Ophthalmic drug design based on the metabolic activity of the eye: soft drugs and chemical delivery systems

Geriatric drug delivery - barriers, current technologies and the road ahead

The geriatric population encompasses the largest part of the health care system worldwide. Chronic medical conditions are highly prevalent in the elderly, consequently, due to their complex health needs, there is a significant rate of multi-drug therapy. Despite the high numbers of medications prescribed, geriatric patients face several barriers when it comes to successful drug delivery including alterations in cognitive and physical function. The current review highlights the impact of chronic diseases on the ageing population along with how changes in drug pharmacokinetics could impact drug efficacy and safety. Also discussed are applications of administration routes in the geriatric population and complications that could arise. A focus is placed on the traditional and upcoming drug delivery advancements being employed in seniors with a focus addressing obstacles faced by this patient category. Nanomedicines, three-dimensional printing, long-acting formulations, transdermal systems, orally disintegrating tablets, and shape/taste modification technologies are discussed. Several barriers to drug delivery in the elderly have been identified in literature and directions for future studies should focus on addressing these gaps for geriatric drug formulation development including personalised medicine, insights into novel drug delivery systems like nanomedicines, methods for decreasing pill burden and shape/size modifications.ARTICLE HIGHLIGHTSTypically, senior citizens take more medications than any other patient population, yet most drug delivery technologies are not tailored to address the specific cognitive and physical barriers that these individuals encounter.The safety of drug delivery systems in the elderly patients should be prioritised with considerations on changes in pharmacokinetics with age, use of non-toxic excipients, and selecting drugs with minimal off-target side effects.Several commercialised and upcoming drug delivery technologies have begun to address the current limitations that the ageing population faces.Future research should focus on applying novel strategies like 3D printing, personalised medicine, and long-acting formulations to improve drug delivery to elderly patients.

Fabrication of Anti-glaucoma Nanofibers as Controlled-Release Inserts for Ophthalmic Delivery of Brimonidine Tartrate: In Vivo Evaluation in Caprine Eye

Purpose

Chronic ailments usually decrease the quality of life due to the requirement for repetitive administration of drugs. Glaucoma is a chronic eye disease occurred because of increased intraocular pressure (IOP). Controlled-release inserts can overcome this challenge by a gradual release of the antiglaucoma drugs. This study aimed to fabricate ocular inserts of brimonidine tartrate (BMD) for the management of glaucoma.

Methods

Different polymers including poly (D, L-lactide), polycaprolactone, cellulose acetate, and Eudragit RL100® were used to develop the BMD-loaded nanofibrous inserts by electrospinning technique. The inserts were characterized. The morphology and drug-polymer compatibility were examined by scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy and in vitro drug release in PBS. The IOP-lowering efficacy and irritancy of optimized formulation were assessed in the caprines.

Results

SEM images demonstrated nanofibers with uniform morphology and a mean diameter<300 nm were fabricated. The nanofibers were high-strength and flexible enough to be placed in the conjunctival sac. FTIR showed drug-polymer compatibility. In vitro release study indicated a sustained-release profile of the drug during 6 days for inserts. In vivo evaluation indicated that the optimized formulation is capable of maintaining the IOP in a non-glaucomatous range for an extended duration of 6 days. In addition, the formulation was non-irritant to the caprine eye.

Conclusion

Due to the prolonged IOP-lowering efficiency, BMD-loaded nanofibrous inserts can be considered suitable for the controlled release of drugs and thus enhance patient compliance by reducing the frequency of administration.

Principle, application and challenges of development siRNA-based therapeutics against bacterial and viral infections: a comprehensive review

While significant progress has been made in understanding and applying gene silencing mechanisms and the treatment of human diseases, there have been still several obstacles in therapeutic use. For the first time, ONPATTRO, as the first small interfering RNA (siRNA) based drug was invented in 2018 for treatment of hTTR with polyneuropathy. Additionally, four other siRNA based drugs naming Givosiran, Inclisiran, Lumasiran, and Vutrisiran have been approved by the US Food and Drug Administration and the European Medicines Agency for clinical use by hitherto. In this review, we have discussed the key and promising advances in the development of siRNA-based drugs in preclinical and clinical stages, the impact of these molecules in bacterial and viral infection diseases, delivery system issues, the impact of administration methods, limitations of siRNA application and how to overcome them and a glimpse into future developments.

The Efficacy and Safety of Standard versus Soft Topical Steroids after Cataract Surgery: A Systematic Review and Meta-analysis

TOPIC

Review of the efficacy and safety of standard versus soft topical steroid application after cataract surgery.

CLINICAL RELEVANCE

The control of postoperative inflammation is the mainstay of treatment after cataract surgery. However, no consensus exists regarding the postoperative steroid of choice. Basing the choice of topical postoperative steroidal treatment on high-quality data regarding both risks and benefits of various drugs would be advantageous for both patients and clinicians.

METHODS

A systematic search of the PubMed, Scopus, and Embase electronic databases for all peer-reviewed published randomized control trials that included clinical outcomes of topical steroidal treatment after uneventful cataract surgery was performed. Individual study data were extracted and evaluated in a weighted pooled analysis including grading of total anterior chamber (AC) inflammation, AC cells, AC flare, postoperative visual acuity (VA), intraocular pressure (IOP), and rate of adverse events (AEs).

RESULTS

Overall, 508 studies were found, of which 7 were eligible for the systematic review and ultimately were included for analysis, reporting on 593 patients from 5 countries. Age of included patients, when available, ranged between 3.7 and 73.4 years. Follow-up data were available for analysis at 1, 7, and 28 days after surgery. Except for a significantly lower grade of AC flare in the standard steroid group at day 7 (standardized mean difference, 0.26; 95% confidence interval, 0.05-0.47; I2 = 0%), inflammatory activity measurements displayed insignificant differences at every other follow-up (days 1 and 28 after surgery). Pooled analysis of IOP at each follow-up demonstrated a higher IOP at the 7-day visit in the standard steroid group, whereas IOP at other time points was comparable among the groups. Qualitative analysis of ocular AEs showed similarities among the groups.

DISCUSSION

The findings of this study suggest that for the average patient, both groups produce a comparable effect on both AC inflammation and postoperative IOP and VA.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Genetically determined metabolites in allergic conjunctivitis: A Mendelian randomization study

Background

Allergic conjunctivitis (AC) afflicts a significant portion of the global populace. Yet, its metabolic foundations remain largely unexplored.

Methods

We applied Mendelian Randomization (MR) and Linkage Disequilibrium Score Regression (LDSC) to scrutinize a cohort comprising 20 958 AC cases and 356 319 controls. Data were amalgamated from the metabolomics GWAS server and the FinnGen project, under strict quality control protocols.

