Ocular Tissue Concentrations Research Articles

The Therapeutic Trip of Melatonin Eye Drops: From the Ocular Surface to the Retina.

Melatonin is a ubiquitous molecule found in living organisms, ranging from bacteria to plants and mammals. It possesses various properties, partly due to its robust antioxidant nature and partly owed to its specific interaction with melatonin receptors present in almost all tissues. Melatonin regulates different physiological functions and contributes to the homeostasis of the entire organism. In the human eye, a small amount of melatonin is also present, produced by cells in the anterior segment and the posterior pole, including the retina. In the eye, melatonin may provide antioxidant protection along with regulating physiological functions of ocular tissues, including intraocular pressure (IOP). Therefore, it is conceivable that the exogenous topical administration of sufficiently high amounts of melatonin to the eye could be beneficial in several instances: for the treatment of eye pathologies like glaucoma, due to the IOP-lowering and neuroprotection effects of melatonin; for the prevention of other dysfunctions, such as dry eye and refractive defects (cataract and myopia) mainly due to its antioxidant properties; for diabetic retinopathy due to its metabolic influence and neuroprotective effects; for macular degeneration due to the antioxidant and neuroprotective properties; and for uveitis, mostly owing to anti-inflammatory and immunomodulatory properties. This paper reviews the scientific evidence supporting the use of melatonin in different ocular districts. Moreover, it provides data suggesting that the topical administration of melatonin as eye drops is a real possibility, utilizing nanotechnological formulations that could improve its solubility and permeation through the eye. This way, its distribution and concentration in different ocular tissues may support its pleiotropic therapeutic effects.

Thermosensitive In Situ Gelling Poloxamers/Hyaluronic Acid Gels for Hydrocortisone Ocular Delivery.

This study endeavored to overcome the physiological barriers hindering optimal bioavailability in ophthalmic therapeutics by devising drug delivery platforms that allow therapeutically effective drug concentrations in ocular tissues for prolonged times. Thermosensitive drug delivery platforms were formulated by blending poloxamers (F68 and F127) with low-molecular-weight hyaluronic acid (HA) in various concentrations and loaded with hydrocortisone (HC). Among the formulations examined, only three were deemed suitable based on their desirable gelling properties at a temperature close to the eye's surface conditions while also ensuring minimal gelation time for swift ocular application. Rheological analyses unveiled the ability of the formulations to develop gels at suitable temperatures, elucidating the gel-like characteristics around the physiological temperature essential for sustained drug release. The differential scanning calorimetry findings elucidated intricate hydrogel-water interactions, indicating that HA affects the water-polymer interactions within the gel by increasing the platform hydrophilicity. Also, in vitro drug release studies demonstrated significant hydrocortisone release within 8 h, governed by an anomalous transport mechanism, prompting further investigation for optimized release kinetics. The produced platforms offer promising prospects for efficacious ocular drug delivery, addressing pivotal challenges in ocular therapeutics and heralding future advancements in the domain.

Ocular Distribution and Pharmacokinetics of 8-Oxo-2'-Deoxyguanosine: A Novel Therapeutic Candidate of Ocular Surface Diseases.

Purpose: This study evaluated the ocular distribution and plasma pharmacokinetics (PKs) of 8-oxo-2'-deoxyguanosine (8-oxo-dG) in rabbits and rats, respectively. Methods: A test formulation containing radiolabeled [14 C]8-oxo-dG and unlabeled 8-oxo-dG was ocularly administered to rabbits as a single dose of 1 mg per body and intravenously injected to rats as a single dose of 5 mg/kg. The ocular distribution of [14 C]8-oxo-dG was evaluated using autoradiography until 48 h postdose. Plasma radioactivity in rabbits and rats was determined until 72 and 168 h, respectively. Results: After ocular instillation, [14 C]8-oxo-dG distributed into ocular tissues, and high radioactivity concentrations were observed in the ciliary body, conjunctiva, and cornea. The maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC0-t) were highest in the ciliary body and conjunctiva, respectively. In the conjunctiva, cornea, and aqueous humor, time to reach Cmax (Tmax) was 0.5 h, and the half-lives were 11.2, 30.2, and 15.1 h, respectively. The radioactivity of [14 C]8-oxo-dG in plasma of rabbits displayed a double-peak phenomenon with the second peak considered as Cmax (37.9 ± 3.1 ng eq./mL) occurring 24 h postdose. After systemic exposure of [14 C]8-oxo-dG in rats, a rapid decline in the initial phase and a terminal half-life of 56.1 ± 31.3 h were observed. Conclusions: Rapid ocular distribution and high concentrations in anterior ocular tissues with minimal systemic exposure were observed after the ocular instillation of 8-oxo-dG in rabbits. These PK profiles are favorable for the treatment of ocular surface diseases.

