Drug Delivery Options for the Treatment of Ocular Inflammation

Understanding dexamethasone kinetics in the rabbit tear fluid: drug release and clearance from solution, suspension and hydrogel formulations

Rapid precorneal loss of topically applied eye drops limits ocular drug absorption. Controlling release and precorneal residence properties of topical formulations may improve ocular drug bioavailability and duration of action. In this study, we evaluated in vivo ocular pharmacokinetics of dexamethasone in rabbits after application of a drug solution (0.01%), suspension (Maxidex® 0.1%), and hydrogels of 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AAc) copolymers. The rabbits received a single eyedrop (solution or suspension) or dexamethasone-loaded hydrogel topically. Dexamethasone in tear fluid was sampled with glass capillaries and quantitated by LC-MS/MS. Higher dexamethasone exposure (AUC) in the tear fluid was observed with the suspension (≈ 3.6-fold) and hydrogel (12.8-fold) as compared to the solution. During initial 15 min post-application, the highest AUC of dissolved dexamethasone was seen after hydrogel application (368 min*µg/mL) followed by suspension (109.9 min*µg/mL) and solution (28.7 min*µg/mL. Based on kinetic simulations, dexamethasone release from hydrogels in vivo and in vitro is comparable. Our data indicate that prolonged exposure of absorbable dexamethasone in tear fluid is reached with hydrogels and suspensions. Pharmacokinetic understanding of formulation behavior in the lacrimal fluid helps in the design of dexamethasone delivery systems with improved ocular absorption and prolonged duration of action.

Recent Advances in the Design of Topical Ophthalmic Delivery Systems in the Treatment of Ocular Surface Inflammation and Their Biopharmaceutical Evaluation

Ocular inflammation is one of the most common symptom of eye disorders and diseases. The therapeutic management of this inflammation must be rapid and effective in order to avoid deleterious effects for the eye and the vision. Steroidal (SAID) and non-steroidal (NSAID) anti-inflammatory drugs and immunosuppressive agents have been shown to be effective in treating inflammation of the ocular surface of the eye by topical administration. However, it is well established that the anatomical and physiological ocular barriers are limiting factors for drug penetration. In addition, such drugs are generally characterized by a very low aqueous solubility, resulting in low bioavailability as only 1% to 5% of the applied drug permeates the cornea. The present review gives an updated insight on the conventional formulations used in the treatment of ocular inflammation, i.e., ointments, eye drops, solutions, suspensions, gels, and emulsions, based on the commercial products available on the US, European, and French markets. Additionally, sophisticated formulations and innovative ocular drug delivery systems will be discussed. Promising results are presented with micro- and nanoparticulated systems, or combined strategies with polymers and colloidal systems, which offer a synergy in bioavailability and sustained release. Finally, different tools allowing the physical characterization of all these delivery systems, as well as in vitro, ex vivo, and in vivo evaluations, will be considered with regards to the safety, the tolerance, and the efficiency of the drug products.

Pharmacokinetics after Periocular Methylprednisolone Sodium Succinate Injection in Rabbit Eyes

The present study aimed to determine the pharmacokinetics and distribution of methylprednisolone sodium succinate (MPSS) and its metabolic product methylprednisolone (MP) in plasma and ocular tissues after periocular injection of MPSS in rabbit eyes. Forty-eight healthy New Zealand white rabbits were randomly divided into 12 groups, including the control group and 11 MPSS-treated groups sampling at different time points. Rabbits in the MPSS-treated groups underwent left eye periocular injection of MPSS (10 mg). The pharmacokinetics of MPSS and MP in plasma and ocular tissues (including aqueous humor, vitreous, iris, lens, sclera, optic nerve, and choroid and retina) were investigated by liquid chromatography tandem mass spectrometry (LC-MS/MS). After periocular injection, the time of maximum concentration (T_max) of MPSS ranged from 0.25 h to 1 h in ocular tissues and was 0.25 h in plasma. T_max of MP in ocular tissues ranged from 0.5 h to 6 h, and T_max of MP in plasma was 0.5 h. The maximum concentration (C_max) of MPSS and MP and the area under the curve (AUC_0-t) in ocular tissues from high to low was sclera, optic nerve, choroid and retina, iris, and lens. Especially, the concentrations of MPSS and MP in the lens were much lower when compared with the other ocular tissues. After periocular administration, MPSS could be rapidly metabolized to its active constituent MP in the ocular tissues. Also, the MPSS can be delivered effectively into the posterior segment of the eye (choroid and retina), while not easily be absorbed by the lens.

