Two multicenter, randomized studies of the efficacy and safety of cyclosporine ophthalmic emulsion in moderate to severe dry eye disease. CsA Phase 3 Study Group

OBJECTIVE

To compare the efficacy and safety of cyclosporin A ([CsA] 0.05% and 0.1% ophthalmic emulsions) to vehicle in patients with moderate to severe dry eye disease.

DESIGN

Multicenter, randomized, double-masked, parallel-group, 6-month, vehicle-controlled.

PARTICIPANTS

A total of 877 patients with defined moderate to severe dry eye disease (292 to 293 in each treatment group).

METHODS

Two identical clinical trials; patients were treated twice daily with either CsA, 0.05% or 0.1%, or vehicle. The results of these two trials were combined for analysis.

MAIN OUTCOME MEASURES

EFFICACY

corneal and interpalpebral dye staining, Schirmer tear test (with and without anesthesia), tear break-up time, Ocular Surface Disease Index (OSDI), facial expression, patient subjective rating scale, symptoms of dry eye, investigator's evaluation of global response to treatment, treatment success, and daily use of artificial tears.

SAFETY

occurrence of adverse events, best-corrected visual acuity, intraocular pressure, biomicroscopy, and blood trough CsA concentrations.

RESULTS

Treatment with CsA, 0.05% or 0.1%, gave significantly (P < or = 0.05) greater improvements than vehicle in two objective signs of dry eye disease (corneal staining and categorized Schirmer values). CsA 0.05% treatment also gave significantly greater improvements (P < 0.05) in three subjective measures of dry eye disease (blurred vision, need for concomitant artificial tears, and the physician's evaluation of global response to treatment). There was no dose-response effect. Both CsA treatments exhibited an excellent safety profile, and there were no significant topical or systemic adverse safety findings.

CONCLUSIONS

The novel ophthalmic formulations CsA 0.05% and 0.1% were safe and effective in the treatment of moderate to severe dry eye disease yielding improvements in both objective and subjective measures. Topical CsA represents a new pharmacologically based treatment for dry eye disease that may provide significant patient benefits.

Latanoprost for open-angle glaucoma (UKGTS): a randomised, multicentre, placebo-controlled trial

BACKGROUND

Treatments for open-angle glaucoma aim to prevent vision loss through lowering of intraocular pressure, but to our knowledge no placebo-controlled trials have assessed visual function preservation, and the observation periods of previous (unmasked) trials have typically been at least 5 years. We assessed vision preservation in patients given latanoprost compared with those given placebo.

METHODS

In this randomised, triple-masked, placebo-controlled trial, we enrolled patients with newly diagnosed open-angle glaucoma at ten UK centres (tertiary referral centres, teaching hospitals, and district general hospitals). Eligible patients were randomly allocated (1:1) with a website-generated randomisation schedule, stratified by centre and with a permuted block design, to receive either latanoprost 0·005% (intervention group) or placebo (control group) eye drops. Drops were administered from identical bottles, once a day, to both eyes. The primary outcome was time to visual field deterioration within 24 months. Analyses were done in all individuals with follow-up data. The Data and Safety Monitoring Committee (DSMC) recommended stopping the trial on Jan 6, 2011 (last patient visit July, 2011), after an interim analysis, and suggested a change in primary outcome from the difference in proportions of patients with incident progression between groups to time to visual field deterioration within 24 months. This trial is registered, number ISRCTN96423140.

FINDINGS

We enrolled 516 individuals between Dec 1, 2006, and March 16, 2010. Baseline mean intraocular pressure was 19·6 mm Hg (SD 4·6) in 258 patients in the latanoprost group and 20·1 mm Hg (4·8) in 258 controls. At 24 months, mean reduction in intraocular pressure was 3·8 mm Hg (4·0) in 231 patients assessed in the latanoprost group and 0·9 mm Hg (3·8) in 230 patients assessed in the placebo group. Visual field preservation was significantly longer in the latanoprost group than in the placebo group: adjusted hazard ratio (HR) 0·44 (95% CI 0·28-0·69; p=0·0003). We noted 18 serious adverse events, none attributable to the study drug.

INTERPRETATION

This is the first randomised placebo-controlled trial to show preservation of the visual field with an intraocular-pressure-lowering drug in patients with open-angle glaucoma. The study design enabled significant differences in vision to be assessed in a relatively short observation period.

