Breaking Barriers: Nanomedicine-Based Drug Delivery for Cataract Treatment

Cataract is a leading cause of blindness globally, and its surgical treatment poses a significant burden on global healthcare. Pharmacologic therapies, including antioxidants and protein aggregation reversal agents, have attracted great attention in the treatment of cataracts in recent years. Due to the anatomical and physiological barriers of the eye, the effectiveness of traditional eye drops for delivering drugs topically to the lens is hindered. The advancements in nanomedicine present novel and promising strategies for addressing challenges in drug delivery to the lens, including the development of nanoparticle formulations that can improve drug penetration into the anterior segment and enable sustained release of medications. This review introduces various cutting-edge drug delivery systems for cataract treatment, highlighting their physicochemical properties and surface engineering for optimal design, thus providing impetus for further innovative research and potential clinical applications of anti-cataract drugs.

Computational Model of In Vivo Corneal Pharmacokinetics and Pharmacodynamics of Topically Administered Ophthalmic Drug Products

INTRODUCTION

Although the eye is directly accessible on the surface of the human body, drug delivery can be extremely challenging due to the presence of multiple protective barriers in eye tissues. Researchers have developed complex formulation strategies to overcome these barriers to ophthalmic drug delivery. Current development strategies rely heavily on in vitro experiments and animal testing to predict human pharmacokinetics (PK) and pharmacodynamics (PD).

OBJECTIVE

The primary objective of the study was to develop a high-fidelity PK/PD model of the anterior eye for topical application of ophthalmic drug products.

METHODS

Here, we present a physiologically-based in silico approach to predicting PK and PD in rabbits after topical administration of ophthalmic products. A first-principles based approach was used to describe timolol dissolution, transport, and distribution, including consideration of ionized transport, following topical instillation of a timolol suspension.

RESULTS

Using literature transport and response parameters, the computational model described well the concentration-time and response-time profiles in rabbit. Comparison of validated rabbit model results and extrapolated human model results demonstrate observable differences in the distribution of timolol at multiple time points.

CONCLUSION

This modeling framework provides a tool for model-based prediction of PK in eye tissues and PD after topical ophthalmic drug administration to the eyes.

Nanotechnology for Topical Drug Delivery to the Anterior Segment of the Eye

Topical drug delivery is one of the most challenging aspects of eye therapy. Eye drops are the most prevalent drug form, especially for widely distributed anterior segment eye diseases (cataracts, glaucoma, dry eye syndrome, inflammatory diseases, etc.), because they are convenient and easy to apply by patients. However, conventional drug formulations are usually characterized by short retention time in the tear film, insufficient contact with epithelium, fast elimination, and difficulties in overcoming ocular tissue barriers. Not more than 5% of the total drug dose administered in eye drops reaches the interior ocular tissues. To overcome the ocular drug delivery barriers and improve drug bioavailability, various conventional and novel drug delivery systems have been developed. Among these, nanosize carriers are the most attractive. The review is focused on the different drug carriers, such as synthetic and natural polymers, as well as inorganic carriers, with special attention to nanoparticles and nanomicelles. Studies in vitro and in vivo have demonstrated that new formulations could help to improve the bioavailability of the drugs, provide sustained drug release, enhance and prolong their therapeutic action. Promising results were obtained with drug-loaded nanoparticles included in in situ gel.

Atorvastatin-loaded solid lipid nanoparticles as eye drops: proposed treatment option for age-related macular degeneration (AMD)

Statins, widely prescribed for cardiovascular diseases, are also being eyed for management of age-related macular degeneration (AMD). Poor bioavailability and blood-aqueous barrier may however limit significant ocular concentration of statins following oral administration. We for the first time propose and investigate local application of atorvastatin (ATS; representative statin) loaded into solid lipid nanoparticles (SLNs), as self-administrable eye drops. Insolubility, instability, and high molecular weight > 500 of ATS, and ensuring that SLNs reach posterior eye were the challenges to be met. ATS-SLNs, developed (2339/DEL/2014) using suitable components, quality-by-design (QBD) approach, and scalable hot high-pressure homogenization, were characterized and evaluated comprehensively for ocular suitability. ATS-SLNs were 8 and 12 times more bioavailable (AUC) in aqueous and vitreous humor, respectively, than free ATS. Three-tier (in vitro, ex vivo, and in vivo) ocular safety, higher corneal flux (2.5-fold), and improved stability (13.62 times) including photostability of ATS on incorporation in ATS-SLNs were established. Autoclavability and aqueous nature are the other highlights of ATS-SLNs. Presence of intact fluorescein-labeled SLNs (F-SLNs) in internal eye tissues post–in vivo application as eye drops provides direct evidence of successful delivery. Perinuclear fluorescence in ARPE-19 cells confirms the effective uptake of F-SLNs. Prolonged residence, up to 7 h, was attributed to the mucus-penetrating nature of ATS-SLNs.

Enhancement in corneal permeability of riboflavin using cyclodextrin derivates complexes as a previous step to transepithelial cross-linking

Corneal cross-linking has been described as an effective treatment to slow the progression of keratoconus. The standard protocol entails corneal epithelial removal to allow the diffusion of riboflavin into the stroma. Although, de-epithelization can generate risks or complications that transepithelial cross-linking tries to solve or avoid. Different formulations were developed after verifying that hydroxypropyl-β-cyclodextrin (HPβCD) and sulfobuthylether-β-cyclodextrin (SBEβCD) in a 20% concentration, increased the solubility of practically insoluble in water drugs such as riboflavin from 0.12 mg/mL to 0.35 mg/mL and 0.29 mg/mL respectively. These values were higher when chitosan and arginine were added to the formulation, showing solubility of 0.78 mg/mL when HPβCD concentration was not modified. Ex vivo corneal permeability was measured after having kept in contact bovine corneas with intact epithelium for 5 h with the 0.1 mg/mL riboflavin solution, the formulations developed and a reproduced nanoemulsion from another work. Riboflavin's permeability was increased when cyclodextrins, chitosan, and arginine were part of the formulations, compared to the control drug solution. The best permeability coefficient was reached when riboflavin was combined with 40% (w/v) HPβCD, 0.5% (w/w) arginine, and 0.5% (w/w) chitosan. After having carried out toxicity studies as bovine corneal opacity and permeability (BCOP) and Heńs Egg Test - Chorioallantoic Membrane Test (HET-CAM) it was verified that both, the active ingredients and the excipients of the different formulations were not harmful without generating irritation, loss of transparency or corneal permeability alterations. The results show the great potential of the ocular developed solution for their use in transepithelial cross-linking for keratoconus treatment.

Diffusion and Protein Corona Formation of Lipid-Based Nanoparticles in the Vitreous Humor: Profiling and Pharmacokinetic Considerations

The vitreous humor is the first barrier encountered by intravitreally injected nanoparticles. Lipid-based nanoparticles in the vitreous are studied by evaluating their diffusion with single-particle tracking technology and by characterizing their protein coronae with surface plasmon resonance and high-resolution proteomics. Single-particle tracking results indicate that the vitreal mobility of the formulations is dependent on their charge. Anionic and neutral formulations are mobile, whereas larger (>200 nm) neutral particles have restricted diffusion, and cationic particles are immobilized in the vitreous. PEGylation increases the mobility of cationic and larger neutral formulations but does not affect anionic and smaller neutral particles. Convection has a significant role in the pharmacokinetics of nanoparticles, whereas diffusion drives the transport of antibodies. Surface plasmon resonance studies determine that the vitreal corona of anionic formulations is sparse. Proteomics data reveals 76 differentially abundant proteins, whose enrichment is specific to either the hard or the soft corona. PEGylation does not affect protein enrichment. This suggests that protein-specific rather than formulation-specific factors are drivers of protein adsorption on nanoparticles in the vitreous. In summary, our findings contribute to understanding the pharmacokinetics of nanoparticles in the vitreous and help advance the development of nanoparticle-based treatments for eye diseases.

