factors: (1) inadequate understanding of physiological barriers, treatment strategies, drug and polymer properties, and delivery systems; (2) challenges in effectively delivering drugs to the anterior and posterior segments of the eye due to anatomical and physiological constraints; and (3) manufacturing and regulatory hurdles in ocular drug product development. The present review discusses innovative ocular delivery and treatments, encompassing implants, liposomes, nanoparticles, nanomicelles, microparticles, iontophoresis, in situ gels, contact lenses, microneedles, hydrogels, bispecific antibodies, and gene delivery strategies. Furthermore, this review also introduces advanced manufacturing technologies such as 3D printing and hot-melt extrusion (HME), aimed at improving bioavailability, reducing therapeutic dosages and side effects, facilitating the design of personalized ophthalmic dosage forms, as well as enhancing patient compliance. This comprehensive review lastly offers insights into digital healthcare, market trends, and industry and regulatory perspectives pertaining to ocular product development.

Small Molecule Topical Ophthalmic Formulation Development-Data Driven Trends & Perspectives from Commercially Available Products in the US

Topical ophthalmic drug product development is a niche research domain as the drug formulations need to be designed to perform in the unique ocular physiological conditions. The most common array of small molecule drug formulations intended for topical ophthalmic administration include solutions, suspensions, emulsions, gels, and ointments. The formulation components such as excipients and container closure are unique to serve the needs of topical ophthalmic delivery compared to other parenteral products. The selection of appropriate formulation platform, excipients, and container closure for delivery of drugs by topical ophthalmic route is influenced by a combination of factors like physicochemical properties of the drug molecule, intended dose, pharmacological indication as well as the market trends influenced by the patient population. In this review, data from literature and packaging inserts of 118 reference listed topical ophthalmic medications marketed in the US are collected and analyzed to identify trends that would serve as a guidance for topical ophthalmic formulation development for small molecule drugs. Specifically, the topics reviewed include current landscape of the available small molecule topical ophthalmic drug products in the US, physicochemical properties of the active pharmaceutical ingredients (APIs), formulation platforms, excipients, and container closure systems.

Mechanism of Ocular Penetration of Lipophilic Drugs from Lipophilic Vehicles

Since eyedrops have conventionally been formulated in aqueous vehicles, ocular pharmacokinetic studies are generally performed using aqueous buffers to identify physicochemical properties of the drug and the vehicles that influence drug absorption. In recent years, biocompatible lipophilic vehicles are increasingly finding application in ocular drug delivery; however, the mechanism of drug penetration from these non-aqueous vehicles is poorly understood. This study aims to compare ocular penetration of the model lipophilic drug curcumin when incorporated into lipophilic vehicles. To elucidate whether intrinsic solubility in the lipophilic vehicle influences ocular penetration, a curcumin solution and suspension were prepared in medium chain triglycerides (MCT) and squalane, respectively. Ocular penetration and distribution of curcumin from both vehicles was compared and evaluated qualitatively and quantitatively ex vivo. Significantly greater and faster penetration was observed from the squalane suspension than from the MCT solution in all ocular tissues. Our results suggest that the ability of lipophilic drugs to partition out of lipophilic vehicles and into cell membranes, rather than their intrinsic solubility in the lipophilic vehicle, determines the rate and extent of their ocular penetration.

Tolerability of Current Treatments for Dry Eye Disease: A Review of Approved and Investigational Therapies

Dry eye disease (DED) is a common, multifactorial ocular disease impacting 5% to 20% of people in Western countries and 45% to 70% in Asian countries. Despite the prevalence of DED and the number of treatment approaches available, signs and symptoms of the disease continue to limit the quality of life for many patients. Standard over-the-counter treatment approaches and behavior/environmental modifications may help some cases but more persistent forms often require pharmacological interventions. Approved and investigational pharmaceutical approaches attempt to treat the signs and symptoms of DED in different ways and tend to have varying tolerability among patients. While several pharmacological approaches are the standard for persistent and severe disease, mechanical options provide alternate treatment modalities that attempt to balance efficacy and comfort. Newer approaches target the causes of DED, utilizing novel delivery methods to minimize irritation and adverse events. Here, we review approved and investigational approaches to treating DED and compare patient tolerability.