FUNDING

Pfizer, UK National Institute for Health Research Biomedical Research Centre.

Ophthalmic drug delivery systems--recent advances

Eye-drops are the conventional dosage forms that account for 90% of currently accessible ophthalmic formulations. Despite the excellent acceptance by patients, one of the major problems encountered is rapid precorneal drug loss. To improve ocular drug bioavailability, there is a significant effort directed towards new drug delivery systems for ophthalmic administration. This chapter will focus on three representative areas of ophthalmic drug delivery systems: polymeric gels, colloidal systems, cyclodextrins and collagen shields. Hydrogels generally offer a moderate improvement of ocular drug bioavailability with the disadvantage of blurring of vision. In situ activated gel-forming systems are preferred as they can be delivered in drop form with sustained release properties. Colloidal systems including liposomes and nanoparticles have the convenience of a drop, which is able to maintain drug activity at its site of action and is suitable for poorly water-soluble drugs. Among the new therapeutic approaches in ophthalmology, cyclodextrins represent an alternative approach to increase the solubility of the drug in solution and to increase corneal permeability. Finally, collagen shields have been developed as a new continuous-delivery system for drugs that provide high and sustained levels of drugs to the cornea, despite a problem of tolerance. It seems that new tendency of research in ophthalmic drug delivery systems is directed towards a combination of several drug delivery technologies. There is a tendency to develop systems which not only prolong the contact time of the vehicle at the ocular surface, but which at the same time slow down the elimination of the drug. Combination of drug delivery systems could open a new directive for improving results and the therapeutic response of non-efficacious systems.

Surgical reconstruction of the ocular surface in advanced ocular cicatricial pemphigoid and Stevens-Johnson syndrome

PURPOSE

Ocular cicatricial pemphigoid and Stevens-Johnson syndrome often cause ocular damage and blindness not amenable to surgical correction. We present a new surgical technique for reconstructing affected eyes.

METHODS

Fourteen eyes of 11 patients with cicatricial keratoconjunctivitis (seven patients with cicatricial pemphigoid and four with Stevens-Johnson syndrome; average age +/- S.D., 55.5 +/- 25.4 years) were treated with a combination of allograft limbal transplantation, amniotic membrane transplantation, and tarsorrhaphy, followed every 15 minutes by artificial tears derived from the patient's blood serum. Eight eyes required concomitant penetrating or lamellar keratoplasty because of corneal opacity.

RESULTS

With a mean follow-up of 143 days (range, 10 to 608 days), we achieved successful ocular surface reconstruction in 12 eyes, with minimal recurrence of symblepharon. Failure occurred in two eyes (one each in 9- and 10-year-old boys) that developed corneal infiltration and vascularization.

CONCLUSIONS

A combination of allograft limbal transplantation, amniotic membrane transplantation, and tarsorrhaphy, followed by the use of serum-derived tears, can reconstruct the ocular surface in most cases. Although in this study the follow-up period was short and relatively few patients were studied, this approach appears to offer an alternative to keratoprosthesis for treating severe cicatricial keratoconjunctivitis with dry eye.

Polymeric micelles for ocular drug delivery: From structural frameworks to recent preclinical studies

Effective intraocular drug delivery poses a major challenge due to the presence of various elimination mechanisms and physiological barriers that result in low ocular bioavailability after topical application. Over the past decades, polymeric micelles have emerged as one of the most promising drug delivery platforms for the management of ocular diseases affecting the anterior (dry eye syndrome) and posterior (age-related macular degeneration, diabetic retinopathy and glaucoma) segments of the eye. Promising preclinical efficacy results from both in-vitro and in-vivo animal studies have led to their steady progression through clinical trials. The mucoadhesive nature of these polymeric micelles results in enhanced contact with the ocular surface while their small size allows better tissue penetration. Most importantly, being highly water soluble, these polymeric micelles generate clear aqueous solutions which allows easy application in the form of eye drops without any vision interference. Enhanced stability, larger cargo capacity, non-toxicity, ease of surface modification and controlled drug release are additional advantages with polymeric micelles. Finally, simple and cost effective fabrication techniques render their industrial acceptance relatively high. This review summarizes structural frameworks, methods of preparation, physicochemical properties, patented inventions and recent advances of these micelles as effective carriers for ocular drug delivery highlighting their performance in preclinical studies.