Current Regulation for Bioequivalence Evaluations of Generic Ophthalmic Dosage Forms in Japan

In Japan, the revised version of bioequivalence (BE) evaluations for generic drug products was made available in 2012; however, the scope of this guideline is mainly oral solid dosage forms. Other dosage forms have to be discussed regarding how to evaluate BE by applicants and regulators during consultation meetings or the review process. Recently, there has been an increase in developing generic drug products in various dosage forms in Japan. Therefore, the Pharmaceuticals and Medical Devices Agency (PMDA) must strengthen their efforts to establish methodologies for BE evaluations for various dosage forms, including those of ophthalmic drugs. In 2016, the Japanese Ministry of Health, Labour and Welfare (MHLW) issued "The basic principles of bioequivalence evaluations of generic ophthalmic aqueous solutions." This document presents recommendations for clinical endpoint BE studies or biowaiver options to evaluate the BE of generic ophthalmic aqueous solutions. However, this document has brought other issues to the forefront, such as the lack of feasibility of human BE studies for certain indications. Therefore, the PMDA, Japan Ophthalmic Pharmaceutical Manufacturer's Association, and BE experts discussed these issues for 2 years, which led to an update by MHLW in 2018 entitled "The basic principles of bioequivalence evaluations of generic ophthalmic dosage forms." This document describes methodologies for evaluating the BE of ophthalmic dosage forms including suspensions. This article introduces recently approved generic products of ophthalmic dosage forms in Japan, the basic principle of which was issued in 2018, and compares the BE evaluations between the PMDA and U.S. Food and Drug Administration.

Ocular Drug Delivery Systems Using Contact Lenses

The use of contact lenses as ocular drug delivery systems has been considered intuitive for decades. However, at this time, there are no approved products using such systems. In this article, we review the challenges with current therapies, pharmacokinetics, and pharmacodynamics of different drug classes and the patient population. In addition, we note the relative lack of clinical studies, and list potential products in active development at this time. In particular, we address the alignment of time course of the therapeutic need, the pharmacokinetics of the molecule, and the delivery characteristics of the systems (e.g., pulsatile vs. zero-order). We also discuss the needs of various populations including the elderly (who may have motor and cognitive issues as well as presbyopia) and the young. While a contact lens delivery system may also provide refractive correction, to date, most of the studies have used noncorrective (plano) lenses. We also considered nanotechnology-based carrier systems. We generalize the development of contact lens delivery systems to all ocular delivery systems in which there are relatively few product approvals and long development times.

Micelles: Promising Ocular Drug Carriers for Anterior and Posterior Segment Diseases

Micelles have been studied in the targeting of drug substances to different tissues as a nano-sized delivery system for many years. Sustained drug release, ease of production, increased solubility, and bioavailability of drugs with low water solubility are the most important superiorites of micellar carriers. These advantages paved the way for the use of micelles as a drug delivery system in the ocular tissues. The unique anatomical structure of the eye as well as its natural barriers and physiology affect ocular bioavailability of the drugs negatively. Conventional dosage forms can only reach the anterior segment of the eye and are used for the treatment of diseases of this segment. In the treatment of posterior segment diseases, conventional dosage forms are administered sclerally, via an intravitreal injection, or systemically. However, ocular irritation, low patient compliance, and high side effects are also observed. Micellar ocular drug delivery systems have significant promise for the treatment of ocular diseases. The potential of micellar systems ocular drug delivery has been demonstrated by in vivo animal experiments and clinical studies, and they are continuing extensively. In this review, the recent research studies, in which the positive outcomes of micelles for ocular targeting of drugs for both anterior and posterior segment diseases as well as glaucoma has been demonstrated by in vitro, ex vivo, or in vivo studies, are highlighted.

A Novel Eye Drop Candidate for Age-Related Macular Degeneration Treatment: Studies on its Pharmacokinetics and Distribution in Rats and Rabbits

Age-related macular degeneration (AMD) is wearing down of macula of retina, causing a blur or loss of vision in the center of the visual field. It can be categorized into dry or wet AMD. Until now, medical treatments for dry AMD have not been developed yet. The aim of this study was to evaluate pharmacokinetics (PKs) and tissue distribution of CK41016, a novel candidate for dry AMD, after intravenous (IV) or eye drop administration in rats and rabbits. In addition, a simple and sensitive bioanalytical method for CK41016 using ultra performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) was developed. PK parameters were estimated by compartmental analysis using a WinNonlin^® software version 8.1 (a Certara™ company). A PK model of CK41016 was well-described by the two-compartment model. The tissue-to-plasma partition coefficient (Kp) of CK41016 was the highest in the vitreous humor of rats and the cornea of rabbits after eye drop administration. In addition, the Caco-2 cell transporter assay confirmed that CK41016 was not an active substrate for the efflux transporter. In summary, the PKs and tissue distribution of CK41016 were successfully evaluated and investigated whether this drug was a substrate of efflux transporters.

Overcoming the Anatomical and Physiological Barriers in Topical Eye Surface Medication Using a Peptide-Decorated Polymeric Micelle

The sealed anatomical features of the eye and its physiological activity that rapidly removes drugs are called anatomical and physiological barriers, which are the cause of more than 90% of drug loss. This aspect remains a critical issue in eye surface medication. Thus, promoting tissue permeability of drugs as well as prolonging their retention on the eye surface can improve their bioavailability and enhance their therapeutic effects. Thanks to the existence of a negatively charged mucin layer on the eye surface, several peptide-decorated polymeric micelles were prepared to enhance the interaction between the micelle and eye surface, thus prolonging the drug retention on the eye surface and promoting its tissue permeability. Tacrolimus (also known as FK506) is a hydrophobic macrolide immunosuppressant used to treat dry eye syndrome and other eye diseases. However, its hydrophobic nature makes its delivery as a topical eye surface medication difficult, with the risk of side effects due to overdoses. Therefore, the aim of this work is to evaluate the ability of FK506 micelles in promoting their permeability on the eye surface. Our results showed that the positively charged nanomicelles could significantly prolong FK506 retention on the eye surface and enhance its corneal permeability in ex vivo and in vivo conditions. FK506 nanomicelles exhibited superior curing effects against dry eye diseases than the FK506 suspension and a commercial FK506 formula. It exerted better inhibitory effects on eye surface inflammation and corneal epithelium apoptosis when examined by a slip lamp and a transferase-mediated dUTP nick end labeling assay, respectively. Further assays revealed the higher suppressive effects on the expression of several inflammation-related factors at an mRNA and protein level. Hence, our results suggested that these positively charged nanomicelles might be a good drug delivery system for ocular surface medication.

Power Analysis and Sample Size Determination for Crossover Trials with Application to Bioequivalence Assessment of Topical Ophthalmic Drugs Using Serial Sampling Pharmacokinetic Data

OBJECTIVE

To develop methods for determining a suitable sample size for bioequivalence assessment of generic topical ophthalmic drugs using crossover design with serial sampling schemes.

METHODS

The power functions of the Fieller-type confidence interval and the asymptotic confidence interval in crossover designs with serial-sampling data are here derived. Simulation studies were conducted to evaluate the derived power functions.

RESULTS

Simulation studies show that two power functions can provide precise power estimates when normality assumptions are satisfied and yield conservative estimates of power in cases when data are log-normally distributed. The intra-correlation showed a positive correlation with the power of the bioequivalence test. When the expected ratio of the AUCs was less than or equal to 1, the power of the Fieller-type confidence interval was larger than the asymptotic confidence interval. If the expected ratio of the AUCs was larger than 1, the asymptotic confidence interval had greater power. Sample size can be calculated through numerical iteration with the derived power functions.

CONCLUSION

The Fieller-type power function and the asymptotic power function can be used to determine sample sizes of crossover trials for bioequivalence assessment of topical ophthalmic drugs.

Enhancement of Retinal Function and of Neural Conduction Along the Visual Pathway Induced by Treatment with Citicoline Eye Drops in Liposomal Formulation in Open Angle Glaucoma: A Pilot Electrofunctional Study

INTRODUCTION

To evaluate the retinal function and the relative neural conduction along the visual pathway after treatment with citicoline in liposomal formulation (CLF) eye drops in patients with open angle glaucoma (OAG).

