Sustained release ocular drug delivery systems for glaucoma therapy

Nanomedicine in glaucoma treatment; Current challenges and future perspectives

Glaucoma presents a significant global health concern and affects millions of individuals worldwide and predicted a high increase in prevalence of about 111 million by 2040. The current standard treatment involves hypotensive eye drops; however, challenges such as patient adherence and limited drug bioavailability hinder the treatment effectiveness. Nanopharmaceuticals or nanomedicines offer promising solutions to overcome these obstacles. In this manuscript, we summarized the current limitations of conventional antiglaucoma treatment, role of nanomedicine in glaucoma treatment, rational design, factors effecting the performance of nanomedicine and different types of nanocarriers in designing of nanomedicine along with their applications in glaucoma treatment from recent literature. Current clinical challenges that hinder real-time application of antiglaucoma nanomedicine are highlighted. Lastly, future directions are identified for improving the therapeutic potential and translation of antiglaucoma nanomedicine into clinic.

ROS-responsive charge reversal mesoporous silica nanoparticles as promising drug delivery system for neovascular retinal diseases

Intravitreal injection of biodegradable implant drug carriers shows promise in reducing the injection frequency for neovascular retinal diseases. However, current intravitreal ocular devices have limitations in adjusting drug release rates for individual patients, thereby affecting treatment effectiveness. Accordingly, we developed mesoporous silica nanoparticles (MSNs) featuring a surface that reverse its charge in response to reactive oxygen species (ROS) for efficient delivery of humanin peptide (HN) to retinal epithelial cells (ARPE-19). The MSN core, designed with a pore size of 2.8 nm, ensures a high HN loading capacity 64.4% (w/w). We fine-tuned the external surface of the MSNs by incorporating 20% Acetyl-L-arginine (Ar) to create a partial positive charge, while 80% conjugated thioketal (TK) methoxy polyethylene glycol (mPEG) act as ROS gatekeeper. Ex vivo experiments using bovine eyes revealed the immobilization of Ar-MSNs-TK-PEG (mean zeta potential: 2 mV) in the negatively charged vitreous. However, oxidative stress reversed the surface charge to -25 mV by mPEG loss, facilitating the diffusion of the nanoparticles impeded with HN. In vitro studies showed that ARPE-19 cells effectively internalize HN-loaded Ar-MSNs-TK, subsequently releasing the peptide, which offered protection against oxidative stress-induced apoptosis, as evidenced by reduced TUNEL and caspase3 activation. The inhibition of retinal neovascularization was further validated in an in vivo oxygen-induced retinopathy (OIR) mouse model.

Lipid-Gelucire based rectal delivery of ramipril prodrug exhibits significant lowering of intra-ocular pressure in normotensive rabbit: sustained structural relaxation release kinetics and IVIVC

Carboxylesterase enzymes convert a prodrug ramipril into the biologically active metabolite ramiprilat. It is prescribed for controlling ocular hypertension after oral administration. High concentrations of carboxylesterase enzymes in rectal and colon tissue can transform ramipril significantly to ramiprilat. Sustained rectal delivery of ramipril has been developed for intra-ocular pressure lowering effect using a normotensive rabbit model. Rectal suppositories have been formulated using a matrix base of HPMC K100-PEG 400-PEG 6000, incorporating varying amounts of Gelucire by the fusion moulding method. The presence of Gelucire in the suppository exhibited sustained structural relaxation-based release kinetics of RM compared to its absence. Intravenous and oral administration of ramipril has decreased IOP in the treated rabbit up to 90 and 360 min, respectively. Treated rabbits with suppositories have revealed decreased IOP for an extended period compared to the above. Formulation containing GEL 3% reduced intra-ocular pressure to 540 min, with the highest area under the decreased IOP curve. Compared to oral, the pharmacodynamic bioavailability of ramipril has been improved significantly using a sustained-release rectal suppository. A rectal suppository for sustained delivery of ramipril could be used to lower IOP significantly.