Efficacy and safety of cyclosporin A ophthalmic emulsion in the treatment of moderate-to-severe dry eye disease: a dose-ranging, randomized trial. The Cyclosporin A Phase 2 Study Group

OBJECTIVE

To investigate the efficacy, safety, formulation tolerability, and optimal dosing of a novel cyclosporin A oil-in-water emulsion formulation for the treatment of moderate-to-severe dry eye disease.

DESIGN

Randomized, multicenter, double-masked, parallel-group, dose-response controlled trial.

PARTICIPANTS

Total enrollment: 162 patients; cyclosporin A groups: 129 patients; vehicle group: 33 patients.

INTERVENTION

Patients instilled study medication (cyclosporin A ophthalmic emulsion 0.05%, 0.1%, 0.2%, or 0.4%, or vehicle) twice daily into both eyes for 12 weeks, followed by a 4-week posttreatment observation period.

MAIN OUTCOME MEASURES

EFFICACY

rose bengal staining, superficial punctate keratitis, Schirmer tear test, symptoms of ocular discomfort, and the Ocular Surface Disease Index (OSDI; a measure of symptom frequency and impact on vision-related functioning).

SAFETY

biomicroscopy, cyclosporin A blood levels, conjunctival microbiology, intraocular pressure, visual acuity, and monitoring of adverse events.

RESULTS

In a subset of 90 patients with moderate-to-severe keratoconjunctivitis sicca, the most significant improvements with cyclosporin A treatment were in rose bengal staining, superficial punctate keratitis, sandy or gritty feeling, dryness, and itching, with improvements persisting into the posttreatment period in some treatment groups. There was also a decrease in OSDI scores, indicating a decrease in the effect of ocular symptoms on patients' daily lives. There was no clear dose-response relationship, but cyclosporin A 0.1% produced the most consistent improvement in objective and subjective end points and cyclosporin A 0.05% gave the most consistent improvement in patient symptoms. The vehicle also performed well, perhaps because of its long residence time on the ocular surface. There were no significant adverse effects, no microbial overgrowth, and no increased risk of ocular infection in any treatment group. The highest cyclosporin A blood concentration detected was 0.16 ng/ml. All treatments were well tolerated by patients.

CONCLUSIONS

Cyclosporin A ophthalmic emulsions, 0.05%, 0.1%, 0.2%, and 0.4%, were safe and well tolerated, significantly improved the ocular signs and symptoms of moderate-to-severe dry eye disease, and decreased the effect of the disease on vision-related functioning. Cyclosporin A 0.05% and 0.1% were deemed the most appropriate formulations for future clinical studies because no additional benefits were observed with the higher concentrations.

Super-Cationic Carbon Quantum Dots Synthesized from Spermidine as an Eye Drop Formulation for Topical Treatment of Bacterial Keratitis

We have developed a one-step method to synthesize carbon quantum dots (CQD_PAs) from biogenic polyamines (PAs) as an antibacterial agent for topical treatment of bacterial keratitis (BK). CQDs synthesized by direct pyrolysis of spermidine (Spd) powder through a simple dry heating treatment exhibit a solubility and yield much higher than those from putrescine and spermine. We demonstrate that CQDs obtained from Spds (CQD_Spds) possess effective antibacterial activities against non-multidrug-resistant Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica serovar Enteritidis bacteria and also against the multidrug-resistant bacteria, methicillin-resistant S. aureus. The minimal inhibitory concentration (MIC) of CQD_Spds is ∼2500-fold lower than that of spermidine alone, demonstrating their strong antibacterial capabilities. Investigation of the possible mechanisms behind the antibacterial activities of the as-synthesized CQD_Spds indicates that the super-cationic CQD_Spds with small size (diameter ca. 6 nm) and highly positive charge (ζ-potential ca. +45 mV) cause severe disruption of the bacterial membrane. In vitro cytotoxicity, hemolysis, hemagglutination, genotoxicity, and oxidative stress and in vivo morphologic and physiologic cornea change evaluations show the good biocompatibility of CQD_Spds. Furthermore, topical ocular administration of CQD_Spds can induce the opening of the tight junction of corneal epithelial cells, thereby leading to great antibacterial treatment of S. aureus-induced BK in rabbits. Our results suggest that CQD_Spds are a promising antibacterial candidate for clinical applications in treating eye-related bacterial infections and even persistent bacteria-induced infections.