METHODS

Twelve OAG patients (mean age ± standard deviation 52.58 ± 11.39 years, intraocular pressure < 18 mmHg under topical hypotensive treatment, Humphrey field analyzer mean deviation - 4.49 ± 2.46 dB) were enrolled. Only one eye of studied patients was treated with CLF eye drops (OMK1-LF^®, Omikron Italia, 3 drops/day) (CLF group, 12 eyes) over a period of 4 months. In CLF eyes, pattern electroretinogram (PERG), visual evoked potentials (VEP), and visual field test were assessed at baseline and at the end of treatment (month 4).

RESULTS

After treatment with CLF eye drops, a significant increase of PERG P50-N95 amplitude and a significant shortening of VEP P100 implicit time were found. In CLF eyes, the shortening of VEP P100 implicit time was significantly correlated with the increase of PERG P50-N95 amplitude.

CONCLUSION

Data from this pilot study suggest that treatment with CLF eye drops induces an enhancement of the retinal bioelectrical responses (increase of PERG amplitude) with a consequent improvement of the bioelectrical activity of the visual cortex (shortening of VEP implicit time).

FUNDING

Omikron Italia S.r.l. and Opko Health Europe.

Co-Delivery of Timolol and Brimonidine with a Polymer Thin-Film Intraocular Device

PURPOSE

We developed a polycaprolactone (PCL) co-delivery implant that achieves zero-order release of 2 ocular hypotensive agents, timolol maleate and brimonidine tartrate. We also demonstrate intraocular pressure (IOP)-lowering effects of the implant for 3 months in vivo.

METHODS

Two PCL thin-film compartments were attached to form a V-shaped co-delivery device using film thicknesses of ∼40 and 20 μm for timolol and brimonidine compartments, respectively. In vitro release kinetics were measured in pH- and temperature-controlled fluid chambers. Empty or drug-loaded devices were implanted intracamerally in normotensive rabbits for up to 13 weeks with weekly measurements of IOP. For ocular concentrations, rabbits were euthanized at 4, 8, or 13 weeks, aqueous fluid was collected, and ocular tissues were dissected. Drug concentrations were measured by liquid chromatography-tandem mass spectrometry.

RESULTS

In vitro studies show zero-order release kinetics for both timolol (1.75 μg/day) and brimonidine (0.48 μg/day) for up to 60 days. In rabbit eyes, the device achieved an average aqueous fluid concentration of 98.1 ± 68.3 ng/mL for timolol and 5.5 ± 3.6 ng/mL for brimonidine. Over 13 weeks, the drug-loaded co-delivery device resulted in a statistically significant cumulative reduction in IOP compared to untreated eyes (P < 0.05) and empty-device eyes (P < 0.05).

CONCLUSIONS

The co-delivery device demonstrated a zero-order release profile in vitro for 2 hypotensive agents over 60 days. In vivo, the device led to significant cumulative IOP reduction of 3.4 ± 1.6 mmHg over 13 weeks. Acceptable ocular tolerance was seen, and systemic drug levels were unmeasurable.

Release of Moxifloxacin From Corneal Collagen Shields

OBJECTIVES

To investigate the diffusion of moxifloxacin through bandage contact lenses (BCLs) versus corneal collagen shields (CSs), the relative ability of BCLs and CSs to release moxifloxacin, and the potential of release of moxifloxacin from CSs in the clinical setting.

METHODS

Using an in vitro model, the diffusion of 5% moxifloxacin across BCLs and CSs was compared. Next, the amount of drug release from BCLs and CSs soaked in 0.5% moxifloxacin was measured. Finally, based on a clinical model, CSs were soaked in Vigamox (commercial moxifloxacin) and the total concentration released was detected. Collagen shields remained intact after 24 hr; therefore, enzymatic digestion and mechanical grinding of the CS were performed to determine whether further drug could be released. The concentration of moxifloxacin was measured using a spectrophotometer at set time points up to 24 hr.

RESULTS

In the diffusion assay, 35.7±10.5% diffused through the BCLs and 36.2±11.8% diffused through the CSs (P=0.77). The absorption assay demonstrated at 120 min, a total of 33.3±6.77 μg/mL was released from BCLs compared with 45.8±5.2 μg/mL from the CSs (P=0.0008). In vitro experiments to simulate clinical application of Vigamox-soaked CS found the concentration of moxifloxacin released of 127.7±7.25 μg/mL in 2 mL of phosphate-buffered saline over 24 hr.

CONCLUSIONS

Moxifloxacin diffuses through BCLs and CSs at similar rates; however, CSs have greater capacity to absorb and release moxifloxacin compared with BCLs. Vigamox-soaked CSs released 250 μg of moxifloxacin and may be a useful method to prevent endophthalmitis.

A microengineered human corneal epithelium-on-a-chip for eye drops mass transport evaluation

Animals are commonly used for pharmacokinetic studies which are the most frequent events tested during ocular drug development and preclinical evaluation. Inaccuracy, cost, and ethical criticism in these tests have created a need to construct an in vitro model for studying corneal constraints. In this work, a porous membrane embedded microfluidic platform is fabricated that separates a chip into an apical and basal side. After functionalizing the membrane surface with fibronectin, the membrane's mechanical and surface properties are measured to ensure correct modeling of in vivo characteristics. Immortalized human corneal epithelial cells are cultured on the membrane to create a microengineered corneal epithelium-on-a-chip (cornea chip) that is validated with experiments designed to test the barrier properties of the human corneal epithelium construct using model drugs. A pulsatile flow model is used that closely mimics the ocular precorneal constraints and is reasonable for permeability analysis that models in vivo conditions. This model can be used for preclinical evaluations of potential therapeutic drugs and to mimic the environment of the human cornea.

Intraocular Penetration of a vNAR: In Vivo and In Vitro VEGF165 Neutralization

Variable new antigen receptor domain (vNAR) antibodies are novel, naturally occurring antibodies that can be isolated from naïve, immune or synthetic shark libraries. These molecules are very interesting to the biotechnology and pharmaceutical industries because of their unique characteristics related to size and tissue penetrability. There have been some approved anti-angiogenic therapies for ophthalmic conditions, not related to vNAR. This includes biologics and chimeric proteins that neutralize vascular endothelial growth factor (VEGF)₁₆₅, which are injected intravitreal, causing discomfort and increasing the possibility of infection. In this paper, we present a vNAR antibody against human recombinant VEGF₁₆₅ (rhVEGF₁₆₅) that was isolated from an immunized Heterodontus francisci shark. A vNAR called V13, neutralizes VEGF₁₆₅ cytokine starting at 75 μg/mL in an in vitro assay based on co-culture of normal human dermal fibroblasts (NHDFs) and green fluorescence protein (GFP)-labeled human umbilical vein endothelial cells (HUVECs) cells. In the oxygen-induced retinopathy model in C57BL/6:Hsd mice, we demonstrate an endothelial cell count decrease. Further, we demonstrate the intraocular penetration after topical administration of 0.1 μg/mL of vNAR V13 by its detection in aqueous humor in New Zealand rabbits with healthy eyes after 3 h of application. These findings demonstrate the potential of topical application of vNAR V13 as a possible new drug candidate for vascular eye diseases.

Absence of a secondary glucocorticoid response in C57BL/6J mice treated with topical dexamethasone

Glucocorticoids such as dexamethasone can cause an increase in intraocular pressure (IOP) in some of the population, but not all. In this paper we used a mouse model of glucocorticoid induced ocular hypertension to examine the changes in the anterior segment of the eye in mice that failed to respond to glucocorticoid treatment with a sustained increase in IOP. C57BL/6J mice were treated with either 0.1% dexamethasone sodium phosphate ophthalmic solution or sterile PBS 3 times daily for up to 5 weeks. IOP was measured weekly at approximately the same time of the day. After 3–5 weeks of treatment, eyes were enucleated and evaluated for changes associated with steroid induced glaucoma. These studies showed that IOP was significantly elevated in dexamethasone (DEX) treated mice compared to PBS treated mice after 3 weeks of treatment, but IOP in DEX treated mice returned to baseline levels after 5 weeks of treatment. All the mice demonstrated a response to the glucocorticoid treatments and showed an elevation in FKBP5 expression after both 3 and 5 weeks of DEX treatment (primary glucocorticoid response protein) and a weight loss. Western blot analysis of anterior segments from treated mice, however, did not show an increase in secondary glucocorticoid response proteins such as β3 integrin or myocilin. Fibronectin levels were also not statistically different. The data suggest that in mice, which do not exhibit a prolonged increase in IOP in response to the DEX treatment, there is a compensatory mechanism that can prevent or turn off the secondary glucocorticoid response.