Results

Using two-sample MR analysis, 486 blood metabolites were investigated in relation to AC. The IVW approach highlighted 18 metabolites as closely tied to AC risk; of these, 16 retained significance post sensitivity assessments for heterogeneity and horizontal pleiotropy. LDSC analysis, adopted to bolster our findings and negate confounders from shared genetic markers, revealed 8 metabolites with marked heritability, including: palmitate (OR = 0.614), 3-methoxytyrosine (OR = 0.657), carnitine (OR = 1.368), threonate (OR = 0.828), N-[3-(2-Oxopyrrolidin-1-yl)propyl]acetamide (OR = 1.257), metoprolol acid metabolite (OR = 0.982), oleoylcarnitine (OR = 0.635), and 2-palmitoylglycerophosphocholine (OR = 1.351).

Conclusion

AC is precipitated by ocular responses to environmental allergens. Our study unveils a causal link between 8 blood metabolites and AC. This insight accentuates the role of metabolites in AC onset, suggesting novel avenues for its early prediction, targeted prevention, and tailored therapeutic interventions.

Neoteric Role of Quercetin in Visual Disorders

Flavonoids are a family of secondary metabolites found in plants and fungi that exhibit strong antioxidant properties and low toxicity, making them potential candidates for medicinal use. Quercetin, a flavonoid present in various plant-based foods, has gained attention for its numerous biological benefits, including anti-inflammatory, anti-fibrosis, and antioxidant properties. The ocular surface research community has recently focused on quercetin's therapeutic potential for managing ocular diseases, such as dry eye, keratoconus, corneal inflammation, and neovascularization. In this paper, we discuss the role of quercetin for ocular disease prevention, highlighting its fundamental characteristics, common biological properties, and recent applications. By reviewing the latest research conducted in the last 10 years which was focused on novel herbal formulations for ocular diseases, we aim to provide insights into the role of quercetin in managing ocular diseases and offer perspectives on its potential as a therapeutic agent.

In Vitro and In Vivo Safety of Hyaluronic Acid-Decorated Microparticles for Intravitreal Injection of Palmitoylethanolamide, Citicoline, or Glial-Cell-Derived Neurotrophic Factor

The treatment of posterior eye segment diseases through intravitreal injection requires repeated injections of an active molecule, which may be associated with serious side effects and poor patient compliance. One brilliant strategy to overcome these issues is the use of drug-loaded microparticles for sustained release, aiming at reducing the frequency of injections. Therefore, the aim of this work was to assess the safety features of poly(lactic-co-glycolic acid) (PLGA)-based, hyaluronic acid-decorated microparticles loaded with palmitoylethanolamide (PEA), citicoline (CIT), or glial-cell-derived neurotrophic factor (GDNF). Microparticles were prepared by double emulsion-solvent evaporation and fully characterized for their technological features. Microparticles possessed a satisfactory safety profile in vitro on human retinal pigment epithelial (ARPE-19) cells. Interestingly, the administration of free GDNF led to a loss of cell viability, while GDNF sustained release displayed a positive effect in that regard. In vivo results confirmed the safety profile of both empty and loaded microparticles. Overall, the outcomes suggest that the produced microparticles are promising for improving the local administration of neuroprotective molecules. Further studies will be devoted to assess the therapeutic ability of microparticles.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

Glaucoma is a chronic optic neuropathy that can lead to irreversible functional and morphological damage if left untreated. The gold standard therapeutic approaches in managing patients with glaucoma and limiting progression include local drops, laser, and/or surgery, which are all geared at reducing intraocular pressure (IOP). Nutrients, antioxidants, vitamins, organic compounds, and micronutrients have been gaining increasing interest in the past decade as integrative IOP-independent strategies to delay or halt glaucomatous retinal ganglion cell degeneration. In our minireview, we examine the various nutrients and compounds proposed in the current literature for the management of ophthalmology diseases, especially for glaucoma. With respect to each substance considered, this minireview reports the molecular and biological characteristics, neuroprotective activities, antioxidant properties, beneficial mechanisms, and clinical studies published in the past decade in the field of general medicine. This study highlights the potential benefits of these substances in glaucoma and other ophthalmologic pathologies. Nutritional supplementation can thus be useful as integrative IOP-independent strategies in the management of glaucoma and in other ophthalmologic pathologies. Large multicenter clinical trials based on functional and morphologic data collected over long follow-up periods in patients with IOP-independent treatments can pave the way for alternative and/or coadjutant therapeutic options in the management of glaucoma and other ocular pathologies.

Eudragit® L100/Polyvinyl Alcohol Nanoparticles Impregnated Mucoadhesive Films as Ocular Inserts for Controlled Delivery of Erythromycin: Development, Characterization and In Vivo Evaluation

The fast elimination of drugs from the cornea is one of many challenges associated with the topical administration of conventional dosage forms. The present manuscript aimed to prepare modified-release inserts containing erythromycin (ERY) to enhance drug delivery and address the aforementioned limitation. Film formulations were developed using Eudragit^® L100 (EUD) and Polyvinyl Alcohol (PVA) polymers. ERY-loaded EUD-based nanoparticles were developed by the colloidal dispersion method using PVA as the emulsifier. The film-casting method was applied to form the mucoadhesive films using sodium alginate, gelatin, cyclodextrin-α, and β as polymeric film matrices. Different physicochemical properties of the optimized formulations and in vitro release profiles were evaluated. The in vivo evaluation was performed by collecting tear samples of rabbits using a novel, non-invasive method following the administration of inserts in the cul-de-sac. The ERY amount was assayed using a microbiological assay. The developed films showed prolonged in vitro and in vivo release profiles over five to six days; they had suitable physicochemical properties and a tensile strength of 2–3 MPa. All formulations exhibited antibacterial efficacy against E. coli and S. aureus with more than 20 mm diameter of inhibited growth zones. None of the formulations caused irritation to the rabbit’s eye. The inserts showed promising pharmacokinetics with AUC_0–120 of 30,000–36,000 µg·h/mL, a C_max of more than 1800 µg/mL at 4 h, and maintained drug concentration over the threshold of 5 µg/mL during the following 120 h of study. Nanoparticle-containing, mucoadhesive films could be fabricated as ocular inserts and can prolong the topical ocular delivery of ERY.