Adherence in glaucoma: objective measurements of once-daily and adjunctive medication use

PURPOSE

To determine with electronic monitoring an objective measurement of adherence in two populations of subjects: those using once-daily prostaglandin analogs as sole ocular hypotensive therapy (one-drug group) and those requiring an adjunctive medicine to the prostaglandin analog (two-drug group).

DESIGN

Single-site, open-label, nonrandomized, parallel design of 60 days.

METHODS

Sixty-two consecutive adult subjects with a diagnosis of open-angle glaucoma (OAG) or ocular hypertension: 31 were taking one drug and 31 were taking two drugs. An electronic event medication monitoring device was used to record each bottle opening. The main outcome measures were dosing errors (number of under-adherence or over-adherence events) and coverage (proportion of pharmacologic duration covered by dosing) relative to the ophthalmologist-prescribed regimen.

RESULTS

Adherence to the prostaglandins once daily was good in both groups by all measures (<or=10% of subjects with more than five dosing errors and mean coverage of 97.2% +/- 6.1%). Adherence to the second medication in the two-drug group was poorer (37% of subjects with more than five dosing errors and mean coverage of 85.6% +/- 12.6%). For the subjects using beta-adrenoceptor antagonists, 24.8% +/- 18.4% of doses were taken at less than 10-hour intervals (over-adherence).

CONCLUSIONS

The incorporation of a time component in electronic monitoring provides more information than prescription refill rate or other methods. We found that more complex dosing regimens result in poorer adherence, although once-daily drugs in a complex dosing regimen were found to have good adherence.

Vesicular systems in ocular drug delivery: an overview

The main aim of pharmacotherapeutics is the attainment of effective drug concentration at the intended site of action for a sufficient period of time to elicit a response. Poor bioavailability of drugs from ocular dosage form is mainly due to the tear production, non-productive absorption, transient residence time, and impermeability of corneal epithelium. Though the topical and localized application are still an acceptable and preferred way to achieve therapeutic level of drugs used to treat ocular disorders but the primitive ophthalmic solution, suspension, and ointment dosage form are no longer sufficient to combat various ocular diseases. This article reviews the constraints with conventional ocular therapy and explores various novel approaches, in general, to improve ocular bioavailability of the drugs, advantages of vesicular approach over these and the future challenges to render the vesicular system more effective.

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.

Penetration enhancers and ocular bioadhesives: two new avenues for ophthalmic drug delivery

This review is focused on the two avenues of development that promise a major impact on future ocular drug therapeutics: bioadhesives, including hydrogels and other agents like carbopols, polyacrylic acids, chitosan, etc., and penetration enhancers, including different surfactants, calcium chelators, etc. The capacity of some polymers to adhere to the mucin coat covering the conjunctiva and the corneal surface of the eye forms the basis for ocular mucoadhesion. These systems markedly prolong the residence time of a drug in the conjunctival sac, since clearence is now controlled by the much slower rate of mucus turnover rather than the tear turnover rate. But improving the corneal drug retention alone is inadequate in bringing about a significant improvement of drug bioavailability. Another approach consists of transiently increasing the pentration characteristics of the cornea with appropriate substances, known as penetration enhancers or absorption promoters. The main aim of this article is to give an insight into the potential application of mucoadhesives and corneal penetration enhancers for the conception of innovative opthalmic delivery appraoches, to decrease the systemic side effects, and create a more focused effect, which may be achieved with lower doses of the drug. Ophthalmic formulations based on these mucoadhesives and penetration enhancers are simple to manufacture and exhibit an excellent tolerance when administered into the cornea. The use of the former considerably prolongs the corneal contact time and the use of the latter increases the rate and amount of drug transport. The various corneal epithelial barriers along with the major routes of transport of drugs are discussed. The article includes a list of the various substances in use or under investigation for the aforementioned properties, along with their mechanisms of action. A fair appraisal of the subject with regard to these two therapeutic approaches and any expected ill effects has been made.