Rufloxacin Eyedrops: Effect of Different Formulations on Ocular Pharmacokinetics in Rabbits

PURPOSE

To evaluate the aqueous humor pharmacokinetics of rufloxacin in rabbits after topical administration of different formulations, and to individuate the ones showing the best pharmacokinetic profile.

METHODS

Six formulations were instilled in rabbit eyes: two pH 7.2 suspensions of non-salified rufloxacin base, or zwitterion (RUF), one of which was viscosized with tamarind seed polysaccharide (TSP); two pH 7.2 solutions of RUF obtained using hydroxypropyl-beta-cyclodextrin (CD), one of which was viscosized with TSP; and two pH 5.0 solutions of rufloxacin hydrochloride (RUF-HCl ), one of which was viscosized with TSP. At different times after administration, samples of aqueous humor were withdrawn and analyzed by high-pressure liquid chromatography. The main pharmacokinetic parameters of RUF in the aqueous humor produced by the different formulations were calculated and statistical differences were assessed.

RESULTS

The best results, in terms of aqueous humor bioavailability, were observed with two TSP-viscosized formulations: a solution of the hydrochloride (TSP/RUF-HCl) and a suspension of the base (TSP/RUF), followed by the non-viscosized solution of RUF-HCl. The formulations containing CD-solubilized RUF were much less effective.

CONCLUSIONS

The present data confirm the significant availability-enhancing properties of tamarind seed polysaccharide, and indicate that solubilization of RUF with hydroxypropyl-beta-cyclodextrin (CD/RUF) results in decreased drug availability with respect to standard formulations. Two of the TSP-viscosized formulations (RUF suspension and RUF-HCl solution) produced aqueous humor RUF concentrations in the range of activity against Enterobacteriaceae and Pseudomonas aeruginosa, thus warranting further studies on applications of rufloxacin in ocular therapy.

Nanoparticles for drug delivery to the anterior segment of the eye

Commercially available ocular drug delivery systems are effective but less efficacious to manage diseases/disorders of the anterior segment of the eye. Recent advances in nanotechnology and molecular biology offer a great opportunity for efficacious ocular drug delivery for the treatments of anterior segment diseases/disorders. Nanoparticles have been designed for preparing eye drops or injectable solutions to surmount ocular obstacles faced after administration. Better drug pharmacokinetics, pharmacodynamics, non-specific toxicity, immunogenicity, and biorecognition can be achieved to improve drug efficacy when drugs are loaded in the nanoparticles. Despite the fact that a number of review articles have been published at various points in the past regarding nanoparticles for drug delivery, there is not a review yet focusing on the development of nanoparticles for ocular drug delivery to the anterior segment of the eye. This review fills in the gap and summarizes the development of nanoparticles as drug carriers for improving the penetration and bioavailability of drugs to the anterior segment of the eye.

Topical Ocular Delivery of TGF-β1 to the Back of the Eye: Implications in Age-Related Neurodegenerative Diseases

Dysregulation of the transforming growth factor-β1 (TGF-β1)/selected small mother against decapentaplegic (SMAD) pathway can be implicated in development of age-related macular degeneration (AMD), and the delivery of TGF-β1 could be beneficial for AMD. We developed a new ophthalmic formulation of TGF-β1 assessing the ocular pharmacokinetic profile of TGF-β1 in the rabbit eye. Small unilamellar vesicles (SUV) loaded with TGF-β1 were complemented with Annexin V and Ca²⁺, and the vitreous bioavailability of TGF-β1 was assessed after topical ocular administration by a commercial ELISA kit. We detected high levels of TGF-β1 (C_max 114.7 ± 12.40 pg/mL) in the vitreous after 60 min (T_max) from the topical application of the liposomal suspension. Ocular tolerability was also assessed by a modified Draize’s test. The new formulation was well tolerated. In conclusion, we demonstrated that the novel formulation was able to deliver remarkable levels of TGF-β1 into the back of the eye after topical administration. Indeed, this TGF-β1 delivery system may be useful in clinical practice to manage ophthalmic conditions such as age-related macular degeneration, skipping invasive intraocular injections.

Multifunctional organic-inorganic hybrid nanoparticles and nanosheets based on chitosan derivative and layered double hydroxide: cellular uptake mechanism and application for topical ocular drug delivery

To study the cellular uptake mechanism of multifunctional organic-inorganic hybrid nanoparticles and nanosheets, new chitosan-glutathione-valine-valine-layered double hydroxide (CG-VV-LDH) nanosheets with active targeting to peptide transporter-1 (PepT-1) were prepared, characterized and further compared with CG-VV-LDH nanoparticles. Both organic-inorganic hybrid nanoparticles and nanosheets showed a sustained release in vitro and prolonged precorneal retention time in vivo, but CG-VV-LDH nanoparticles showed superior permeability in the isolated cornea of rabbits than CG-VV-LDH nanosheets. Furthermore, results of cellular uptake on human corneal epithelial primary cells (HCEpiC) and retinal pigment epithelial (ARPE-19) cells indicated that both clathrin-mediated endocytosis and active transport of PepT-1 are involved in the internalization of CG-VV-LDH nanoparticles and CG-VV-LDH nanosheets. In summary, the CG-VV-LDH nanoparticle may be a promising carrier as a topical ocular drug delivery system for the treatment of ocular diseases of mid-posterior segments, while the CG-VV-LDH nanosheet may be suitable for the treatment of ocular surface diseases.

Atropine Eye Drops: A Proposed Field Expedient Substitute in the Absence of Atropine Autoinjectors

Nerve agents are a threat to military and civilian health. The antidote, atropine sulfate, is delivered by autoinjector, which is a limited resource. We propose the use of 1% atropine ophthalmic solution (supplied commercially in 5mL or 15 mL bottles) via oral, ocular, and intranasal administration as an expedient substitute in austere environments.

In vitro, ex vivo and in vivo characterization of PLGA nanoparticles loading pranoprofen for ocular administration

Pranoprofen (PF) is a NSAID considered as a safe anti-inflammatory treatment for strabismus and/or cataract surgery. The drug has been formulated in poly (lactic/glycolic) acid (PLGA) nanoparticles (PF-F1NPs with cPF 1.5mg/mL, PF-F2NPs with cPF 1mg/mL) produced by solvent displacement technique and tested the in vitro cytotoxicity, ex vivo corneal permeation, in vivo ocular tolerance and in vivo anti-inflammatory efficacy of PF-F1NPs, PF-F2NPs, in comparison to eye drops conventional dosage form (Oftalar(®), PF 1mg/mL) and free drug solution (PF dissolved in PBS, 1.5mg/mL). The mean particle size of both formulations was around 350nm, with polydispersity index below 0.1, and a net negative charge of -7.41mV and -8.5mV for PF-F1NPs and PF-F2NPs, respectively. Y-79 human retinoblastoma cell line was used to evaluate the cytotoxicity of PF-F1NPs and PF-F2NPs, which were compared to blank NPs and free drug solution (PF dissolved in PBS, 1.5mg/mL). Concentrations up to 75μg/mL exhibited no toxicity to Y-79 cells, whereas at 150μg/mL a decrease of about 80% on the cell viability was observed after exposing the cells to PF-F1NPs. When treating the Y-79 cells with concentrations of PF-F2NPs between 1μg/mL to 100μg/mL, the cell viability was similar to control values after 24h and 48h of exposure. An ex vivo corneal permeation study was carried out in New Zealand rabbits. A very similar profile has been observed for the permeation of PF through the cornea when administered as eye drops and as free drug solution, which was kept much lower in comparison to PF-NPs formulations. The permeated amount of PF from the PF-F1NPs was slightly smaller than from PF-F2NPs, attributed to the increase of viscosity of the formulations with the increase of cPVA concentration. New Zealand white rabbits were also used to evaluate the irritancy of PF-F1NPs and PF-F2NPs, which demonstrated to be well-tolerated to the eye (i.e. the mean total score (MTS) was 0). PF-F2NPs exhibited the highest QP (amounts of PF permeated in the cornea) and significantly reduced the ocular edema compared to the tested formulations. The QR (amounts of PF retained in the cornea) of the PF-F1NPs was greater than that obtained for PF-F2NPs.