Ingestion of Fluids of the Ocular Surface Containing Eye Drops of Imidazole Derivatives-Alpha Adrenergic Receptor Agonists as Paragons

Accidental poisonings by ingesting conjunctival fluid mixed with eye drops commonly involve alpha-2 adrenergic receptor agonists and tetrahydrozoline. These substances are recognized in commonly reported ingestions. Victims of all ages, otherwise in good health, often present as pale and lethargic to the emergency department (ED) after unintentionally ingesting topical eye medication. While eye drop poisoning cases in childhood include accidents during the play and poisonings in adults mean either suicide attempts or side effects caused by the systemic absorption of the substance, fluid of the ocular surface is a risk to all age groups. With this in mind, this study aimed to summarize data in the literature on tetrahydrozoline and alpha-2 adrenergic receptor agonists as dangerous medications, even when administered in low-bioavailability forms, such as eye drops. With this aim, a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review of relevant studies was conducted. A search of PubMed, Scopus, Web of Science, and EBSCOhost yielded nine studies that met the rigorous inclusion criteria. The primary studies were subject to a meta-analysis once a quality appraisal of the studies and a narrative synthesis of the extracted data had been conducted. The author hopes that this information will provide observations that will lead to better designs for over-the-counter eye drops, off-label drug usage policies, and parental attention.

Engineering a novel water-in-oil biocompatible microemulsion system for the ocular delivery of dexamethasone sodium phosphate in the treatment of acute uveitis

Due to their unique characteristics, microemulsions (ME) represent one of the most promising delivery systems which can conquer poor ocular drug bioavailability providing long residence time. Development of a ME system, relying on the use of a safe and non-irritant surfactant combination derived from sustainable resources and which can consolidate the small ME droplets, is the goal of this work. Herein, we report the design and characterization of a novel biocompatible, eco-friendly ME system loaded with the hydrophilic dexamethasone sodium phosphate (DEXP) using a novel surfactant mixture composed of D-α-tocopherol polyethylene glycol succinate (TPGS) and Plantacare® (coco-Glycosides). Capryol™ PGMC and double-distilled water were used as the respective oil and aqueous phases and the MEs were prepared by the water titration method, suitable for scaling up. Optimization of ME formulae was conducted by varying Plantacare® grades, TPGS to Plantacare® mass ratios and drug loading. The formulae were characterized in terms of physical appearance, droplet size (PS), size distribution (PDI), zeta potential (ZP), and stability. The optimized DEXP-loaded ME formula attained acceptable PS, PDI, and ZP values of 43 ± 5 nm, 0.35 ± 0.07, -12 ± 4 mV, respectively. TEM images confirmed a small PS ≤ 100 nm. The in vivo safety of ME was proved by the Draize test. The ME formula prompted excellent mucoadhesion and transcorneal permeation. The confocal studies showed deep penetration into the rabbits' corneas. In vivo studies using endotoxin-induced uveitis showed high ocular efficacy and a significant reduction in inflammatory cells, including interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). The obtained results elect the novel engineered ME system as a promising tool for the ocular delivery of hydrophilic moieties in the management of various ophthalmic diseases.

Progress in Ocular Drug Delivery: Challenges and Constraints

The eye has several dynamic and static barriers in place to limit the entry of foreign substances including therapeutics. As such, efficient drug delivery, especially to posterior segment tissues, has been challenging. This chapter describes the anatomical and physiological challenges associated with ocular drug delivery before discussing constraints with regard to formulation parameters. Finally, it gives an overview of advanced drug delivery technologies with a specific focus on recently marketed and late-stage clinical trial products.