Treatment of Non-Infectious Corneal Injury: Review of Diagnostic Agents, Therapeutic Medications, and Future Targets

Corneal injuries can occur secondary to traumatic, chemical, inflammatory, metabolic, autoimmune, and iatrogenic causes. Ocular infection may frequently occur concurrent to corneal injury; however, antimicrobial agents are excluded from this present review. While practitioners may primarily rely on clinical examination techniques to assess these injuries, several pharmacological agents, such as fluorescein, lissamine green, and rose bengal, can be used to formulate a diagnosis and develop effective treatment strategies. Practitioners may choose from several analgesic medications to help with patient comfort without risking further injury or delaying ocular healing. Atropine, cyclopentolate, scopolamine, and homatropine are among the most frequently used medications for this purpose. Additional topical analgesic agents may be used judiciously to augment patient comfort to facilitate diagnosis. Steroidal anti-inflammatory agents are frequently used as part of the therapeutic regimen. A variety of commonly used agents, including prednisolone acetate, loteprednol, difluprednate, dexamethasone, fluorometholone, and methylprednisolone are discussed. While these medications are effective for controlling ocular inflammation, side effects, such as elevated intraocular pressure and cataract formation, must be monitored by clinicians. Non-steroidal medications, such as ketorolac, bromfenac, nepafenac, and diclofenac, are additionally used for their efficacy in controlling ocular inflammation without incurring side effects seen with steroids. However, these agents have their own respective side effects, warranting close monitoring by clinicians. Additionally, ophthalmologists routinely employ several agents in an off-label manner for supplementary control of inflammation and treatment of corneal injuries. Patients with corneal injuries not infrequently have significant ocular surface disease, either as a concurrent pathology or as an exacerbation of previously existing disease. Several agents used in the management of ocular surface disease have also been found to be useful as part of the therapeutic armamentarium for treatment of corneal injuries. For example, several antibiotics, such as doxycycline and macrolides, have been used for their anti-inflammatory effects on specific cytokines that are upregulated during acute injuries. There has been a recent wave of interest in amniotic membrane therapies (AMTs), including topical, cryopreserved and dehydrated variants. AMT is particularly effective in ocular injuries with violation of corneal surface integrity due to its ability to promote re-epithelialization of the corneal epithelium. Blood-based therapies, including autologous serum tears, plasma-enriched growth factor eyedrops and autologous blood drops, have additionally been explored in small case series for effectiveness in challenging and recalcitrant cases. Protection of the ocular surface is also a vital component in the treatment of corneal injuries. Temporary protective methods, such as bandage contact lenses and mechanical closure of the eyelids (tarsorrhaphy) can be particularly helpful in selective cases. Glue therapies, including biologic and non-biologic variants, can also be used in cases of severe injury and risk of corneal perforation. Finally, there are a variety of recently introduced and in-development agents that may be used as adjuvant therapies in challenging patient populations. Neurotrophic corneal disease may occur as a result of severe or chronic injury. In such cases, recombinant human nerve growth factor (cenegermin), topical insulin, and several other novel agents may be an alternate and effective option for clinicians to consider.

Ocular Distribution of Papaverine Using Non-aqueous Vehicles

Papaverine, a poorly soluble opium alkaloid, has recently been shown to reduce retinal inflammation due to which it may have therapeutic application in the management of Leber's hereditary optic neuropathy. In this study, papaverine eyedrops based on medium chain triglycerides were prepared and the effect of diethyl glycol monoethyl ether (DGME) on their ocular distribution was evaluated using an ex vivo porcine eye model. The route of drug penetration was also studied by orienting the eye to expose either only the cornea or the sclera to the formulation. Furthermore, in vivo studies were performed to confirm ocular tolerability and evaluate ocular drug distribution. Our results showed increased papaverine concentrations in the cornea and sclera in the presence of DGME but with a slight reduction in the retina-choroid (RC) drug concentration when administered via the corneal route, suggesting that DGME enhances drug accumulation in the anterior ocular tissues but with little effect on posterior drug delivery. In vivo, the papaverine eyedrop with DGME showed good ocular tolerability with the highest drug concentration being observed in the cornea (1.53 ± 0.28 μg/g of tissue), followed by the conjunctiva (0.74 ± 0.18 μg/g) and sclera (0.25 ± 0.06 μg/g), respectively. However, no drug was detected in the RC, vitreous humor or plasma. Overall, this study highlighted that DGME influences ocular distribution and accumulation of papaverine. Moreover, results suggest that for hydrophobic drugs dissolved in hydrophobic non-aqueous vehicles, transcorneal penetration via the transuveal pathway may be the predominant route for drug penetration to posterior ocular tissues. Graphical abstract.

The therapeutic use of quercetin in ophthalmology: recent applications

Quercetin is a natural flavonol antioxidant found in various plant sources and food samples. It is well known for its notable curative effects on the treatment of ophthalmic diseases due to various biological activities, such as antioxidant, anti-inflammatory, and anti-fibrosis activities. This review will discuss the latest developments in therapeutic quercetin for the treatment of keratoconus, Graves' orbitopathy, ocular surface, cataracts, glaucoma, retinoblastoma, and other retinal diseases.

Small interfering RNAs (siRNAs) based gene silencing strategies for the treatment of glaucoma: Recent advancements and future perspectives

RNA-interference-based mechanisms, especially the use of small interfering RNAs (siRNAs), have been under investigation for the treatment of several ailments and have shown promising results for ocular diseases including glaucoma. The eye, being a confined compartment, serves as a good target for the delivery of siRNAs. This review focuses on siRNA-based strategies for gene silencing to treat glaucoma. We have discussed the ocular structures and barriers to gene therapy (tear film, corneal, conjunctival, vitreous, and blood ocular barriers), methods of administration for ocular gene delivery (topical instillation, periocular, intracameral, intravitreal, subretinal, and suprachoroidal routes) and various viral and non-viral vectors in siRNA-based therapy for glaucoma. The components and mechanism of siRNA-based gene silencing have been mentioned briefly followed by the basic strategies and challenges faced during siRNA therapeutics development. We have emphasized different therapeutic targets for glaucoma which have been under research by scientists and the current siRNA-based drugs used in glaucoma treatment. We also mention briefly strategies for siRNA-based treatment after glaucoma surgery.

Corticosteroids in ophthalmology: drug delivery innovations, pharmacology, clinical applications, and future perspectives

Corticosteroids remain the mainstay of the treatment for various ocular conditions affecting the ocular surface, anterior and posterior segments of the eye due to their anti-inflammatory, anti-oedematous, and anti-neovascularization properties. Prednisolone, prednisolone acetate, dexamethasone, triamcinolone acetonide, fluocinolone acetonide, and loteprednol etabonate are amongst the most widely used ophthalmic corticosteroids. Corticosteroids differ in their activity and potency in the eye due to their inherent pharmacological and pharmaceutical differences. Different routes and regimens are available for ocular administration of corticosteroids. Conventional topical application to the eye is the route of choice when targeting diseases affecting the ocular surface and anterior segment, while periocular, intravitreal, and suprachoroidal injections can be potentially effective for posterior segment diseases. Corticosteroid-induced intraocular pressure elevation and cataract formation remain the most significant local risks following topical as well as systemic corticosteroid administration. Invasive drug administration via intracameral, subconjunctival, and intravitreal injection can enhance ocular bioavailability and minimize dose and dosing frequency of administration, yet may exacerbate ocular side effects of corticosteroids. This review provides a critical appraisal of the ophthalmic uses of corticosteroid, routes of administration, drug delivery fundamentals and novel ocular implantable steroid delivery systems, factors influencing side effects, and future perspectives for ocular corticosteroid therapy.