A sensitive and rapid bioanalytical method for the quantitative determination of luliconazole in rabbit eye tissues using UPLC-MS/MS assay

Luliconazole (LCZ) is a novel antifungal imidazole with broad-spectrum and high susceptibility of Aspergillus and Fusarium are the dominant species of fungal keratitis, may potentially be a new medical treatment option for ocular fungal infection. To evaluate LCZ distribution in ocular tissues after topical application for the development of ophthalmic delivery system, it is important to have a bioanalytical method for measuring the drug concentrations in different ocular tissues and aqueous humor (AH). A selective and sensitive ultrahigh performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method was developed for the quantification of LCZ in rabbit ocular tissues, including conjunctiva, cornea, AH, iris, lens, vitreous humor (VH), retinal choroid and sclera, using lanoconazole as internal standard (IS). Chromatographic separation was achieved on a Xterra MS, C18 column (2.1 × 50 mm, 3.5 μm) using mobile phase with formic acid solution (0.2%, v/v): acetonitrile (50:50, v/v) at a flow rate of 0.2 ml/min, and the run time was 2.5 min. Detection was performed using the transitions 354.1 → 150.3 m/z for LCZ and 320.1 → 150.3 m/z for IS by positive ion electrospray ionization in multiple reaction monitoring (MRM) mode. Method validation was conducted in accordance with U.S. Food and Drug Administration’s regulatory guidelines for bioanalytical method validation. The calibration curves were linear over the concentration range from 2.80 ng/ml to 2038 ng/ml for conjunctiva, cornea and sclera, 2.09 ng/ml to 1019 ng/ml for AH, 2.09 ng/ml to 509.5 ng/ml for iris, 2.09 ng/ml to 203.8 ng/ml for retinal choroid and VH, 2.04 ng/ml to 101.9 ng/ml for lens, with all the squared correlation coefficients (r2) more than 0.99. The accuracy of the method was within the acceptable limit of 89.34%∼112.78% at the lower limit of quantification and other concentrations, Inter-day and intra-day precision values, expressed in terms of RSD (%), in all tissues were within 15% at all concentrations. The mean recoveries of LCZ in rabbit ocular tissues was 84.85%∼100.52%. No interference was found due to matrix components. Luliconazole was stable during the stability studies, including autosampler stability, benchtop stability, freeze/thaw stability and long-term stability. The method was successfully applied to the ocular pharmacokinetic and tissues distribution studies of LCZ in rabbit after topical administration of LCZ ophthalmic drug delivery system.

Quantification of Drugs in Distinctly Separated Ocular Substructures of Albino and Pigmented Rats.

The rat is a commonly used species in ocular drug research. Detailed methods of separating rat ocular tissues have not been described in literature. To understand the intraocular drug distribution, we developed a robust method for the separation of individual anterior and posterior substructures of pigmented Brown Norway (BN) and albino Wistar Han (WH) rat eyes, followed by quantification of drug concentration in these substructures. A short formalin incubation, which did not interfere with drug quantification, enabled the preservation of individual tissue sections while minimizing cross-tissue contamination, as demonstrated by histological analysis. Following oral administration, we applied the tissue separation method, in order to determine the ocular concentrations of dexamethasone and levofloxacin, as well as two in-house molecules BI 113823 and BI 1026706, compounds differing in their melanin binding. The inter-individual variability in tissue partitioning coefficients (Kp) was low, demonstrating the reproducibility of the separation method. Kp values of individual tissues varied up to 100-fold in WH and up to 46,000-fold in BN rats highlighting the importance of measuring concentration directly from the ocular tissue of interest. Additionally, clear differences were observed in the BN rat tissue partitioning compared to the WH rat. Overall, the developed method enables a reliable determination of small molecule drug concentrations in ocular tissues to support ocular drug research and development.