Hyaluronan: pharmaceutical characterization and drug delivery

Hyaluronic acid (HA), is a polyanionic polysaccharide that consists of N-acetyl-D-glucosamine and beta-glucoronic acid. It is most frequently referred to as hyaluronan because it exists in vivo as a polyanion and not in the protonated acid form. HA is distributed widely in vertebrates and presents as a component of the cell coat of many strains of bacteria. Initially the main functions of HA were believed to be mechanical as it has a protective, structure stabilizing and shock-absorbing role in the body. However, more recently the role of HA in the mediation of physiological functions via interaction with binding proteins and cell surface receptors including morphogenesis, regeneration, wound healing, and tumor invasion, as well as in the dynamic regulation of such interactions on cell signaling and behavior has been documented. The unique viscoelastic nature of hyaluronan along with its biocompatibility and nonimmunogenicity has led to its use in a number of cosmetic, medical, and pharmaceutical applications. More recently, HA has been investigated as a drug delivery agent for ophthalmic, nasal, pulmonary, parenteral, and dermal routes. The purpose of our review is to describe the physical, chemical, and biological properties of native HA together with how it can be produced and assayed along with a detailed analysis of its medical and pharmaceutical applications.

Treatment for glaucoma: adherence by the elderly

OBJECTIVES

The purpose of this study was to determine the extent of nonadherence to treatment for glaucoma among elderly patients.

METHODS

This was a retrospective cohort study of 2440 patients older than age 65 who were enrolled in the New Jersey Medicaid Program and who were newly initiated on a topical agent for the treatment of glaucoma. Two patient-specific measures of nonadherence were employed: (1) no filled prescription for any glaucoma medication over a 12-month period after the initiation of therapy and (2) number of days without therapy for glaucoma during this 12-month period.

RESULTS

By the first measure, 569 patients (23%) were found to be nonadherent. The mean number of days without therapy during the study year was 112. Factors associated with nonadherence included the use of glaucoma medication requiring more than 2 administrations per day and the presence of multiple other medications in the patient's drug regimen. Patients started on multiple glaucoma medication were more adherent than those started on a single agent. Age and sex were not found to be predictors of nonadherence.

CONCLUSIONS

Substantial nonadherence was found to be common in this population. More attention to the issue of nonadherence could result in important benefits in the preservation of sight.

Topical treatment with nerve growth factor for neurotrophic keratitis

OBJECTIVE

To evaluate the efficacy of nerve growth factor (NGF) in patients with neurotrophic keratitis.

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

Forty-five eyes of 43 consecutive patients with moderate (stage 2, n = 17) to severe (stage 3, n = 28) neurotrophic keratitis unresponsive to other nonsurgical therapies.

METHODS

After a 10-day washout with preservative-free artificial tears, 45 eyes with neurotrophic keratitis received murine NGF (200 microg/ml) every 2 hours for 2 days followed by one drop six times daily until the ulcer healed. A maintenance dose of one drop NGF (100 microg/ml) was administered four times daily for the 2 weeks subsequent to ulcer healing.

MAIN OUTCOME MEASURES

Size and depth of the ulcer or the epithelial defect, corneal sensitivity, best corrected visual acuity, side effects, and relapse of the disease in the follow-up period.

RESULTS

All patients had a complete resolution of the persistent epithelial defect (with or without an ulcer) after 12 days to 6 weeks of treatment with NGF. Patients affected by both stages of the disease demonstrated both improved corneal sensitivity and visual acuity (P<0.001). No significant differences were observed in the time to complete corneal healing between stage 2 and stage 3 patients. Hyperemia and ocular and periocular pain were side effects reported during the first days of treatment. No relapse of the disease was observed during the follow-up period, with the exception of three patients with trigeminal nerve resection, who required a single retreatment.

CONCLUSIONS

Nerve growth factor eye drops improved corneal sensitivity and promoted corneal epithelial healing in both moderate and severe neurotrophic keratitis. Although performed in an uncontrolled and nonrandomized series of patients, this therapy shows promise for the restoration of ocular surface integrity and visual function in neurotrophic corneal disease.