Charged Tags for the Identification of Oxidative Drug Metabolites Based on Electrochemistry and Mass Spectrometry

Most of the active pharmaceutical ingredients like Metoprolol are oxidatively metabolized by liver enzymes, such as Cytochrome P450 monooxygenases into oxygenates and therefore hydrophilic products. It is of utmost importance to identify the metabolites and to gain knowledge on their toxic impacts. By using electrochemistry, it is possible to mimic enzymatic transformations and to identify metabolic hot spots. By introducing charged-tags into the intermediate, it is possible to detect and isolate metabolic products. The identification and synthesis of initially oxidized metabolites are important to understand possible toxic activities. The gained knowledge about the metabolism will simplify interpretation and predictions of metabolitic pathways. The oxidized products were analyzed with high performance liquid chromatography-mass spectrometry using electrospray ionization (HPLC-ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy. For proof-of-principle, we present a synthesis of one pyridinated main oxidation product of Metoprolol.

Stability analysis of drug dynamics model: A mathematical approach

In this paper, a mathematical model of drug release from polymeric matrix and consequent intracellular drug transport is proposed and analyzed. Modeling of drug release is done through solubilization dynamics of drug particles, diffusion of the solubilized drug through the polymeric matrix in addition to reversible dissociation/recrystallization process. The interaction between drug-receptor, drug-plasma proteins along with other intracellular endosomal events is modeled. This leads to a mixed system of partial and ordinary differential equations with associated pertinent set of initial and boundary conditions. Furthermore, besides the stability of the proposed model, several sub-models are also studied for their stability criteria. Prominence is provided to the reduced model system having requisite relevance to the original system where quasi steady state approximation (QSSA) theory is utilized. For the model to be potent enough to generate appropriate predictive results for drug delivery, the stability properties of equilibrium in the mathematical model are analyzed both analytically and numerically. Numerical simulation in the embodiment of graphical representations speaks about various vital characteristics of the underlying physical phenomena along with the importance and sensitized impact of the model parameters controlling significant biological functions. Probed new therapies and clinical procedures could be assessed considering the present mathematical model and its analysis as the basis framework in order to effectively enhance therapeutic efficacy and improved patient compliance. The present study confirms the necessity of stability analysis study so that advocated mathematical model can effectively complement the real physiological behavior of pharmacokinetics.

Nanomaterials-Based siRNA Delivery: Routes of Administration, Hurdles and Role of Nanocarriers

Ribonucleic acid interference (RNAi) is a potential alternative therapeutic approach to knock down the overexpression of genes in several disorders especially cancers with underlying genetic dysfunctions. For silencing of specific genes involved in cell cycle, small/short interfering ribonucleic acids (siRNAs) are being used clinically. The siRNA-based RNAi is more efficient, specific and safe antisense technology than other RNAi approaches. The route of siRNA administration for siRNA therapy depends on the targeted site. However, certain hurdles like poor stability of siRNA, saturation, off-target effect, immunogenicity, anatomical barriers and non-targeted delivery restrict the successful siRNA therapy. Thus, advancement of an effective, secure, and long-term delivery system is prerequisite to the medical utilization of siRNA. Polycationic nanocarriers mediated targeted delivery system is an ideal system to remove these hurdles and to increase the blood retention time and rate of intracellular permeability. In this chapter, we will mainly discuss the different biocompatible, biodegradable, non-toxic (organic, inorganic and hybrid) nanocarriers that encapsulate and shield the siRNA from the different harsh environment and provides the increased systemic siRNA delivery.

A Nonlinear Mathematical Model of Drug Delivery from Polymeric Matrix

The objective of the present study is to mathematically model the integrated kinetics of drug release in a polymeric matrix and its ensuing drug transport to the encompassing biological tissue. The model embodies drug diffusion, dissolution, solubilization, polymer degradation and dissociation/recrystallization phenomena in the polymeric matrix accompanied by diffusion, advection, reaction, internalization and specific/nonspecific binding in the biological tissue. The model is formulated through a system of nonlinear partial differential equations which are solved numerically in association with pertinent set of initial, interface and boundary conditions using suitable finite difference scheme. After spatial discretization, the system of nonlinear partial differential equations is reduced to a system of nonlinear ordinary differential equations which is subsequently solved by the fourth-order Runge-Kutta method. The model simulations deal with the comparison between a drug delivery from a biodegradable polymeric matrix and that from a biodurable polymeric matrix. Furthermore, simulated results are compared with corresponding existing experimental data to manifest the efficaciousness of the advocated model. A quantitative analysis is performed through numerical computation relied on model parameter values. The numerical results obtained reveal an estimate of the effects of biodegradable and biodurable polymeric matrices on drug release rates. Furthermore, through graphical representations, the sensitized impact of the model parameters on the drug kinetics is illustrated so as to assess the model parameters of significance.

Development of simultaneous quantification method of loteprednol etabonate (LE) and its acidic metabolites, and analysis of LE metabolism in rat

Loteprednol etabonate (LE) is a soft corticosteroid with two labile ester bonds at 17α- and 17β-positions. Its corticosteroidal activity disappears upon hydrolysis of either ester bond. Hydrolysis of both ester bonds produces the inactive metabolite, Δ¹-cortienic acid (Δ¹-CA). The simple high-performance liquid chromatography method using acetic acid gradient was developed for the simultaneous determination of LE and its acidic metabolites. LE was hydrolyzed in rat plasma with a half-life of 9 min. However, LE hydrolysis was undetectable in rat liver and intestine. LE hydrolysis in rat plasma was completely inhibited by paraoxon and bis(p-nitrophenyl) phosphate, thus identifying carboxylesterase as the LE hydrolase. Rat plasma carboxylesterase had a K_m of 6.7 μM for LE. In contrast to the disappearance rate of LE in rat plasma, the formation rate of 17α-monoester and Δ¹-CA was markedly low, and a main hydrolysate of LE was not detected in rat plasma. The metabolism of LE proceeded via different pathways in human and rat plasma. LE was slowly hydrolyzed by paraoxonase in human plasma to 17α-monoester with a half-life of 12 h, but by carboxylesterase in rat plasma to yield undetectable products, presumed to include the unstable 17β-monoester.

Loteprednol etabonate for inflammatory conditions of the anterior segment of the eye: twenty years of clinical experience with a retrometabolically designed corticosteroid

INTRODUCTION

Topical corticosteroids are an important pharmacotherapy for the management of various inflammatory conditions affecting the anterior segment of the eye. However, medications in this class are associated with well-known risks including increased intraocular pressure (IOP) and development of cataracts. The topical corticosteroid loteprednol etabonate (LE) was developed with the specific intention of minimizing these side effects.