An Exploratory Microdialysis Study to Assess the Ocular Pharmacokinetics of Ciprofloxacin Eye Drops in Rabbits

PURPOSE

Despite the high frequency of use, data regarding the ocular in vivo pharmacokinetics (PK) of topically applied antibiotics are sparse. This study seeks to investigate the PK of the widely used fluoroquinolone ciprofloxacin by means of in vivo microdialysis.

METHODS

Twelve New Zealand white rabbits were included in the experiments. Under general anesthesia, microdialysis probes were implanted in the anterior chamber and the posterior segment of the same eye. After a period of 90 min after implantation, one drop of ciprofloxacin was administered onto the ocular surface. Microdialysis samples of the anterior chamber and the vitreous were collected every 30 min for 6 h. Relative recovery was assessed by retrodialysis to calculate absolute concentration values. Samples were analyzed using HPLC.

RESULTS

In the anterior chamber, the maximum total drug concentration (Cmax) amounted to 0.373 ± 0.281 μg/mL and was reached (Tmax) after 116 ± 36 min. Calculated area under the concentration-time curve AUC(0-n) for ciprofloxacin in the anterior chamber was 78.8 ± 47.1 μg min/mL. For the vitreous, Cmax was 0.02 ± 0.03 μg/mL and maximum drug concentration was reached 107 ± 60 min after topical administration. AUC(0-n) for ciprofloxacin in the vitreous was 0.269 ± 0.370 μg min/mL.

CONCLUSION

Microdialysis is a suitable method to assess in vivo pharmacokinetic profiles in the anterior chamber and in the vitreous. In the anterior chamber, maximum drug concentration was reached ∼2 h after single drug administration. Although the drug concentration in the vitreous was considerably lower, time course of drug concentration was comparable.

The antibacterial activity of levofloxacin eye drops against staphylococci using an in vitro pharmacokinetic model in the bulbar conjunctiva

The incidence of fluoroquinolone-resistant staphylococcal isolates from the conjunctival sac is increasing. We compared pharmacological effects of levofloxacin (LVFX) against Staphylococcus epidermidis using an in vitro pharmacokinetic (PK) model simulating the concentration in the bulbar conjunctiva after applying eye drops of 0.5% and 1.5% LVFX. We used S. epidermidis conjunctival sac isolates [minimum inhibitory concentrations (MICs) of LVFX, 0.125 μg/mL]. LVFX-resistant strains were obtained from parental strains after culture with LVFX. The in vitro PK model simulated the concentration in the bulbar conjunctiva following three topical applications of 0.5% or 1.5% LVFX ophthalmic solution (0, 4, and 8 h) to rabbit eyes. Parental and LVFX-resistant strains were exposed to LVFX in the in vitro PK model, and changes in viable bacterial counts were evaluated for 12 h. The MICs of LVFX for the resistant isolates were 2-32 times higher than the parental strain, and those with MICs ≥2 ug/mL had mutations in the quinolone resistance-determining region. The PK model simulation predicts that 1.5% LVFX exerts bactericidal and bacteriostatic effects against strains with MICs of 0.125-2 and 4 μg/mL, respectively, whereas 0.5% LVFX would only be effective against strains with MICs of 0.125-1 μg/mL. The PK model predicts that the 1.5% LVFX ophthalmic solution exhibits a stronger bactericidal effect against resistant staphylococci in the bulbar conjunctiva than the 0.5% LVFX ophthalmic solution.

Prophylactic Vancomycin Drops Reduce the Severity of Early Bacterial Keratitis in Keratoprosthesis

BACKGROUND

Artificial cornea transplantation, keratoprosthesis, improves vision for patients at high risk of failure with human cadaveric cornea. However, post-operative infection can cause visual loss and implant extrusion in 3.2-17% of eyes. Long-term vancomycin drops are recommended following keratoprosthesis to prevent bacterial keratitis. Evidence, though, in support of this practice is poor. We investigated whether prophylactic vancomycin drops prevented bacterial keratitis in an animal keratoprosthesis model.

METHODOLOGY

Twenty-three rabbits were assigned either to a prophylactic group (n = 13) that received vancomycin 1.4% drops 5 times/day from keratoprosthesis implantation to sacrifice, or a non-prophylactic group (n = 10) that received no drops. All rabbits had Staphylococcus aureus inoculation into the cornea at 7-12 days post-implantation and were sacrificed at predetermined time-points. Prophylactic and non-prophylactic groups were compared with slit-lamp photography (SLP), anterior segment optical coherence tomography (AS-OCT), and histology, immunohistochemistry and bacterial quantification of excised corneas. Corneal vancomycin pharmacokinetics were studied in 8 additional rabbits.

RESULTS

On day 1 post-inoculation, the median SLP score and mean±SEM AS-OCT corneal thickness (CT) were greater in the non-prophylactic than the prophylactic group (11 vs. 1, p = 0.049 and 486.9±61.2 vs. 327.4±37.1 μm, p = 0.029 respectively). On days 2 and 4, SLP scores and CT were not significantly different. Immunohistochemistry showed a greater CD11b+ve/non-CD11b+ve cell ratio in the non-prophylactic group (1.45 vs. 0.71) on day 2. Bacterial counts were not significantly different between the two groups. Corneal vancomycin concentration (2.835±0.383 μg/ml) exceeded minimum inhibitory concentration (MIC) for Staphylococcus aureus only after 16 days of vancomycin drops. Two of 3 rabbits still developed infection despite bacterial inoculation after 16 days of prophylactic drops.

CONCLUSIONS

Prophylactic vancomycin drops provided short-term benefit, but did not prevent infection. Achieving MIC in the cornea was not sufficient to prevent Staphylococcus aureus keratitis. Patients should continue to be counselled regarding the risk of infection following keratoprosthesis.

Ripasudil: first global approval

Ripasudil hydrochloride hydrate (Glanatec® ophthalmic solution 0.4 %; hereafter referred to as ripasudil) is a small-molecule, Rho-associated kinase inhibitor developed by Kowa Company, Ltd. for the treatment of glaucoma and ocular hypertension. This compound, which was originally discovered by D. Western Therapeutics Institute, Inc., reduces intraocular pressure (IOP) by directly acting on the trabecular meshwork, thereby increasing conventional outflow through the Schlemm's canal. As a result of this mechanism of action, ripasudil may offer additive effects in the treatment of glaucoma and ocular hypertension when used in combination with agents such as prostaglandin analogues (which increase uveoscleral outflow) and β blockers (which reduce aqueous production). The eye drop product has been approved in Japan for the twice-daily treatment of glaucoma and ocular hypertension, when other therapeutic agents are not effective or cannot be administered. Phase II study is underway for the treatment of diabetic retinopathy. This article summarises the milestones in the development of ripasudil leading to the first approval for glaucoma and ocular hypertension.