Ophthalmic drug delivery through contact lenses

PURPOSE

Currently available ophthalmic drug delivery systems are inefficient and may lead to side effects. To increase efficiency and reduce side effects, the authors propose disposable particle-laden soft contact lenses for ophthalmic drug delivery.

METHODS

The essential idea is to encapsulate the ophthalmic drug formulations in nanoparticles and to disperse these drug-laden particles in the lens material, such as poly-2-hydroxyethyl methacrylate (p-HEMA) hydrogels. The drug-laden p-HEMA hydrogels were synthesized by free radical solution polymerization of the monomers in presence of nanoparticles. The particle-laden hydrogels were characterized by light-transmission and electron microscopy studies. Release profiles of lidocaine, a model hydrophobic drug, were measured by UV-Vis spectrophotometry.

RESULTS

Microemulsions of hexadecane in water stabilized with a silica shell around the particles produced transparent hydrogels. Contact lenses made with particle-laden hydrogels released therapeutic levels of drug for a few days.

CONCLUSIONS

Particle-laden hydrogels are promising candidates for ophthalmic drug delivery. They are transparent and can release drugs for extended periods. The drug delivery rates can be controlled by varying the loading of nanoparticles in the gel.

Ocular release of timolol from molecularly imprinted soft contact lenses

The aim of this study was to evaluate "in vivo" the usefulness of molecular imprinting technology to obtain therapeutic soft contact lenses capable of prolonging the permanence of timolol in the precorneal area, compared to conventional contact lenses and eyedrops. Soft contact lenses (diameter 14 mm, center thickness 0.08 mm) consisted of N,N-diethylacrylamide (DEAA; main component of the matrix), methacrylic acid (MAA; functional monomer) and ethylene glycol dimethacrylate (EGDMA; cross-linker) were prepared by the conventional methodology (non-imprinted) or by applying a molecular imprinting technique using timolol as the template (imprinted ones). After washing and reloading, timolol release studies carried out in rabbits showed that the soft contact lenses made by the molecular imprinting method (34 microg dose) provided measurable timolol concentrations in the tear fluid for 2.0- and 3.0-fold longer than the non-imprinted contact lenses (21 microg dose) and eyedrops (doses of 34 and 125 microg), respectively. Furthermore, the area under the timolol concentration-time curve (AUC) was 3.3- and 8.7-fold greater for imprinted contact lenses than non-imprinted contact lenses and eyedrops, respectively. The timolol concentration of the eyedrops did not affect the precorneal residence time of drug significantly. On the other hand, timolol loading capacity of the contact lenses was improved by the molecular imprinting method; the sustaining of the drug levels in the tear fluid being proportional to the loading capacity of the contact lenses. These results indicate that imprinted soft contact lenses are promising drug devices able to provide greater and more sustained drug concentrations in tear fluid with lower doses than conventional eyedrops.

Poly(amidoamine) dendrimers as ophthalmic vehicles for ocular delivery of pilocarpine nitrate and tropicamide

The purpose of this study was to determine the influence of a controlled incremental increase in size, molecular weight and number of amine, carboxylate and hydroxyl surface groups in several series of poly(amidoamine) (PAMAM) dendrimers for controlled ocular drug delivery. The duration of residence time was evaluated after solubilization of several series of PAMAM dendrimers (generations 1.5 and 2-3.5 and 4) in buffered phosphate solutions containing 2 per thousand (w/v) of fluorescein. The New Zealand albino rabbit was used as an in vivo model for qualitative and quantitative assessment of ocular tolerance and retention time after a single application of 25 microl of dendrimer solution to the eye. The same model was also used to determine the prolonged miotic or mydriatic activities of dendrimer solutions, some containing pilocarpine nitrate and some tropicamide, respectively. Residence time was longer for the solutions containing dendrimers with carboxylic and hydroxyl surface groups. No prolongation of remanence time was observed when dendrimer concentration (0.25-2%) increased. The remanence time of PAMAM dendrimer solutions on the cornea showed size and molecular weight dependency. This study allowed novel macromolecular carriers to be designed with prolonged drug residence time for the ophthalmic route.

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.