AREAS COVERED

The focus of this review is to examine published efficacy and safety data for LE, a drug engineered to undergo rapid metabolism to inactive metabolites with the goal of improved safety. Two decades of clinical research focused on LE formulations are reviewed, including the use of LE in combination with tobramycin. The cumulative body of experience affirms the concept that the molecular design of LE confers certain safety benefits without compromising the desired anti-inflammatory efficacy of a topical corticosteroid.

EXPERT OPINION

Loteprednol etabonate is a mainstay for topical therapy of a wide variety of commonplace and niche conditions of the ocular surface and the anterior segment, including in the healing post-operative patient. Its versatility and safety allow eye care providers to recommend both acute induction as well as chronic maintenance therapy with appropriate follow-up.

In vitro and ex vivo correlation of drug release from ophthalmic ointments

In vitro drug release testing and ex vivo transcorneal drug permeation can provide valuable information on the performance of the Q1/Q2 equivalent ointments prior to any animal studies. Good correlation between in vitro and ex vivo drug release may be indicative of good in vitro and in vivo correlation. Accordingly, it is important to investigate in vitro as well as ex vivo drug release from Q1/Q2 equivalent ophthalmic ointments and evaluate whether a correlation between these release profiles can be established. Four Q1/Q2 equivalent loteprednol etabonate ointments were prepared using different processing methods and excipient sources. The rheological parameters (crossover modulus and K value) of the four formulations were determined. The in vitro drug release testing of the four ointment formulations were performed using three different apparati (Franz diffusion cells, USP apparatus 2 with enhancer cells and USP apparatus 4 with semisolid adapters). Three models (zero order, logarithmic and the Higuchi model) were used to study the release kinetics of the ointment formulations. The transcorneal (rabbit corneas) permeation studies were performed using spherical joint Franz diffusion cells. The USP apparatus 4 method demonstrated better discriminatory ability compared to the USP apparatus 2 and the Franz diffusion cell methods. The in vitro release profiles of the four Q1/Q2 equivalent ointments with manufacturing differences showed a better fit using the Higuchi model (R² > 0.98) for all three release testing methods, compared to the other two models. Ex vivo drug release through the rabbit corneas displayed zero order release kinetics. A logarithmic correlation between rheological parameters (crossover and K value) and transcorneal flux were established. In addition, a plot of the in vitro release rate against the ex vivo release flux of the four ointment formulations, yielded a straight line (R² > 0.98) for all three release methods. Accordingly, the rheological parameters may be useful in predicting in vitro as well as ex vivo release properties.

An analytical study of drug release kinetics from a degradable polymeric matrix

In modern days, biodegradable polymeric matrix used as the kingpin of local drug delivery system is in the center of attention. This work is concentrated on the formulation of mathematical model elucidating degradation of drug-loaded polymeric matrix followed by drug release to the adjacent biological tissues. Polymeric degradation is penciled with mass conservation equations. Drug release phenomenon is modeled by considering solubilization dynamics of drug particles, diffusion of the solubilized drug through polymeric matrix along with reversible dissociation/recrystallization process. In the tissue phase, reversible dissociation/association along with internalization processes of drug are taken into account. For this, a two-phase spatio-temporal model is postulated, which has ensued to a system of partial differential equations. They are solved analytically with appropriate choice of initial, interface and boundary conditions. In order to reflect the potency of the advocated model, the simulated results are analogized with corresponding experimental data and found laudable agreement so as to validate the applicability of the model considered. This model seems to foster the delicacy of the mantle enacted by important drug kinetic parameters such as diffusion coefficients, mass transfer coefficients, particle binding and internalization parameters, which is illustrated through local sensitivity analysis.

Pharmacologic Management of Pressure-Induced Stromal Keratopathy after LASIK

PURPOSE

To emphasize the importance of anticipation of pressure-induced stromal keratopathy (PISK) in eyes with a previous history of LASIK.

CASE REPORT

A 40-year-old man developed LASIK-related pressure-induced stromal keratopathy after uneventful phacoemulsification (Phaco) and intraocular lens (IOL) implantation in his left eye. With immediate discontinuation of the steroid drops and initiation of antiglaucoma medication, his visual acuity, interface edema, and haze improved rapidly. One year later, during Phaco with IOL implantation in his other eye, with anticipation of a similar LASIK-related pressure-induced stromal keratopathy, a very brief course of soft steroid therapy was given together with antiglaucoma medication. Intraocular pressure elevation was avoided, and no interface edema or haze was observed.

CONCLUSIONS

This case illustrates that the risk for LASIK-related pressure-induced stromal keratopathy may be reduced with appropriate precautions.

Ocular non-P450 oxidative, reductive, hydrolytic, and conjugative drug metabolizing enzymes

Metabolism in the eye for any species, laboratory animals or human, is gaining rapid interest as pharmaceutical scientists aim to treat a wide range of so-called incurable ocular diseases. Over a period of decades, reports of metabolic activity toward various drugs and biochemical markers have emerged in select ocular tissues of animals and humans. Ocular cytochrome P450 (P450) enzymes and transporters have been recently reviewed. However, there is a dearth of collated information on non-P450 drug metabolizing enzymes in eyes of various preclinical species and humans in health and disease. In an effort to complement ocular P450s and transporters, which have been well reviewed in the literature, this review is aimed at presenting collective information on non-P450 oxidative, hydrolytic, and conjugative ocular drug metabolizing enzymes. Herein, we also present a list of xenobiotics or drugs that have been reported to be metabolized in the eye.

Potential Use of Cyclodextrin Complexes for Enhanced Stability, Anti-inflammatory Efficacy, and Ocular Bioavailability of Loteprednol Etabonate

Loteprednol etabonate (LE) is a soft corticosteroid that maintains therapeutic activity with much reduced adverse effects. Yet, its ocular bioavailability is hindered by its poor aqueous solubility. Early attempts of LE complexation with cyclodextrins (CDs) did not involve the study of the effects of various complexation methods on the characteristics of the complexes formed. Formulation of complexes into different delivery systems as well in vitro and in vivo assessments has not been accomplished in the earlier studies. In this study, complexation of LE with each of hydroxypropyl-β-cyclodextrin (HP-β-CD) and β-cyclodextrin (β-CD) by kneading, freeze drying, and co-precipitation was attempted. These complexes were incorporated into gels, drops, and ocuserts using hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and sodium alginate (ALG). These formulae were examined with respect to drug content, pH, viscosity, in vitro release, and stability for 6 months. Kinetic analysis of release data was done. Selected formulations were assessed for their efficacy in the treatment of ocular allergic conjunctivitis and their ocular bioavailability in rabbits' eyes. All formulations exhibited accepted drug content, pH, and viscosity. The drug release was increased by complexation particularly with HP-β-CD in the order of ocuserts ≥ drops > gels, being the highest for HPMC preparations that also exhibited the greatest stability and anti-inflammatory activity especially in case of LE-HP-β-CD complexes. Ocuserts of co-precipitated LE-HP-β-CD using HPMC (5% w/w) and Carbopol 934P (0.1% w/w) provided a significantly enhanced stability (p < 0.05), ocular anti-inflammatory efficacy (p < 0.05), and ocular bioavailability (p < 0.0001), to be represented as a potential ocular delivery system of LE.