Microparticles and multi-unit systems for advanced drug delivery

Microparticles have unique benefits in the formulation of multiparticulate and multi-unit type pharmaceutical dosage forms allowing improved drug safety and efficacy with favorable pharmacokinetics and patient centricity. On the other hand, the above advantages are served by high and well reproducible quality attributes of the medicinal product where even flexible design and controlled processability offer success as well as possible longer product life-cycle for the manufacturers. Moreover, the specific demands of patients can be taken into account, including simplified dosing regimens, flexible dosage, drug combinations, palatability, and ease of swallowing. In the more than 70 years since the first modified-release formulation appeared on the market, many new formulations have been marketed and many publications have appeared in the literature. More unique and newer pharmaceutical technologies and excipients have become available for producing tailor-made particles with micrometer dimensions and beyond. All these have contributed to the fact that the sub-units (e.g. minitablets, pellets, microspheres) that make up a multiparticulate system can vary widely in composition and properties. Some units have mucoadhesive properties and others can float to contribute to a suitable release profile that can be designed for the multiparticulate formula as a whole. Nowadays, there are some available formulations on the market, which are able to release the active substance even for several months (3 or 6 months depending on the type of treatment). In this review, the latest developments in technologies that have been used for a long time are presented, as well as innovative solutions such as the applicability of 3D printing to produce subunits of multiparticulate systems. Furthermore, the diversity of multiparticulate systems, different routes of administration are also presented, touching the ones which are capable of carrying the active substance as well as the relevant, commercially available multiparticle-based medical devices. The versatility in size from 1 µm and multiplicity of formulation technologies promise a solid foundation for the future applications of dosage form design and development.

Overview of processed excipients in ocular drug delivery: Opportunities so far and bottlenecks

Ocular drug delivery presents a unique set of challenges owing to the complex anatomy and physiology of the eye. Processed excipients have emerged as crucial components in overcoming these challenges and improving the efficacy and safety of ocular drug delivery systems. This comprehensive overview examines the opportunities that processed excipients offer in enhancing drug delivery to the eye. By analyzing the current landscape, this review highlights the successful applications of processed excipients, such as micro- and nano-formulations, sustained-release systems, and targeted delivery strategies. Furthermore, this article delves into the bottlenecks that have impeded the widespread adoption of these excipients, including formulation stability, biocompatibility, regulatory constraints, and cost-effectiveness. Through a critical evaluation of existing research and industry practices, this review aims to provide insights into the potential avenues for innovation and development in ocular drug delivery, with a focus on addressing the existing challenges associated with processed excipients. This synthesis contributes to a deeper understanding of the promising role of processed excipients in improving ocular drug delivery systems and encourages further research and development in this rapidly evolving field.

Alternatives to Topical Glaucoma Medication for Glaucoma Management

Topical glaucoma medications have favorable safety and efficacy, but their use is limited by factors such as side effects, nonadherence, costs, ocular surface disease, intraocular pressure fluctuations, diminished quality of life, and the inherent difficulty of penetrating the corneal surface. Although traditionally these limitations have been accepted as an inevitable part of glaucoma treatment, a rapidly-evolving arena of minimally invasive surgical and laser interventions has initiated the beginnings of a reevaluation of the glaucoma treatment paradigm. This reevaluation encompasses an overall shift away from the reactive, topical-medication-first default and a shift toward earlier intervention with laser or surgical therapies such as selective laser trabeculoplasty, sustained-release drug delivery, and micro-invasive glaucoma surgery. Aside from favorable safety, these interventions may have clinically important attributes such as consistent IOP control, cost-effectiveness, independence from patient adherence, prevention of disease progression, and improved quality of life.

Technological Advances in a Therapy of Primary Open-Angle Glaucoma: Insights into Current Nanotechnologies

Glaucoma is a leading cause of irreversible blindness and is characterized by increased intraocular pressure (IOP) and progressive optic nerve damage. The current therapeutic approaches for glaucoma management, such as eye drops and oral medications, face challenges including poor bioavailability, low patient compliance, and limited efficacy. In recent years, nanotechnology has emerged as a promising approach to overcome these limitations and revolutionize glaucoma treatment. In this narrative review, we present an overview of the novel nanotechnologies employed in the treatment of primary open-angle glaucoma. Various nanosystems, including liposomes, niosomes, nanoparticles, and other nanostructured carriers, have been developed to enhance the delivery and bioavailability of antiglaucoma drugs. They offer advantages such as a high drug loading capacity, sustained release, improved corneal permeability, and targeted drug delivery to the ocular tissues. The application of nanotechnologies in glaucoma treatment represents a transformative approach that addresses the limitations of conventional therapies. However, further research is needed to optimize the formulations, evaluate long-term safety, and implement these nanotechnologies into clinical practice. With continued advancements in nanotechnology, the future holds great potential for improving the management and outcomes of glaucoma, ultimately preserving vision and improving the lives of millions affected by this debilitating disease.