Autologous serum eye drops for the treatment of severe dry eye in patients with chronic graft-versus-host disease

We investigated the efficacy and safety of autologous serum eye drops for the treatment of severe dry eye after allogeneic haematopoietic stem cell transplantation (SCT). A total of 14 patients (four males and 10 females; median age, 31.0 years) with severe dry eye associated with chronic graft-versus-host disease (cGVHD) were enrolled in this study. All patients were refractory to treatment with conventional artificial tears. Autologous serum eye drops, a solution made of 20% autologous serum in sterile saline, were applied 10 times per eye per day. The patients were evaluated every 4 weeks according to visual acuity, corneal sensitivity, vital staining of the ocular surface, tear dynamics, and subjective assessments of symptoms (complaints scores). The median follow-up period was 19.4 months (range: 4-41 months). After 4 weeks of treatment, significant improvement was observed in both complaint scores (from 33.7+/-12.3 to 23.6+/-10.6 points; P<0.01) and fluorescein scores (from 5.8+/-2.0 to 2.4+/-0.9 points; P<0.005). Significant improvements were observed also in rose-bengal staining and tear break-up time. In seven of the 14 patients, the responses were maintained for 6-41 months (median:19.4+/-8.3 months), while six of the other seven patients required treatment with punctal plugs in addition to autologous serum eye drops. One of these other seven patients developed eczema around the eyelids, after which the treatment was discontinued. No serious adverse events were observed. We conclude that autologous serum eye drops are safe and effective for treating severe dry eye associated with cGVHD and that more efficient control of dry eye may be achieved by the combined use of autologous serum eye drops with punctal plugs.

Microemulsions as ocular drug delivery systems: recent developments and future challenges

Eye drops are the most used dosage form by ocular route, in spite of low bioavailability and the pulsed release of the drug. However, due to their intrinsic properties and specific structures, the microemulsions are a promising dosage form for the natural defence of the eye. Indeed, because they are prepared by inexpensive processes through autoemulsification or supply of energy, and can be easily sterilized, they are stable and have a high capacity of dissolving the drugs. The in vivo results and preliminary studies on healthy volunteers have shown a delayed effect and an increase in the bioavailability of the drug. The proposed mechanism is based on the adsorption of the nanodroplets representing the internal phase of the microemulsion, which constitutes a reservoir of the drug on the cornea and should then limit their drainage.

Liposomes as an ocular delivery system for acetazolamide: in vitro and in vivo studies

The purpose of this study was to formulate topically effective controlled release ophthalmic acetazolamide liposomal formulations. Reverse-phase evaporation and lipid film hydration methods were used for the preparation of reverse-phase evaporation (REVs) and multilamellar (MLVs) acetazolamide liposomes consisting of egg phosphatidylcholine (PC) and cholesterol (CH) in the molar ratios of (7:2), (7:4), (7:6), and (7:7) with or without stearylamine (SA) or dicetyl phosphate (DP) as positive and negative charge inducers, respectively. The prepared liposomes were evaluated for their entrapment efficiency and in vitro release. Multilamellar liposomes entrapped greater amounts of drug than REVs liposomes. Drug loading was increased by increasing CH content as well as by inclusion of SA. Drug release rate showed an order of negatively charged > neutral > positively charged liposomes, which is the reverse of the data of drug loading efficiency. Physical stability study indicated that approximately 89%, 77%, and 69% of acetazolamide was retained in positive, negative, and neutral MLVs liposomal formulations up to a period of 3 months at 4 degrees C. The intraocular pressure (IOP)-lowering activity of selected acetazolamide liposomal formulations was determined and compared with that of plain liposomes and acetazolamide solution. Multilamellar acetazolamide liposomes revealed more prolonged effect than REVs liposomes. The positively charged and neutral liposomes exhibited greater lowering in IOP and a more prolonged effect than the negatively charged ones. The positive multilamellar liposomes composed of PC:CH:SA (7:4:1) molar ratio showed the maximal response, which reached a value of -7.8 +/- 1.04 mmHg after 3 hours of topical administration.