Advances in the use of prodrugs for drug delivery to the eye

INTRODUCTION

Ocular drug delivery is presented with many challenges, taking into account the distinctive structure of the eye. The prodrug approach has been, and is being, employed to overcome such barriers for some drug molecules, utilizing a chemical modification approach rather than a formulation-based approach. A prodrug strategy involves modification of the active moiety into various derivatives in a fashion that imparts some advantage, such as membrane permeability, site specificity, transporter targeting and improved aqueous solubility, over the parent compound. Areas covered: The following review is a comprehensive summary of various novel methodologies and strategies reported over the past few years in the area of ocular drug delivery. Some of the strategies discussed involve polymer and lipid conjugation with the drug moiety to impart hydrophilicity or lipophilicity, or to target nutrient transporters by conjugation with transporter-specific moieties and retrometabolic drug design. Expert opinion: The application of prodrug strategies provides an option for enhancing drug penetration into the ocular tissues, and overall ocular bioavailability, with minimum disruption of the ocular diffusion barriers. Although success of the prodrug strategy is contingent on various factors, such as the chemical structure of the parent molecule, aqueous solubility and solution stability, capacity of targeted transporters and bioreversion characteristics, this approach has been successfully utilized, commercially and therapeutically, in several cases.

Impact of the Topical Ophthalmic Corticosteroid Loteprednol Etabonate on Intraocular Pressure

Corticosteroids are a mainstay therapeutic option for the treatment of ocular inflammation. However, safety remains a concern for clinicians, particularly with long-term use. Though highly effective at suppressing inflammatory and allergic responses, topical ophthalmic corticosteroids carry an inherent risk of side effects, including elevated intraocular pressure (IOP), a risk factor for the development of glaucoma. The corticosteroid loteprednol etabonate (LE) contains an ester rather than a ketone at the C-20 position, minimizing the potential for side effects, including IOP elevation. In early pivotal clinical trials of LE ophthalmic suspension for conjunctivitis (allergic, giant papillary), anterior uveitis, and post-operative inflammation, LE had minimal impact on IOP over short-term (<28 days) and long-term (≥28 days) use. Since then, new LE formulations—including a gel, an ointment, and a suspension of LE in combination with tobramycin—have become commercially available. Multiple studies evaluating the safety and efficacy of LE for inflammatory conditions have been reported, including those requiring longer-term treatment such as photorefractive keratectomy, corneal transplantation, and dry eye disease. We review the available published data on the effect of LE on IOP and report on the cumulative incidence of clinically significant IOP elevations (≥10 mm Hg from baseline) with short-term and long-term LE use. In all studies, LE consistently demonstrated a low propensity to elevate IOP, regardless of formulation, dosage regimen, or treatment duration, including in known steroid responders. The cumulative proportion of patients exhibiting clinically significant IOP increases was 0.8% (14/1725 subjects) in studies evaluating short-term LE treatment and 1.5% (21/1386 subjects) in long-term studies. Furthermore, use of LE was associated with significantly lower rates of IOP elevation ≥10 mm Hg as compared to prednisolone acetate or dexamethasone (when used in combination with tobramycin). The cumulative data to date substantiates a favorable IOP-safety profile for LE with both short-term and long-term use.

Symptomatic Treatment of Subepithelial Infiltrates after Viral Conjunctivitis: Loteprednol or Dexamethasone?

PURPOSE

To compare the efficiency and ocular side-effect profile of topical loteprednol applied to one eye and topical dexamethasone applied to the other eye in the early period on the same patient who has subepithelial infiltrates (SEI).

METHODS

The patients who developed bilateral SEI following epidemic keratoconjunctivitis (EKC) were applied topical loteprednol on one eye (group 2) and topical dexamethasone on the other (group 1).

RESULTS

Decrease in the symptoms was faster in the dexamethasone group, but this difference between the groups was not statistically significant (p = 0.073). Both groups were found to have substantial recurrence. However, the difference between the groups was not statistically significant (p = 0.131).

CONCLUSIONS

The study has found that in the treatment of SEI, which developed after EKC, statistically similar results can be obtained with loteprednol, which is known to have fewer adverse effects.

Rho Kinase (ROCK) Inhibitors and Their Therapeutic Potential

Rho kinases (ROCKs) belong to the serine-threonine family, the inhibition of which affects the function of many downstream substrates. As such, ROCK inhibitors have potential therapeutic applicability in a wide variety of pathological conditions including asthma, cancer, erectile dysfunction, glaucoma, insulin resistance, kidney failure, neuronal degeneration, and osteoporosis. To date, two ROCK inhibitors have been approved for clinical use in Japan (fasudil and ripasudil) and one in China (fasudil). In 1995 fasudil was approved for the treatment of cerebral vasospasm, and more recently, ripasudil was approved for the treatment of glaucoma in 2014. In this Perspective, we present a comprehensive review of the physiological and biological functions for ROCK, the properties and development of over 170 ROCK inhibitors as well as their therapeutic potential, the current status, and future considerations.

Topical Ocular Drug Delivery to the Back of the Eye by Mucus-Penetrating Particles

PURPOSE

Enhanced drug exposure to the ocular surface typically relies on inclusion of viscosity-enabling agents, whereas delivery to the back of the eye generally focuses on invasive means, such as intraocular injections. Using our novel mucus-penetrating particle (MPP) technology, which rapidly and uniformly coats and penetrates mucosal barriers, we evaluated if such drug formulations could increase ocular drug exposure and improve topical drug delivery.

METHODS

Pharmacokinetic (PK) profiling of topically administered loterprednol etabonate formulated as MPP (LE-MPP) was performed in rabbits and a larger species, the mini-pig. Pharmacodynamic evaluation was done in a rabbit model of VEGF-induced retinal vascular leakage. Cellular potency and PK profile were determined for a second compound, KAL821, a novel receptor tyrosine kinase inhibitor (RTKi).

RESULTS

We demonstrated in animals that administration of LE-MPP increased exposure at the ocular surface and posterior compartments. Furthermore using a rabbit vascular leakage model, we demonstrated that biologically effective drug concentrations of LE were delivered to the back of the eye using the MPP technology. We also demonstrated that a novel RTKi formulated as MPPs provided drug levels to the back of the eye above its cellular inhibitory concentration.