Delivery of Topically Applied Calpain Inhibitory Peptide to the Posterior Segment of the Rat Eye

We developed an inhibitory peptide that specifically acts against mitochondrial μ-calpain (Tat-μCL, 23 amino acid, 2857.37 Da) and protects photoreceptors in retinal dystrophic rats. In the present study, we topically administered Tat-μCL to the eyes of Sprague-Dawley rats for 7 days to determine both the delivery route of the peptide to the posterior segment of the eye and the kinetics after topical application in adult rats. Distribution of the peptide was determined by immunohistochemical analysis, and enzyme-linked immune-absorbent assay was used to quantify the accumulation in the retina. Peptides were prominently detected in both the anterior and posterior segments of the eye at 1 h after the final eye drop application. Immunohistochemically positive reactions were observed in the retina, optic nerve, choroid, sclera and the retrobulbar tissues, even in the posterior portion of the eye. Immunoactivities gradually diminished at 3 and 6 h after the final eye drop. Quantitative estimations of the amount of peptide in the retina were 15.3, 5.8 and 1.0 pg/μg protein at 1, 3 and 6 h after the final instillation, respectively. Current results suggest that while the topically applied Tat-μCL peptide reaches the posterior segment of the retina and the optic nerve, the sufficient concentration (> IC50) is maintained for at least 6 h in the rat retina. Our findings suggest that delivery of topically applied peptide to the posterior segment and optic nerve occurs through the conjunctiva, periocular connective tissue, sclera and optic nerve sheath.

Ocular hypotensive safety and systemic absorption of AR-13324 ophthalmic solution in normal volunteers

PURPOSE

To evaluate the ocular and systemic safety and systemic absorption of AR-13324 in normotensive, healthy volunteers.

DESIGN

Open-label, noncomparative, single-arm phase 1 clinical trial.

METHODS

setting: Phase 1 clinical trials unit. patient or study population: Eighteen normal adult volunteers. intervention or observation procedures: Subjects received AR-13324 ophthalmic solution 0.02% once daily in the morning in each eye for 8 days.

MAIN OUTCOME MEASURES

Plasma concentrations of AR-13324 and its presumed human metabolite, AR-13503, and ocular safety measures.

RESULTS

There were no observed plasma AR-13324 concentrations higher than the lower limit of quantitation at any time point in any subject. Only 1 plasma sample from 1 subject (day 8 at 8 hours after dose administration) had an AR-13503 concentration higher than the lower limit of quantitation (0.11 ng/mL). AR-13324 dosed once daily in the morning produced substantial reductions in baseline intraocular pressure of up to 6 mm Hg that were statistically significant (P < .001) at all time points after dose administration. All but 1 subject exhibited transient conjunctival hyperemia to some degree in the 8-hour period after morning dosing.

CONCLUSIONS

AR-13324 ophthalmic solution 0.2%, administered once daily in the morning for 8 days, produced little or no quantifiable systemic exposure to the parent compound or a presumed metabolite. Clinically and statistically significant reductions in intraocular pressure were observed in these normotensive subjects that were more pronounced compared with what has been observed commonly with other ocular hypotensive therapies in this population.

[Progression of drug delivery system for glaucoma]

Reduction of intraocular pressure (IOP) by drugs is a major treatment for glaucoma. Clinically, diverse antiglaucoma drugs take effect to decrease the IOP through different mechanisms.However, due to limitations of traditional form of eye drops, the bioavailability of the drug and the patient compliance is lowered, the clinical efficacy is not good and also some toxic and side-effects come out.Otherwise, traditional medication is not suitable for neuroprotective drugs to work on both retina and optic nerve. Drug delivery system has the potential to improve the bioavailability of the drug, prolong the time of drug action, decrease the dosage and frequency of drugs, reduce the side-effects, and improve the patient compliance and efficacy.It is one of the most important studies in glaucoma medication development because it is valuable for patients' neuroprotection.Nowadays, several novel delivery systems have been designed. This review will focus on the progressions of some of the sustained-release antiglaucoma eye drops, polymeric gels, colloidal systems, membrane-controlled drug delivery system, ocular implants, and transscleral drug delivery systems.

[Transcorneal drug delivery: prospects for the use of liposomes]

Anatomical and physiological ocular surface barriers are responsible for low bioavailability of topical ophthalmic drugs. The unique structure of the cornea, epithelial cells and hydrophilic stroma in particular, impedes permeation of hydro- and lipophilic drugs via common routs of administration. The tear film with its proteins and enzymes also acts as a barrier. Despite several corneal transporters that take part in permeation of some drugs, increasing bioavailability of ophthalmic drugs in general remains a question of current importance. Liposomes are an option. These vesicular structures consist of the outer lipid bilayer and the inner aqueous compartment, which can be filled with a medication solution. This peculiarity of liposomes ensures their penetration through both hydro- and lipophilic mediums of the eye, including the barriers of the anterior and posterior segments. Liposomes are effective means of vectored drug delivery into the anterior chamber. This paper presents a review of the current knowledge on the interaction of drugs and ocular surface barriers as well as the prospects for the use of liposomes for transcorneal drug delivery.

A novel nanoscale-dispersed eye ointment for the treatment of dry eye disease

A novel nanoscale-dispersed eye ointment (NDEO) for the treatment of severe evaporative dry eye has been successfully developed. The excipients used as semisolid lipids were petrolatum and lanolin, as used in conventional eye ointment, which were coupled with medium-chain triglycerides (MCT) as a liquid lipid; both phases were then dispersed in polyvinyl pyrrolidone solution to form a nanodispersion. Single-factor experiments were conducted to optimize the formulations. A transmission electron micrograph showed that the ointment matrix was entrapped in the nanoemulsion of MCT, with a mean particle size of about 100 nm. The optimized formulation of NDEO was stable when stored for six months at 4 °C, and demonstrated no cytotoxicity to human corneal epithelial cells when compared with commercial polymer-based artificial tears (Tears Natural Forte). The therapeutic effects of NDEO were evaluated on a mouse model with 'dry eye'. Both the tear break-up time and fluorescein staining demonstrated therapeutic improvement, displaying a trend of positive correlation with higher concentrations of ointment matrix in the NDEO formulations compared to a marketed product. Histological evaluation demonstrated that the NDEO restored the normal corneal and conjunctival morphology and is safe for ophthalmic application.

Ultrasound-enhanced delivery of antibiotics and anti-inflammatory drugs into the eye

Delivery of sufficient amounts of therapeutic drugs into the eye is often a challenging task. In this study, ultrasound application (frequencies of 400 KHz to 1 MHz, intensities of 0.3-1.0 W/cm(2) and exposure duration of 5 min) was investigated to overcome the barrier properties of cornea, which is a typical route for topical administration of ophthalmic drugs. Permeability of ophthalmic drugs, tobramycin and dexamethasone and sodium fluorescein, a drug-mimicking compound, was studied in ultrasound- and sham-treated rabbit corneas in vitro using a standard diffusion cell setup. Light microscopy observations were used to determine ultrasound-induced structural changes in the cornea. For tobramycin, an increase in permeability for ultrasound- and sham-treated corneas was not statistically significant. Increase of 46%-126% and 32%-109% in corneal permeability was observed for sodium fluorescein and dexamethasone, respectively, with statistical significance (p < 0.05) achieved at all treatment parameter combinations (compared with sham treatments) except for 1-MHz ultrasound applications for dexamethasone experiments. This permeability increase was highest at 400 kHz and appeared to be higher at higher intensities applied. Histologic analysis showed structural changes that were limited to epithelial layers of cornea. In summary, ultrasound application provided enhancement of drug delivery, increasing the permeability of the cornea for the anti-inflammatory ocular drug dexamethasone. Future investigations are needed to determine the effectiveness and safety of this application in in vivo long-term survival studies.