Ocular and systemic pharmacokinetics of brimonidine and brinzolamide after topical administration in rabbits: comparison between fixed-combination and single-drug formulations

ABSTRACT Aim The aim of this study was to compare the ocular and systemic absorption of brimonidine (BMD) and brinzolamide (BZM) in rabbits after the topical administration of a fixed-combination ophthalmic suspension of 0.1% BMD tartrate and 1% BZM (FCBB) with that after the administration of the respective single-drug formulations. Materials and Methods Ocular and systemic drug absorption was estimated by determining BMD and BZM concentrations in the aqueous humor, retina/choroid, vitreous body, and blood/plasma by liquid chromatography/tandem mass spectrometry after the administration of FCBB, 0.1% BMD tartrate ophthalmic solution (0.1% BMD), or 1% BZM ophthalmic suspension (1% BZM) to rabbits. Results In concomitant administration, instilling 0.1% BMD and 1% BZM successively without interval lowered aqueous humor concentrations of both drugs compared to those observed with a 5-min interval. After FCBB administration, BMD and BZM concentrations in the aqueous humor were comparable with those observed after the administration of 0.1% BMD and 1% BZM, whereas BMD concentrations in posterior ocular tissues were equal to or higher than those observed after 0.1% BMD. Plasma BMD concentrations following the administration of FCBB were 0.8-fold lower than those after 0.1% BMD; no remarkable differences were observed in blood BZM concentrations for both formulations. Conclusions FCBB achieved drug distribution in the aqueous humor and systemic exposure that were comparable to those for the single-drug formulations. The viscosity of FCBB may increase BMD distribution in the retina/choroid. The administration interval affects ocular drug absorption with the concomitant administration of 0.1% BMD and 1% BZM, which can be overcome by using the fixed-combination of both drugs.

Sustained-release voriconazole-thermogel for subconjunctival injection in horses: ocular toxicity and in-vivo studies

BackgroundKeratomycosis is a relatively common, sight threatening condition in horses, where treatment is often prolonged and costly. Subconjunctival (SCo) injections offer less resistance to drug diffusion than the topical route, resulting in better penetration to the ocular anterior segment. Voriconazole, a second generation triazole antifungal, is effective against common fungal organisms causing keratomycosis. If combined with a thermogel biomaterial, voriconazole can be easily injected in the SCo space to provide sustained drug release. The purpose of this study was to evaluate the drug concentrations in the anterior segment and clinical effects after SCo injections of voriconazole-containing thermogel: poly (DL-lactide-co-glycolide-b-ethylene glycol-b-DL-lactide-co-glycolide) (PLGA-PEG-PLGA) in healthy equine eyes.ResultsVoriconazole aqueous humor (AH) and tear concentrations were compared between 6 horses, receiving 1% voriconazole applied topically (0.2 mL, q4h) (Vori-Top) or 1.7% voriconazole-thermogel (0.3 mL) injected SCo (Vori-Gel). For the Vori-Gel group, voriconazole concentrations were measured in AH and tears at day 2 and then weekly for 23 days, and at day 2 only for the Vori-Top group. Ocular inflammation was assessed weekly (Vori-Gel) using the modified Hackett-McDonald scoring system. Ocular tissue concentrations of voriconazole following SCo 1.7% voriconazole-thermogel (0.3 mL) injections were evaluated post euthanasia in 6 additional horses at 3 different time points. Three horses received bilateral injections at 2 h (n = 3, right eye (OD)) and 48 h (n = 3, left eye (OS)) prior to euthanasia, and 3 horses were injected unilaterally (OS), 7 days prior to euthanasia. Voriconazole-thermogel was easily injected and well tolerated in all cases, with no major adverse effects. On day 2, drug concentrations in tears were higher in the Vori-Top, but not statistically different from Vori-Gel groups. For the Vori-Gel group, voriconazole was non-quantifiable in the AH at any time point. Total voriconazole concentrations in the cornea were above 0.5 μg/g (the target minimum inhibitory concentration (MIC) for Aspergillus sp.) for up to 48 h; however, concentrations were below this MIC at 7 days post treatment.ConclusionsVoriconazole-thermogel was easily and safely administered to horses, and provided 48 h of sustained release of voriconazole into the cornea. This drug delivery system warrants further clinical evaluation.

Incurred sample reanalysis of cefuroxime in rabbit ocular tissues-A case study.