Periocular triamcinolone acetonide injection for treating polypoidal choroidal vasculopathy concurrent with hemorrhagic retinal detachment

To investigate the clinical efficiency of periocular triamcinolone acetonide (TA) injection for treating polypoidal choroidal vasculopathy (PCV) concurrent with hemorrhagic retinal detachment (HRD).Twenty-two cases confirmed with PCV concurrent with HRD characterized by massive subretinal hemorrhage and exudation presented to our department from January 2015 to May 2017 were included in this study. The initial vision varied from counting finger to 0.2. All cases were randomly divided into TA group (n = 12), which received periocular TA injection per month, and anti-VEGF group (n = 10), which were treated by anti-VEGF intravitreous injection per month. The patients were followed up for 6 months, in which fundus examination and visual acuity along with optical coherence tomography (OCT) were carried out.The treatment effect is divided into the following categories. Cure was defined as the elimination of subretinal hemorrhage and exudation accompanied by retinal edema and choroidal neovascularization (CNV) extinction and rise of visual acuity. Improvement was characterized by alleviation of subretinal hemorrhage and exudation accompanied by retinal edema and CNV reduction and rise of visual acuity. Ineffective means remained subretinal hemorrhage and exudation in fundus and no improvement of visual acuity, and polypoid lesions in OCT images. Among the 12 cases in TA group, 1 case was treated by periocular injection of TA twice, and 11 cases were treated by 3 times injection. After that, 3 cases (25%) were cured, 8 cases (66.7%) got improvement, and only 1 case (8.3%) showed no response. Although among 10 cases in the anti-VEGF group, 3 cases were treated by anti-VEGF intravitreous injection twice. Seven cases were treated by 3 times injection. After that, 4 cases (40%) got improvement, and the other 6 case (60%) showed no response. All patients showed no recurrence in the 6-month follow-up. No complications were noticed under periocular injection or intravitreous injection.Periocular TA injection is effective for treating PCV concurrent with HRD.

A comprehensive review on contact lens for ophthalmic drug delivery

With the prevalence of electronic devices and an aging population, the number of people affected with eye disease is increasing year by year. In spite of a large number of eye drops on the market, most of them do not perform sufficiently, due to rapid clearance mechanisms and ocular barriers. To enhance drug delivery to the eye, a number of novel formulations for ocular diseases have been investigated over recent decades, aiming to increase drug retention and permeation while also allowing for sustained drug release over prolonged periods. The contact lens, initially used to correct visual acuity and beautify female eyes, is one such novel formulation with outstanding potential. Recently, contact lenses have been extensively used for ocular drug delivery to enhance ocular bioavailability and reduce side effects, and are particularly suitable for the treatment of chronic diseases, and thus are of interest to ophthalmic scientists. This review summarizes contact lens classification, methods of preparation, strategies for integrating drugs into lenses, in vitro and in vivo studies, and clinical applications. This review also discusses the current state of ocular drug therapy and provides an outlook for future therapeutic opportunities in the field of ocular drug delivery.

Ocular Complications of Diabetes and Therapeutic Approaches

Diabetes mellitus (DM) is a metabolic disease defined by elevated blood glucose (BG). DM is a global epidemic and the prevalence is anticipated to continue to increase. The ocular complications of DM negatively impact the quality of life and carry an extremely high economic burden. While systemic control of BG can slow the ocular complications they cannot stop them, especially if clinical symptoms are already present. With the advances in biodegradable polymers, implantable ocular devices can slowly release medication to stop, and in some cases reverse, diabetic complications in the eye. In this review we discuss the ocular complications associated with DM, the treatments available with a focus on localized treatments, and what promising treatments are on the horizon.