CONCLUSIONS

Topical dosing of MPPs of LE or KAL821 enhanced drug exposure at the front of the eye, and delivered therapeutically relevant drug concentrations to the back of the eye, in animals.

TRANSLATIONAL RELEVANCE

These preclinical data support using MPP technology to engineer topical formulations to deliver therapeutic drug levels to the back of the eye and could provide major advancements in managing sight-threatening diseases.

Chemical delivery systems and soft drugs: Retrometabolic approaches of drug design

Inclusion of metabolic considerations in the drug design process leads to significant development in the field of chemical drug targeting and the design of safer drugs during past few years which is a part of an approach now designated as Retro metabolic drug design (RMDD). This approach represents systematic methodologies that integrate structure-activity and structure-metabolism relationships and are aimed to design safe, locally active compounds with an improved therapeutic index. It embraces two distinct methods, chemical delivery systems and a soft drug approach. Present review recapitulates an impression of RMDD giving reflections on the chemical delivery system and the soft drug approach and provides a variety of examples to embody its concepts. Successful application of such design principles has already been applied to a number of marketed drugs like esmolol; loteprednol etc., and many other candidates like beta blockers, ACE inhibitors, alkylating agents, antimicrobials etc., are also under investigation.

C-ring cannabinoid lactones: a novel cannabinergic chemotype

As a part of our controlled-deactivation ligand development project, we recently disclosed a series of (-)-Δ(8)-tetrahydrocannabinols (THCs) with a metabolically labile ester group at the 2'-position of the side chain. Now, we have replaced the C-ring in the classical THC structure with a hydrolyzable seven-membered lactone. One of the synthesized analogues binds with high affinity to the CB1 receptor (K i = 4.6 nM) and exhibits much lower affinities for the mCB2 and the hCB2. Also, in vitro functional characterization found the compound to be an agonist at rCB1. Consistent with our rational design, the lead cannabinergic lactone identified here is susceptible to metabolic inactivation by plasma esterases, while the respective acid metabolite is inactive at CB receptors. These results are highlighted with molecular modeling of the two regiosomeric lactones.

Ocular Pharmacokinetics of a Novel Loteprednol Etabonate 0.4% Ophthalmic Formulation

Introduction

Topical ophthalmic formulations of corticosteroids are commonly used to treat a variety of ocular diseases and conditions that have an inflammatory component. The purpose of this study was to evaluate the effect of the mucus-penetrating particle (MPP) technology on the pharmacokinetic profile of loteprednol etabonate in the ocular tissues of rabbits.

Methods

Forty-eight New Zealand White rabbits were randomly assigned to two groups (n = 3 rabbits or 6 eyes per time point) and treated with either the novel loteprednol etabonate MPP suspension formulation, 0.4% (LE-MPP 0.4%), or the commercial Lotemax^®-brand loteprednol etabonate ophthalmic suspension, 0.5% (Lotemax 0.5%) (Bausch & Lomb Incorporated, Inc., Rochester, NY, USA). Samples of aqueous humor, various ocular tissues, and plasma were collected from animals over a 12-h period after a single dose of the test articles. Loteprednol etabonate concentrations were assayed using liquid chromatography–tandem mass spectrometry (LC/MS/MS).

Results

Loteprednol etabonate was rapidly absorbed into ocular tissues following administration of either formulation. A higher ocular exposure was achieved using LE-MPP 0.4%, with peak concentrations of approximately threefold higher in ocular tissues and the aqueous humor than Lotemax 0.5%.

Conclusions

Administration of LE-MPP 0.4% improved loteprednol etabonate pharmacokinetic profile in ocular tissues of rabbits. The results of this study support the premise that the MPP technology can be used to enhance ocular exposure for topically applied therapeutic agents. Further studies to assess the clinical efficacy and safety of the LE-MPP formulation are warranted.

Electronic supplementary material

The online version of this article (doi:10.1007/s40123-014-0021-z) contains supplementary material, which is available to authorized users.

Anterior eye segment drug delivery systems: current treatments and future challenges

New technologies for delivery of drugs, such as small molecules and biologics, are of growing interest among clinical and pharmaceutical researchers for use in treating anterior segment eye disease. The challenge is to deliver effective drugs at therapeutic concentrations to the targeted ocular tissue with minimal side effects. To achieve this, a better understanding of the unmet needs, what is required of the various methods of delivery to achieve successful delivery, and the potential challenges of anterior segment drug delivery is necessary and the primarily aim of this review. This review covers the various physiological and anatomical barriers that exist for effective delivery to the targeted tissue of the eye, the pathological conditions of the anterior segment, and the unmet needs for treatment of these ocular diseases. Second, it reviews the novel delivery technologies that have the potential to maintain and/or improve the drug's therapeutic index and improving both patient adherence for chronic therapy and potential patient outcomes. This review bridges the pharmaceutical and clinical research/challenges and provides a detailed overview of anterior segment drug delivery accomplishments thus far, for researchers and clinicians.

Prolonged exposure to loteprednol etabonate in human tear fluid and rabbit ocular tissues following topical ocular administration of Lotemax gel, 0.5%

PURPOSE

A new gel formulation containing loteprednol etabonate (LE), a C-20 ester corticosteroid used to treat ocular inflammation, was developed to provide increased retention on the ocular surface for improved drug delivery to intraocular tissues. This investigation evaluated concentrations of LE in tear fluid following topical instillation of LE gel to humans and the ocular and systemic pharmacokinetics of LE following administration to rabbits.

METHODS

LE ophthalmic gel 0.5% was administered as a single topical dose to human volunteers (n=12) and Dutch Belted rabbits (n=40). In the human study, tear sampling was performed at 6, 9, 12, and 24 h after instillation. In the rabbit study, tears and ocular tissues were collected from 5 min through 24 h postdose. Serial blood samples were collected from one cohort of rabbits for plasma analysis. Concentrations of LE were determined by high performance liquid chromatography tandem mass spectrometry.

RESULTS

In humans, LE was detected in tears at all the time points assessed with mean concentrations of 114 μg/g at 6 h declining to 2.41 μg/g at 24 h postdose. In rabbits, LE was detected in all ocular tissues within 5 min after dosing. Maximum concentrations of LE were achieved within 0.5 h and were highest in tear fluid (1560 μg/g), followed by bulbar conjunctiva (4.03 μg/g), cornea, (2.18 μg/g), iris/ciliary body (0.162 μg/g), and aqueous humor (0.0138 μg/mL). LE remained measurable in all ocular tissues through 24 h with the exception of aqueous humor. In contrast, plasma levels of LE were low with no detectable levels after 4 h.

CONCLUSIONS

The gel formulation of LE provided prolonged exposure to LE on the ocular surface, with measurable levels in tears through 24 h in both humans and rabbits, for delivery of LE to anterior segment tissues, as evidenced by sustained levels of LE in rabbit conjunctiva, cornea, and iris/ciliary body.