In this paper, we present the incurred sample reanalysis (ISR) data for cefuroxime in various ocular tissues of rabbits. Based on the cefuroxime concentration vs. time profile in various ocular tissues, three chosen time points enabled ISR assessment. Cefuroxime was quantitated in the ocular tissues using a published liquid chromatography-electrospray ionization/tandem mass spectrometry method operated under the multiple reaction-monitoring mode in positive ion mode. Regardless of the ocular tissue, the linearity range was 12.7-2760 ng/ml with a correlation coefficient (r2 ) of ≥0.996. All of the ISR samples representing various ocular tissues met the acceptance criteria. To the best of our knowledge, this is the first report showing the ISR of ocular tissues in any species.

Antibiotic Resistance Among Pediatric-Sourced Ocular Pathogens: 8-Year Findings From the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) Surveillance Study.

The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) study is a nationwide longitudinal antibiotic resistance surveillance program specific to bacterial pathogens commonly encountered in ocular infections. We evaluated in vitro resistance rates and trends among isolates obtained from pediatric patients (≤17 years of age). Clinical centers across the United States were invited to submit ocular isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Haemophilus influenzae and Pseudomonas aeruginosa to a central laboratory. Minimum inhibitory concentrations for various antibiotic classes were determined by broth microdilution per Clinical and Laboratory Standards Institute guidelines and interpreted as susceptible, intermediate or resistant based on available breakpoints. Longitudinal trends were analyzed using a Cochran-Armitage test for linear trends in a proportion. Of 4829 isolates collected from January 2009 to December 2016, 995 isolates, sourced primarily from hospitals and referral centers, were obtained from pediatric patients (n = 286 H. influenzae, n = 284 S. aureus, n = 213 CoNS, n = 150 S. pneumoniae and n = 62 P. aeruginosa). With few exceptions, P. aeruginosa and H. influenzae were generally susceptible to the antibiotics tested. Of S. aureus and CoNS isolates, respectively, 56% and 72% were resistant to azithromycin and 24% and 47% were methicillin-resistant (MR); concurrent resistance to other drug classes and multidrug resistance (≥3 drug classes) were prevalent among MR staphylococci. Of S. pneumoniae isolates, 38% and 35% demonstrated resistance to azithromycin and penicillin, respectively. Besifloxacin had the lowest minimum inhibitory concentration against the Gram-positive isolates. These in vitro data suggest antibiotic resistance is common among staphylococcal and pneumococcal isolates collected from pediatric patients with ocular infections. Methicillin resistance was prevalent among staphylococci with many strains demonstrating multidrug resistance. These findings may not be representative of resistance trends in community-based practices.

Comparative Study of Ocular Pharmacokinetics of Gatifloxacin Between Continuous Lavage and Hourly Topical Instillation in Rabbits

To investigate the ocular pharmacokinetics and distribution of gatifloxacin between continuous lavage through the Morgan lens and repeated topical drop instillation in rabbits. Thirty-six healthy rabbits were randomly divided into 2 groups, and 0.3% gatifloxacin ophthalmic solution was instilled by continuous lavage using the Morgan lens onto the left eyes at 15 mL/h (or 50 μL of the same solution repeatedly administered topically every hour). The animals were killed at 2, 4, 8, and 12 hours in the Morgan lens group or at 12 and 24 hours in the topical instillation group. Aqueous humor specimens were collected from the anterior chamber first, and other ocular tissues and plasma were collected subsequently. Pharmacokinetic and pharmacodynamic indices, other than the minimum inhibitory concentration (MIC), were used as therapeutic parameters in ocular tissues. The highest concentration was found in the corneas in both groups. With continuous lavage, gatifloxacin reached an efficacious high concentration in 4 hours in the cornea, which is equivalent to about 23 times the concentration reached in the same tissue by hourly topical instillation for 12 to 24 hours. Using historic data as references, C/MIC90 was 105 (>10) and AUC0-t/MIC90 was 194 h (>125) in the cornea in the continuous lavage group at 4 hours, whereas these values were 5 and 73 hours for the topical hourly instillation group. Compared with hourly topical instillation, continuous lavage through the Morgan lens could achieve significantly higher concentrations in ocular tissues within a short period, especially in the cornea. Continuous lavage may be a much more efficient way to treat recalcitrant corneal infections.