Bovine corneal epithelial primary cultures as an in vitro model for ophthalmic drugs studies

In the recent years a significant development of investigations with regard to bioavailability of ocular drugs has been noticed. The corneal epithelial barrier is the main pathway for ocular penetration of topically applied ophthalmic drugs into the anterior chamber. To work out an in vitro model of bovine corneal epithelial primary cultures and exercise it for permeability research with lipophilic and hydrophilic markers, permeability coefficients estimation of the 6-carboxyfluorescein and rhodamin B was made. The corneal epithelial cultures of the 3th or 4th passage were chosen for layered culture with inserts based on the liquid-liquid interface (for the first week) and the air-liquid interface (for the two following weeks). On the 7th, 12th, 18th, 21st experiment day TER values, and on the 21st day drug permeability coefficients, were determined. The mean TER values of the 7th, 12th, 18th, 21st day of corneal epithelial culture were: 122.14, 155.14, 198.43 and; 247.43 Wcm2, respectively. The mean values of permeability coefficients on the 21st day of culture for 6-carboxyfluorescein and rhodamin B were 3.87 +/-0.10 x 10(-6)cm/s and 3.65 +/- 0.06 x 10(-6)cm/s, respectively. We state that the in vitro bovine corneal epithelial primary culture model is useful for ocular studies.

Effect of PF-04217329 a prodrug of a selective prostaglandin EP(2) agonist on intraocular pressure in preclinical models of glaucoma

Better control of intraocular pressure (IOP) is the most effective way to preserve visual field function in glaucomatous patients. While prostaglandin FP analogs are leading the therapeutic intervention for glaucoma, new target classes also are being identified with new lead compounds being developed for IOP reduction. One target class currently being investigated includes the prostaglandin EP receptor agonists. Recently PF-04217329 (Taprenepag isopropyl), a prodrug of CP-544326 (active acid metabolite), a potent and selective EP(2) receptor agonist, was successfully evaluated for its ocular hypotensive activity in a clinical study involving patients with primary open angle glaucoma. In the current manuscript, the preclinical attributes of CP-544326 and PF-0421329 have been described. CP-544326 was found to be a potent and selective EP(2) agonist (IC(50) = 10 nM; EC(50) = 2.8 nM) whose corneal permeability and ocular bioavailability were significantly increased when the compound was dosed as the isopropyl ester prodrug, PF-04217329. Topical ocular dosing of PF-04217329 was well tolerated in preclinical species and caused an elevation of cAMP in aqueous humor/iris-ciliary body indicative of in vivo EP(2) target receptor activation. Topical ocular dosing of PF-04217329 resulted in ocular exposure of CP-544326 at levels greater than the EC(50) for the EP(2) receptor. PF-04217329 when dosed once daily caused between 30 and 50% IOP reduction in single day studies in normotensive Dutch-belted rabbits, normotensive dogs, and laser-induced ocular hypertensive cynomolgus monkeys and 20-40% IOP reduction in multiple day studies compared to vehicle-dosed eyes. IOP reduction was sustained from 6 h through 24 h following a single topical dose. In conclusion, preclinical data generated thus far appear to support the clinical development of PF-04217329 as a novel compound for the treatment of glaucoma.

[Preparation and lacrimal pharmacokinetics of eye drops of puerarin liposomes in rabbit tears]

OBJECTIVE

To prepare eye drops of puerarin liposomes and investigate its lacrimal pharmacokinetics in rabbit tears.

METHOD

Puerarin liposomes were prepared by reverse phase evaporation technique. The liposomes and free puerarin were separated by SephadexG-50 chromatography and then encapsulation ratio of liposomes was determined in detail. Micromorphology of liposome particles was observed by electronic transmission microscope and the size distribution of the liposomes was analyzed by laser particle size analyzer. The concentration of puerarin in rabbit's tears was determined by HPLC after ocular administration of 50 microL puerarin liposomes while puerarin eye drops was chosen as control with the same puerarin concentration. The pharmacokinetic parameters were calculated by software program 3P97 according to one-compartment mode.

RESULT

Global liposome nanoparticles with diameter of about 195.7 nm were prepared successfully. The encapsulation ratio of puerarin in the liposomes was 48.3%. The mean residence time (MRT) value and the area under concentration (AUC) of puerarin in liposome were 3.89 and 3.06 times more than those of puerarin eye drops.

CONCLUSION

Liposomes as a drug carrier can greatly increase the concentration of puerarin in tears, enhance the pre-ocular retention time than that of eye drops.

Besifloxacin ophthalmic suspension for bacterial conjunctivitis

Besifloxacin hydrochloride ophthalmic suspension 0.6% (Besivance) is a recently approved fluoroquinolone for the topical treatment of bacterial conjunctivitis. The drug is rapidly bactericidal against common bacterial pathogens causing conjunctivitis, i.e., coagulase-negative Staphylococcus, Streptococcus pneumoniae, Staphylococcus aureus and Haemophilus influenzae as well as against other less common organisms. In addition to being a potent agent against Gram-positive and Gram-negative pathogens including those resistant to other fluoroquinolones, besifloxacin has balanced DNA gyrase and topoisomerase IV activity, which should slow the development of resistance. Topical administration achieves high sustained concentrations in human tears and good ocular tissue penetration in animals while demonstrating an excellent safety profile. Besifloxacin's pharmacokinetic and pharmacodynamic characteristics meet the criteria for successful eradication of many Gram-positive and Gram-negative bacteria while demonstrating minimal systemic exposure. The biochemical properties, achievement of target pharmacokinetic/pharmacodynamic goals and the restriction of besifloxacin to topical ophthalmic use should result in slower development of bacterial resistance, making besifloxacin a new, appealing option for empiric therapy in acute bacterial conjunctivitis.

A Mathematical Model for Ocular Tear and Solute Balance

PURPOSE

In this paper we develop a mathematical model that can predict the steady-state tear film thickness and the dynamic tear film thickness and the solute concentration after instillation of a solute-laden fluid in the eye.

METHODS

The mathematical model developed in this paper is based on a balance between the inflow and outflow of tears into the tear film. It incorporates a tear drainage model and a model that relates the tear film thickness to the meniscus radius of curvature. To predict the solute concentrations, the tear balance is coupled with the solute balance. The differential equations for the unsteady balances are solved numerically.

RESULTS

The model predicts that the tear film thickness depends on a number of physiological factors, such as rates of tear production and evaporation, geometry and modulus of the canaliculi, and surface tension and viscosity of tears, and varies from about 3 to 15 microm. The model also predicts that the drainage time for an instilled volume of 15 microl is 1283 s. Additionally, the time required for the tracer concentration to decay to 1% of the value immediately after instillation of a drug-laden 40 microl drop is about 2480 s. Similarly, the time for intensity decay for a radioactive tracer after 25 microl instillation is about 1566 s. Also, the model predicts that the fraction of the instilled drug that reaches the cornea is about 1.3% for topical application of timolol.

CONCLUSIONS

The predicted results agree reasonably with the reported experimental results, at least qualitatively. The model developed here can serve as a useful tool to develop a more precise understanding of various issues related to tears and also evaluate the effect of various parameters on the tear volume.

Effect of Gatifloxacin Ophthalmic Solution 0.3% on Human Corneal Endothelial Cell Density and Aqueous Humor Gatifloxacin Concentration

PURPOSE

To evaluate the effect of gatifloxacin ophthalmic solution 0.3% (Zymar, Allergan, Inc., Irvine, CA, USA) on corneal endothelial cell density and morphology and to measure gatifloxacin penetration into aqueous humor.

METHODS

This was a single-center, open-label clinical study. Ten patients undergoing standard cataract surgery and 20 nonsurgical subjects instilled gatifloxacin 0.3% four times per day for 2 days, then every 10 min for 1 hr on the third day (the surgery day for the cataract patients). Corneal endothelial cells were counted using noncontact specular microscopy. Anterior chamber fluid was withdrawn from the surgical patients, and the gatifloxacin concentration was quantified by high-pressure liquid chromatography.

RESULTS

Baseline endothelial cell counts (mean +/- SD) were 2400 +/- 442 in the surgical group and 2520 +/- 212 in the nonsurgical group. The mean differences from baseline 1 hr after the last dose of gatifloxacin 0.3% were -51 +/- 213 (p = 0.23) in the surgical group and -7 +/- 150 (p = 0.42) in the nonsurgical group. In the nonsurgical group, the mean difference from baseline 3 weeks after the last dose was 18 +/- 147 (p = 0.71). The mean concentration (+/- SD) of gatifloxacin in aqueous humor was 1.26 +/- 0.55 microg/ml.