Dose uniformity of loteprednol etabonate ophthalmic gel (0.5%) compared with branded and generic prednisolone acetate ophthalmic suspension (1%)

Introduction

Loteprednol etabonate (LE) ophthalmic gel 0.5% (Lotemax®) is a new polycarbophil-based, nonsettling topical ophthalmic formulation. The formulation is a semisolid gel at rest and a shear thinning fluid when expressed through a dropper tip. The present study was undertaken to determine how the nonsettling character of LE ophthalmic gel affects dose uniformity. Prednisolone acetate ophthalmic suspension 1% (Pred Forte®) and a generic prednisolone acetate suspension 1% were used as comparators.

Methods

Drug concentrations of LE ophthalmic gel, Pred Forte, and a generic prednisolone acetate suspension were determined following simulated dosing – consisting of 2 drops, expressed four times daily for 2 weeks, with bottles that were shaken or not shaken immediately prior to expressing the drops. Drug concentrations were determined using a reverse-phase high-performance liquid chromatography (HPLC) method and reported as a percentage of the declared (labeled) concentration. Comparative kinetics of drug particle sedimentation were also determined for each formulation, using dispersion analysis under gravity.

Results

Mean drug concentrations in drops of all three formulations were within a few percentage points of the declared concentration when the bottles were shaken for 5 seconds prior to dispensing. Only LE ophthalmic gel showed consistent and on-target concentrations when the bottles were unshaken prior to dispensing, with a mean (standard deviation [SD]) percent declared concentration of 102% (1.92%) over the 2-week dosing regimen. Drug concentrations for the branded and generic prednisolone acetate suspensions following expression from unshaken bottles were highly variable (overall relative SDs of 16.8% and 20.3%, respectively), with mean concentrations for both falling significantly below the declared concentration for drops expressed at the beginning of the 2-week dosing regimen and significantly above the declared concentration for drops expressed near the end of the dosing regimen. Dispersion analysis at 120× g showed no drug particle sedimentation for LE ophthalmic gel over the 24-hour testing period, whereas the prednisolone acetate suspensions settled in less than 6 hours.

Conclusion

LE ophthalmic gel 0.5% provided consistent dose uniformity at the declared concentration whether or not the bottle was shaken prior to dispensing, whereas Pred Forte® and the generic prednisolone acetate required shaking to provide consistent drug concentrations. LE ophthalmic gel may be beneficial to patients because it eliminates the potential impact on the clinical response of both under- and overdosing.

Controlled-deactivation cannabinergic ligands

We report an approach for obtaining novel cannabinoid analogues with controllable deactivation and improved druggability. Our design involves the incorporation of a metabolically labile ester group at the 2'-position on a series of (-)-Δ(8)-THC analogues. We have sought to introduce benzylic substituents α to the ester group which affect the half-lives of deactivation through enzymatic activity while enhancing the affinities and efficacies of individual ligands for the CB1 and CB2 receptors. The 1'-(S)-methyl, 1'-gem-dimethyl, and 1'-cyclobutyl analogues exhibit remarkably high affinities for both CB receptors. The novel ligands are susceptible to enzymatic hydrolysis by plasma esterases in a controllable manner, while their metabolites are inactive at the CB receptors. In further in vitro and in vivo experiments key analogues were shown to be potent CB1 receptor agonists and to exhibit CB1-mediated hypothermic and analgesic effects.

Intraocular pressure effects of common topical steroids for post-cataract inflammation: are they all the same?

The efficacy of topical corticosteroids as ocular anti-inflammatory agents following cataract surgery is well-documented. They also help to prevent a number of complications associated with post-operative ocular inflammation, including corneal edema and cystoid macular edema. However, topical corticosteroids are associated with side effects, such as increased intraocular pressure (IOP). Indeed, corticosteroid-induced ocular hypertension and the potential for steroid-induced glaucoma remain the leading drawbacks of topical corticosteroid therapy. Some individuals are known to experience a high degree of IOP elevation with low doses or short durations of treatment with topical corticosteroids. Careful monitoring of IOP in such individuals is essential. Few randomized, controlled studies are available on the comparative safety and efficacy of common topical corticosteroids in the treatment of post-operative ocular inflammation. Furthermore, the lack of consistent reporting criteria for clinically significant IOP increases across clinical studies makes meaningful comparisons among corticosteroids difficult. This review aims to examine data from available published studies, including studies in steroid responders, to determine whether topical corticosteroids are the same in terms of their effect on IOP. Early generation corticosteroids, such as dexamethasone and prednisolone, are more likely to result in clinically significant increases in IOP. Newer corticosteroids, such as rimexolone and the retro-metabolically designed corticosteroid, loteprednol etabonate, offer similar anti-inflammatory efficacy to older corticosteroids with less effect on IOP. However, randomized controlled trials of newer corticosteroids are needed. The proportion of patients exhibiting an increase of ≥10 mmHg IOP in clinical studies has emerged as the most clinically relevant parameter for ophthalmologists to consider when deciding on which topical corticosteroid to use.

Stabilization and sustained release of zeylenone, a soft cytotoxic drug, within polymeric micelles for local antitumor drug delivery

Use of soft drugs has resulted in mixed success with the applicability to chemotherapeutics yet being confirmed. We hypothesize that incorporation of a soft cytotoxic agent into polymeric micelles, which confer to stabilizing and sustained release effect, will improve and prolong the local antitumor efficacy, thus achieving the therapeutic potential of soft cytotoxic agents. We incorporated a model soft cytotoxic agent, zeylenone, into mPEG-PLGA micelles by solvent evaporation method. The drug loaded micelles were characterized in terms of drug encapsulation, dynamic size, zeta potential, drug stability and in vitro and in vivo release. The in vivo antitumor efficacy was evaluated in A549 tumor-bearing mice. Zeylenone-loaded micelles exhibited core-shell morphology with dynamic size of about 36 nm and offered efficient solubilizing and stabilizing effects. In vitro release and in vivo pharmacokinetic results indicated sustained release of zeylenone in micelles. In addition, local delivered zeylenone-loaded micelles showed improved and sustained antitumor effect in vivo, compared with intravenous administration or local delivery of free drug solution. This study demonstrates the feasibility of soft cytotoxic agent to achieve local antitumor efficacy after the drug was stabilized and sustained the release within polymeric micelles.

Delivery systems and local administration routes for therapeutic siRNA

With the increasing number of studies proposing new and optimal delivery strategies for the efficacious silencing of gene-related diseases by the local administration of siRNAs, the present review aims to provide a broad overview of the most important and latest developments of non-viral siRNA delivery systems for local administration. Moreover, the main disease targets for the local delivery of siRNA to specific tissues or organs, including the skin, the lung, the eye, the nervous system, the digestive system and the vagina, were explored.