Preclinical pharmacokinetics of a recombinant humanized rabbit anti-VEGF monoclonal antibody in rabbits and monkeys

TMAB001 is a humanized rabbit monoclonal antibody (mAb) designed to bind and neutralize human vascular endothelial growth factor (VEGF)-165. The purpose of the study was to investigate the pharmacokinetics (PK) and ocular tissue distribution after a single intravitreal (IVT) dose in rabbits and monkeys.Rabbits (2.5 mg/eye; n = 40) and monkeys (2.5 mg/eye; n = 12) received TMAB001 as a bilateral IVT dose. TMAB001 concentrations were measured in ocular tissues in all rabbits and monkeys by enzyme-linked immunosorbent assay (ELISA). TMAB001 and VEGF concentrations were measured in serum of monkeys by ELISA.Following a single bilateral IVT injection of TMAB001 2.5 mg/eye, the highest concentration was in vitreous humor, followed by retina and choroid, and the lowest concentration was in lens. In rabbits, TMAB001 was still detectable in ocular tissues at day 21 after single IVT dose, with the highest level in the vitreous humor and then retina, with longest t1/2 in aqueous humor and shortest t1/2 in choroid. In monkeys, tmax in serum was 43 h and t1/2 was approximately 5.5 days. Cmax in serum was much lower than that in vitreous, nearly 1/200. After IVT injection of TMAB001, total VEGF concentrations in serum and ocular tissues increased over time. VEGF concentration in retina and choroid increased over time, up to 336 h after administration.This study demonstrated that TMAB001 could reach the drug target sites–retina and choroid after a single bilateral IVT administration in rabbits and monkeys, with a long t1/2 in vitreous humor. TMAB001 also showed strong capability to neutralize VEGF. The study further confirmed that full-length antibodies can also efficiently diffuse and distribute in ocular tissues.

Immunosuppression by a subconjunctival implant releasing dexamethasone in a rabbit model of penetrating keratoplasty

AimsTo evaluate the efficacy of a subconjunctival dexamethasone-releasing implant in preventing rejection of penetrating keratoplasty (PK) in an animal model.MethodsTwenty-two rabbits underwent allogenic PK. After randomisation, they received either a...

In Silico Ocular Pharmacokinetic Modeling: Delivery of Topical FK962 to Retina.

To establish the in silico ocular pharmacokinetic modeling for eye drops, and to simulate the dose regimen for FK962 in human choroid/retinal diseases. Pharmacokinetics for FK962 in vivo was performed by a single instillation of drops containing 0.1% 14C-FK962 in rabbit eyes. Permeation of FK962 across the cornea, sclera, and choroid/retina was measured in vitro. Neurite elongation by FK962 was measured in cultured rat retinal ganglion cells. Parameters from the experimental data were used in an improved in silico model of ocular pharmacokinetics of FK962 in man. The mean concentration of FK962 in ocular tissues predicted by in silico modeling was consistent with in vivo results, validating the in silico model. FK962 rapidly penetrated into the anterior and posterior segments of the eye and then diffused into the vitreous body. The in silico pharmacokinetic modeling also predicted that a dose regimen of 0.0054% FK962 twice per day would produce biologically effective concentrations of FK962 in the choroid/retina, where FK962 facilitates rat neurite elongation. Our in silico model for ocular pharmacokinetics is useful (1) for predicting drug concentrations in specific ocular tissues after topical instillation, and (2) for suggesting the optimal dose regimens for eye drops. The pharmacodynamics for FK962 produced by this model may be useful for clinical trials against retinal neuropathy.

Mucoadhesive niosomal in situ gel for ocular tissue targeting: in vitro and in vivo evaluation of lomefloxacin hydrochloride

Eradication of ophthalmic infections depends on increasing transcorneal permeation and localizing antibiotics at ocular surface. This study aimed at formulating lomefloxacin HCl (LF) in the form of niosomes and evaluating the in vivo performance of best formula in rabbits’ eyes. Vesicles were developed by mixing three surfactants at three molar ratios of 1:1, 1:2 and 1:3 of surfactant to cholesterol. Size, zeta potential, release percentage, transcorneal permeation parameters, stability studies, cytotoxicity and antibacterial activity of niosomes were determined. Niosomes showed encapsulation efficiency of more than 78%, particle size below 500 nm and zeta potential below −43.6. The produced vesicles showed significantly higher amounts of drug permeated across cornea (166%) compared to LF solution. The in vivo study showed 2–5 folds increase in drug concentration in ocular fluids and tissues following administration of niosomes compared to marketed formula (from 3.75 to 10.31 mcg/mL in the cornea). Microbiological studies showed 35 folds increase in the antibacterial activity of LF niosomes compared to free drug; where MBC decreased from 31.25 mcg/mL in case of LF solution to 0.97 mcg/mL for niosomal gel. The formulated niosomes enhanced the ocular bioavailability of LF through increasing transcorneal permeation and localizing drug at site of action.