CONCLUSIONS

A preoperative, prophylactic course of gatifloxacin 0.3% ophthalmic solution did not significantly affect endothelial cell density or morphology, while meaningful drug concentration was achieved in the aqueous humor.

Conjunctival tissue pharmacokinetic properties of topical azithromycin 1% and moxifloxacin 0.5% ophthalmic solutions: a single-dose, randomized, open-label, active-controlled trial in healthy adult volunteers

BACKGROUND

Effective ocular tissue concentrations and prolonged residence times of antibacterial agents are important in treating both acute and chronic diseases. Conjunctival biopsy allows the determination of specific tissue concentration data for topical ophthalmic agents. Drug concentration analysis at various time points following instillation allows interpretation of the residence time and a rationale for dosing frequency.

OBJECTIVE

This study compared the pharmacokinetic parameters of 2 currently available topical ocular antibiotics-azithromycin ophthalmic solution 1% and moxifloxacin ophthalmic solution 0.5%-in the conjunctiva of healthy volunteers after a single topical administration.

METHODS

This single-dose, randomized, open-label, active-controlled clinical trial was conducted at ORA Clinical Research and Development, North Andover, Massachusetts. Subjects were randomly assigned to receive a single dose of azithromycin or moxifloxacin and to undergo biopsy sampling at 30 minutes or 2, 12, or 24 hours after administration. Concentrations of azithromycin and moxifloxacin were determined using liquid chromatography tandem mass spectrometry. Adverse events (AEs) were assessed at all visits using visual acuity measurements, slit-lamp biomicroscopy, and direct questioning.

RESULTS

Forty-eight subjects (mean age, 40.0 years; 48% female; 96% white, 2% black, and 2% Asian) underwent conjunctival biopsy. Mean (SD) concentrations of azithromycin in conjunctival tissue (lower limit of quantitation [LLOQ], 1 microg/g for 1-mg biopsy specimen) were 131 (89), 59 (19), 48 (24), and 32 (20) microg/g at 30 minutes and 2, 12, and 24 hours, respectively (median values, 117, 69, 46, and 30 microg/g). Mean concentrations concentrations of moxifloxacin in conjunctival tissue (LLOQ, 0.05 microg/g for 1-mg biopsy sample) were 1.92 (2.03), 3.77 (8.98), 0.02 (0.04), and 0.01 (0.02) microg/g at 30 minutes and 2, 12, and 24 hours, respectively (median values, 1.12, 0.12, <0.05, and <0.05 microg/g). Thirteen subjects (6 in the azithromycin group and 7 in the moxifloxacin group) experienced 20 AEs, 11 of which were considered possibly related to study treatment, and 15 of which were ocular (most commonly conjunctival hemorrhage).

CONCLUSIONS

In this single-dose study of 2 currently available topical ocular antibiotics in healthy volunteers, therapeutic concentrations were achieved with both agents. Both treatments were well tolerated in the population studied. Clinical Trials Identification Number: NCT00564447.

Polyoxyethylated nonionic surfactants and their applications in topical ocular drug delivery

Topical dosing of ophthalmic drugs to the eye is a widely accepted route of administration because of convenience, ease of use, and non-invasiveness. However, it has been well recognized that topical ocular delivery endures a low bioavailability due to the anatomical and physiological constraints of the eye which limit drug absorption from the pre-corneal surface. Nonionic surfactants as versatile functional agents in topical ocular drug delivery systems are uniquely suited to meet the challenges through their potential ability to increase bioavailability by increasing drug solubility, prolonging pre-corneal retention, and enhancing permeability. This review attempts to place in perspective the importance of polyoxyethylated nonionic surfactants in the design and development of topical ocular drug delivery systems by assessing their compatibility with common ophthalmic inactive ingredients, their impact on product stability, and their roles in facilitating ocular drugs to reach the target sites.

Calculation of AQCmax: comparison of five ophthalmic fluoroquinolone solutions*

ABSTRACT Objective: Ocular tissue penetration of five different ophthalmic fluoroquinolone solutions in the rabbit eye was measured and evaluated by an index of the maximum aqueous concentration (AQCmax).

METHODS

Moxifloxacin 0.5% (MFLX), levofloxacin 0.5% (LVFX), gatifloxacin 0.3% (GFLX), ofloxacin 0.3% (OFLX), or tosufloxacin tosilate 0.3% (TFLX) were instilled into the eyes of white rabbits every 15 min for a total of three doses. Aqueous humor, cornea, iris/ciliary body and vitreous body were collected 10 to 240 min after instillation and drug concentrations were measured by high-performance liquid chromatography.

RESULTS

The concentration of MFLX was the highest in each tissue, with maximum concentrations of MFLX in the aqueous humor (10.16 +/- 1.59 microg/mL) at 30 min after instillation, cornea (156.07 +/- 95.97 microg/g) and iris/ciliary body (11.92 +/- 4.00 microg/g) at 10 min after instillation, and vitreous body (0.099 +/- 0.033 microg/mL) at 30 min after instillation. The concentration of TFLX was the lowest in each tissue, with LVFX, GFLX, and OFLX sharing the mid-ranks. AQCmax : MIC(90) ratio for S. aureus was 150.67 for MFLX, 10.6 for LVFX, 9.69 for GFLX, 3.48 for OFLX, and could not be determined for TFLX.

CONCLUSION

AQCmax is a useful pharmacokinetic parameter for determining the therapeutic efficacy of an ophthalmic antibiotic, especially when combined with MIC(90) values for intraocular pathogens. C(max) of MFLX ophthalmic solution was superior in all tissues (cornea, aqueous humor, iris/ciliary body and vitreous body) among the five ophthalmic solutions studied, exceeding the MIC(90) of S. aureus in all tissues, and MIC(90)s of S. epidermidis, B. cereus, and P. acnes in aqueous humor, cornea, and iris/ciliary body. AQCmax was approximately proportional to C(max) in iris/ciliary body and vitreous, and may be used in combination with MIC(90)s as an index to predict the most appropriate dose and frequency of ophthalmic antibiotics in conjunction with other PK/PD parameters. This study may provide the groundwork for calculation of AQCmax in humans.

Pharmacokinetics, efficacy and safety profiles of preserved and preservative-free tafluprost in healthy volunteers

PURPOSE

Prostanoid F(2alpha) (PF(2alpha)) analogues are commonly used as first-line treatment of glaucoma. Tafluprost is a newly synthesized PF(2alpha) derivative and represents the first PF(2alpha) analogue with a fully preservative-free formulation.

METHODS

A randomized, investigator-masked, single-centre, crossover phase I study evaluated the pharmacokinetics, efficacy and safety profiles of preserved and preservative-free tafluprost 0.0015% eyedrops in healthy volunteers. Both formulations were administered once/day for 8 days each. Plasma concentrations and, consequently, area under the curve (AUC(0-last)), maximum concentration (C(max)) and time to maximum concentration (t(max)) were determined for tafluprost acid, the biologically active metabolite. Intraocular pressure, adverse events, and ocular and systemic safety parameters were analysed.

RESULTS

There were no statistically significant differences in pharmacokinetic parameters between preserved and preservative-free formulations after either single (day 1) or repeated (day 8) dosing. The mean (+/- standard deviation) results for preserved and preservative-free formulations on day 8 were, respectively: AUC(0-last) 581.1 +/- 529.9 pg/min/ml versus 431.9 +/- 457.8 pg/min/ml (p = 0.462); C(max) 31.4 +/- 19.5 pg/ml versus 26.6 +/- 18.0 pg/ml (p = 0.294), and median (range) t(max) 10 (5-15) for both. Generally, plasma concentrations of tafluprost acid were low at all time-points and were cleared rapidly from the circulatory system. There were no unexpected safety findings. The incidence of ocular hyperaemia was similar in both formulations and was of predominantly moderate severity with preserved tafluprost and mild severity with preservative-free tafluprost.

CONCLUSIONS

Preservative-free tafluprost appeared to have similar pharmacokinetic properties to the preserved formulation and was generally well tolerated.