Effects of different concentrations of atropine on controlling myopia in myopic children

Although 1% atropine effectively slows myopia progression, it is associated with adverse effects, including photophobia, blurred near vision, and poor compliance. We investigated whether lower doses of atropine would control myopia progression. One hundred and eighty-six children, from 6 to 13 years of age, were treated each night with different concentrations of atropine eye drops or a control treatment for up to 2 years. The mean myopic progression in each of the groups was 0.04 +/-0.63 diopter per year (D/Y) in the 0.5% atropine group, 0.45+/-0.55 D/Y in the 0.25% atropine group, and 0.47+/-0.91 D/Y in the 0.1% atropine group. All atropine groups showed significantly less myopic progression than the control group (1.06+/-0.61 D/Y) (p<0.01). Our study also showed that 61% of students in the 0.5% atropine group, 49% in the 0.25% atropine group and 42% in the 0.1% atropine group had no myopic progression. However, 4% of children in the 0.5% atropine group, 17% in the 0.25% atropine group, and 33% in the 0.1% atropine group still had fast myopic progression (>-1.0 D/Y). In contrast, only 8% of the control group showed no myopic progression and 44% had fast myopic progression. These results suggest that all three concentrations of atropine had significant effects on controlling myopia; however, treatment with 0.5% atropine was the most effective.

Thermosetting gels with modulated gelation temperature for ophthalmic use: the rheological and gamma scintigraphic studies

For ophthalmic drug delivery, Pluronic F127 solutions have a phase transition temperature too low for them to be instilled into the eye at room temperature. Refrigerator storage is usually required to make administration easier, whereas the potential irritation of cold to the sensitive ocular tissues may result in poor topical bioavailability. The purpose of this study is to develop a thermosetting gel with a suitable phase transition temperature by combining Pluronic analogs and to examine the influence of incorporating mucoadhesive polysaccharide, sodium hyaluronate (HA-Na), on the ocular retention of the gel. Dynamic rheological method and single photon emission computing tomography (SPECT) technique were used to ex/in vivo evaluate the thermosetting gels, respectively. An optimized formulation containing 21% F127 and 10% F68 increased the phase transition temperature by 9 degrees C as evaluated by elasticity modulus compared to that of individual 21% F127 solution. Rheological behaviors of the Pluronic solutions showed that the combined Pluronic formulation was free flowing liquid below 25 degrees C and converted to a firm gel under the physiological condition. Furthermore, this formulation possessed the highest viscosity both before and after tear dilution at 35 degrees C. Gamma scintigraphic data demonstrated that the clearance of the thermosetting gel labeled with 99mTc-DTPA was significantly delayed with respect to the phosphate buffered solution, and at least a threefold increase of the corneal residence time was achieved. However, no further improvement in the ocular retention was observed when adding HA-Na into the thermosetting gel due to the substantially decreased gel strength.

Ocular preparations: the formulation approach

The main aim of pharmacotherapeutics is the attainment of an effective drug concentration at the intended site of action for a sufficient period of time to elicit the response. A major problem being faced in ocular therapeutics is the attainment of an optimal concentration at the site of action. Poor bioavailability of drugs from ocular dosage forms is mainly due to the tear production, non-productive absorption, transient residence time, and impermeability of corneal epithelium. This article reviews: (1) the barriers that decrease the bioavailability of an ophthalmic drug; (2) the objectives to be considered in producing optimal formulations; and (3) the approaches being used to improve the corneal penetration of a drug molecule and delay its elimination from the eye. The focus of this review is on the recent developments in topical ocular drug delivery systems, the rationale for their use, their drug release mechanism, and the characteristic advantages and limitations of each system. In addition, the review attempts to give various analytical procedures including the animal models and other models required for bioavailability and pharmacokinetic studies. The latter can aid in the design and predictive evaluation of newer delivery systems. The dosage forms are divided into the ones which affect the precorneal parameters, and those that provide a controlled and continuous delivery to the pre- and intraocular tissues. The systems discussed include: (a) the commonly used dosage forms such as gels, viscosity imparting agents, ointments, and aqueous suspensions; (b) the newer concept of penetration enhancers, phase transition systems, use of cyclodextrins to increase solubility of various drugs, vesicular systems, and chemical delivery systems such as the prodrugs; (c) the developed and under-development controlled/continuous drug delivery systems including ocular inserts, collagen shields, ocular films, disposable contact lenses, and other new ophthalmic drug delivery systems; and (d) the newer trends directed towards a combination of drug delivery technologies for improving the therapeutic response of a non-efficacious drug. The fruitful resolution of the above-mentioned technological suggestions can result in a superior dosage form for both topical and intraocular ophthalmic application.