Topical delivery of aqueous micellar resolvin E1 analog (RX-10045)

PurposeThe primary objective of this study were to optimize aqueous micellar solution of isopropyl ester prodrug of resolvin (RX-10045), study in vivo ocular compatibility and tissue distribution following topical administration. MethodsAn optimized ratio of hydrogenated castor-oil and octoxynol-40 (1.0:0.05wt%) was prepared to entrap RX-10045 in the hydrophobic core of micelles. RX-10045 aqueous micelles were subjected to characterization. In vitro stability studies were performed at 4°C, 25°C and 40°C. In vivo studies were conducted in New Zealand albino rabbits following topical drop administration. ResultsAqueous RX-10045 micellar solutions were successfully prepared. Micelles had a mean diameter of ∼12nm with low negative surface charge. RX-10045 demonstrated high stability in citrate buffer (0.01M) at 40°C. Hackett–McDonald ocular irritation scores were extremely low comparable to negative control. No significant difference in intraocular pressure was noted. Electroretinography studies did not reveal any retinal damage after multiple dosing of RX-10045 micellar solution. Ocular tissue distribution studies demonstrated appreciable drug concentrations in anterior ocular tissues. Moreover, RX-10008 (active metabolite of RX-10045) was detected in retina/choroid upon topical drop instillation. ConclusionsA clear, stable, aqueous 0.1% RX-10045 micellar formulation was successfully prepared. Micellar solution was well-tolerated and did not have any measurable tissue damage in rabbit ocular tissues. Micelles appear to follow conjunctival/scleral pathway to reach back-of-the-eye tissue (retina). Topical aqueous formulations may be employed to treat posterior ocular diseases. Such micellar topical formulations may be more patient acceptable over invasive routes of administrations such as intravitreal injection/implants.

In Vitro/In Vivo Evaluation of Dexamethasone—PAMAM Dendrimer Complexes for Retinal Drug Delivery

Current treatment options for diabetic retinopathy (DR) have side effects because of invasive application and topical application does not generally result in therapeutic levels in the target tissue. Therefore, improving the drug delivery to retina, following topical administration, might be a solution to DR treatment problems. The purpose of this study was to investigate the complexation effects of poly(amidoamine) (PAMAM) dendrimers on ocular absorption of dexamethasone (DEX). Using different PAMAM generations, complex formulations were prepared and characterized. Formulations were evaluated in terms of cytotoxicity and cell permeability, as well as ex vivo transport across ocular tissues. The ocular pharmacokinetic properties of DEX formulations were studied in Sprague-Dawley rats following topical and subconjunctival applications, to evaluate the effect of PAMAM on retinal delivery of DEX. Methyl-thiazol-tetrazolium (MTT) assay indicated that all groups resulted in cell viability comparable to DEX solution (87.5%), with the cell viability being the lowest for G3 complex at 73.5%. Transport study results showed that dendrimer complexation increases DEX transport across both cornea and sclera tissues. The results of in vivo studies were also indicated that especially anionic DEX-PAMAM complex formulations have reached higher DEX concentrations in ocular tissues compared with plain DEX suspension.

Topical, Aqueous, Clear Cyclosporine Formulation Design for Anterior and Posterior Ocular Delivery.