Intraocular Implants for the Treatment of Autoimmune Uveitis

Uveitis is the third leading cause of blindness in developed countries. Currently, the most widely used treatment of non-infectious uveitis is corticosteroids. Posterior uveitis and macular edema can be treated with intraocular injection of corticosteroids, however, this is problematic in chronic cases because of the need for repeat injections. Another option is systemic immunosuppressive therapies that have their own undesirable side effects. These systemic therapies result in a widespread suppression of the entire immune system, leaving the patient susceptible to infection. Therefore, an effective localized treatment option is preferred. With the recent advances in bioengineering, biodegradable polymers that allow for a slow sustained-release of a medication. These advances have culminated in drug delivery implants that are food and drug administration (FDA) approved for the treatment of non-infectious uveitis. In this review, we discuss the types of ocular implants available and some of the polymers used, implants used for the treatment of non-infectious uveitis, and bioengineered alternatives that are on the horizon.

Side-effects of anti-inflammatory therapy in uveitis

Uveitis is a group of inflammatory ocular conditions that cause significant visual morbidity around the world. Many of the cases of blindness secondary to uveitis can be avoided with adequate and aggressive management of the intraocular inflammation. Steroids have been utilized in the treatment of noninfectious uveitis for more than 60 years, but their chronic use is associated with severe ocular and systemic side-effects. Ophthalmologists are often not familiar with the systemic steroid-sparing agents available for the management of ocular inflammation and depend primarily on the use of corticosteroids. In this article, we review the most common agents utilized in the treatment of uveitis and their side-effect profiles.

Successful factorial design for the optimization of methylprednisolone encapsulation in biodegradable nanoparticles

Due to their crystalline nature, the encapsulation of hydrophobic corticosteroids within polymeric nanoparticles by o/w solvent evaporation method is often difficult to achieve. The aim of this study was to evaluate the effect of both process and formulation parameters on the encapsulation of a model corticosteroid: methylprednisolone (MP). For this purpose, a 3(2)factorial design was performed evaluating the effects of the concentration of emulsifiers and sonication time on the manufactured nanoparticles, followed by a multiresponse optimization. The study also included the evaluation of other parameters such as the type of organic solvent used, polymer characteristics and the initial mass of drug. The optimal nanoparticle formulation using 0.25% (w/v) of emulsifying agent (Polyvinyl-alcohol, PVA) and 5 min of sonication was then characterized. The highest encapsulation was obtained with an organic phase consisting of acetone: dichloromethane (1:1), polyD,L-lactide-co-glycolide (PLGA) 50:50 as polymer and an initial mass of 6.6 mg of methylprednisolone. Nanoparticles size and ζ potential of optimized formulation were respectively around 230 nm and -14 mV. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) demonstrated that the drug was molecularly dispersed within the nanoparticles. Release study showed that MP-loaded nanoparticles sustained drug release for up to 120 h. This study reflects the importance of factorial design to optimize the manufacture of nanoparticles encapsulating hydrophobic drugs.

Dexamethasone intravitreal implant for the treatment of noninfectious uveitis

Uveitis can be a sight-threatening eye disease with significant morbidity. Corticosteroids remain the mainstay of treatment of uveitis and provide an effective treatment against ocular inflammation. However, the various modes available for corticosteroid drug delivery can carry significant ocular and systemic side effects which can limit their use in the treatment of uveitis. In an effort to avoid the damage to ocular structures that can ensue with recurrent episodes of ocular inflammation, the side effects associated with systemic steroids, and the need for repeated administration of both topical and locally injected corticosteroids, sustained-release intraocular corticosteroid implants have been developed. The dexamethasone (DEX) drug delivery system (Ozurdex(®); Allergan Inc, Irvine, CA), is a biodegradable intravitreal implant. This implant has been shown to be effective in the treatment of macular edema and noninfectious posterior uveitis and has been approved by the FDA for these entities. This review will highlight the current methods available for corticosteroid delivery to the eye with a particular emphasis on the DEX intravitreal implant and the evidence currently available for its use in noninfectious uveitis.