The main objective of this study was to optimize cyclosporine (CsA) nanomicellar solution and study in vivo ocular CsA tissue distribution with a topical drop. An optimized blend of hydrogenated castor oil-40 and octoxynol-40 was prepared to entrap CsA within nanomicelles. In vivo studies were conducted in New Zealand White albino rabbits with topical drop instillation. Average size of CsA-loaded nanomicelles was approximately 22.4 nm. Ocular tissue CsA quantification with single and multiple dosing revealed that CsA levels followed as cornea → iris-ciliary body → aqueous humor → lens. Cyclosporine levels were also found to be in the following order: conjunctiva → sclera → retina/choroid → vitreous humor. High CsA level was detected in retina/choroid (53.7 ng/g tissue). Ocular tissue CsA distribution studies revealed high CsA concentrations in anterior ocular tissues. Moreover, it appears that nanomicelles are transported through a conjunctival-scleral pathway and deliver CsA to the retina/choroid. Results suggest polymeric blend to be a safe carrier for anterior and posterior ocular tissues. This study has significant translational relevance, disclosing results that suggest that aqueous nanomicellar approach can provide high corneal and conjunctival CsA concentrations. Aqueous nanomicelles can deliver high drug concentrations not only to anterior but also to back of the eye tissues, including retina. This article provides a platform for noninvasive back of the eye drug delivery with topical eye drops. Aqueous CsA nanomicelles have no perceptible toxicity such as cell membrane damage or cytotoxicity to corneal and retinal pigment epithelial cells. Clear aqueous nanomicellar solution can be translated to human conditions for keratoconjunctivitis sicca and other anti-inflammatory conditions.

Evaluation of topical hesperetin matrix film for back-of-the-eye delivery

PurposeThe goal of the present study was to develop a poly (ethylene oxide) N10 (PEO N10) based melt-cast matrix system for efficient and prolonged delivery of hesperetin (HT), a promising bioflavonoid, to the posterior segment of the eye through the topical route. MethodsHT film was prepared by melt-cast method using PEO N10 and cut into 4mm×2mm segments, each weighing 8mg. This film was evaluated with respect to in vitro release rates and also transmembrane delivery across Spectra/Por® membrane (MWCO: 10,000 Daltons) and isolated rabbit corneas. Ocular tissue concentrations were also determined postapplication of the film in ex vivo and in vivo models. ResultsHT release from the film was determined to be about 95.3% within 2h. In vitro transcorneal flux was observed to be 0.58±0.05μg/min/cm2 across the isolated rabbit cornea. High levels of HT were detected in the retina-choroid (RC) and vitreous humor (VH) in the ex vivo model following topical application of the film. Significant levels of HT were observed in both anterior and posterior segment ocular tissues 1h post topical application of the 10 and 20%w/w HT films on the rabbit eye. Moreover, HT was detected in the VH and RC even after 6h following topical application of the film in vivo. ConclusionThe results from this study suggest that the melt-cast films can serve as a viable platform for sustained topical delivery of bioflavonoids, and other therapeutic agents, into the back-of-the eye tissues.

Preclinical evaluation of a ricinoleic acid poloxamer gel system for transdermal eyelid delivery.

Our previous study has shown that pluronic lecithin organogel (PLO gel) made of ricinoleic acid has the potential for use as a transdermal eyelid delivery system. The present study deals with the evaluation of ocular tissue concentrations of dexamethasone in a rabbit model following topical application of the gel formulation onto the eyelids. The PLO gel formulation containing dexamethasone was applied to the outside of the eyelid skin. Rabbits were sacrificed at regular time intervals of 2, 4, 8, 12, 20 and 24h. Maxidex(®) eye drops were used as a control. Rabbits were sacrificed and dexamethasone concentrations were analyzed in anterior segment tissues such as the cornea, conjunctiva, aqueous humor, lens, and iris-ciliary body by liquid chromatography tandem mass spectrometry (LC-MS/MS). Rabbit eyes were also examined for ocular irritation and scored using the modified Draize scoring system. No significant irritation or redness was observed in the eyes as compared to the control rabbit eyes. PLO gel formulation resulted in constant dexamethasone concentrations in the anterior segment tissues for up to 24h, which was equivalent or higher than Maxidex(®) eye drops. The findings of this investigation indicate that the ricinoleic acid PLO gel formulation may be clinically effective as a new treatment modality for anterior segment diseases.

Understanding corneal permeation of lincosamide antimicrobials: in-vitro studies with synthetic stromal models

Purpose: Lincomycin and clindamycin are structurally related antimicrobials useful for treatment of both Gram- positive and Gram-negative anaerobes. On topical application therapeutic levels are attained in the cornea, aqueous humor, and iris-ciliary body, but despite structural similarity, behavioural differences occur. Clindamycin has higher overall concentration and shorter peak onset values in ocular tissues. This poster describes the use of in-vitro permeation through a corneal stromal model in the study of these behavioural differences.