Dual drug delivery from vitamin E loaded contact lenses for glaucoma therapy

Glaucoma patients frequently instill eye drops multiple times each day, which is a cause for reduced compliance. Additionally, eye drops suffer from other limitations including low bioavailability, which can lead to side effects. We propose to develop drug-eluting contact lenses for managing glaucoma with increased bioavailability and improved compliance.Contact lenses are developed for extended simultaneous release of timolol and dorzolamide, both of which are commonly prescribed hydrophilic drugs. The extended release is achieved by loading lenses with vitamin E barriers. In vitro release studies are performed with control and vitamin E loaded lenses for both drugs loaded separately and then together in the same lens. The safety and efficacy of combination therapy by contacts are demonstrated in a Beagle model of glaucoma.Simultaneous loading of timolol and dorzolamide increases the release duration of both drugs. Also vitamin E incorporation is highly effective in increasing the release durations of both drugs to about 2-days. The lenses loaded with both drugs exhibited superior IOP reduction compared to eye drops with about 6-fold lower drug loading. More importantly, combination therapy by continuous wear of vitamin E loaded contact for 2-days, followed by a new set of contacts for another two days, reduced IOP during the 4 days of wear time and for another 8 days after removal of the contacts.Vitamin E loading is very effective for providing combination therapy by contact lenses due to the increase in release durations of several drugs. The contact lens based therapy reduces IOP with lower drug dose compared to eye drops and may significantly improve the compliance as the effect of the therapy lasts significantly longer than the wear-duration.     

Molecularly imprinted therapeutic contact lenses

Importance of the field: There exists a considerable unmet need for more efficacious delivery of ocular therapeutics. Contact lenses have been developed with high loading and controllable sustained release to overcome limited patient compliance and significant ocular transport limitations. This can best be achieved by extending and controlling the residence time of drugs on the eye surface and thereby limiting drug loss by lacrimation, drainage and non-productive absorption.

Areas covered in the review: Within hydrogels, molecular imprinting can be used to create memory for template molecules embedded within a flexible macromolecular network. Control in therapeutic loading and delay of release have been demonstrated with careful attention to the functional monomer/template ratio, the diversity of functional monomers, and the polymer backbone and network structure. Experimental work has also confirmed that macromolecular memory and not structural differences or phenomena are responsible for delayed drug release kinetics compared with non-imprinted systems. A therapeutically relevant amount of drug can be loaded for release to occur over multiple days, which allows the technique to be applied to daily-wear and extended-wear contact lenses.

What the reader will gain: The focus of this article is to review the emerging field of molecularly imprinted contact lenses and highlight significant accomplishments, trends, as well as future strategies and directions.

Take home message: In the past 8 years, molecular imprinting has been used to produce therapeutic contact lenses with enhanced loading and delayed release. Progress in the field has mostly included low-molecular-weight therapeutics such as anti-glaucoma, antihistamine, antibiotic and anti-inflammatory therapeutics used to treat anterior eye disorders. Recently, high molecular weight comfort molecules have also been successfully demonstrated. Current methods can produce lenses of suitable thickness, water content, and mechanical and optical properties compared with commercial lenses on the market today.     

Castor oil and mineral oil nanoemulsion: development and compatibility with a soft contact lens

Abstract

Context: The non-invasive ophthalmic therapy has a drawback: low residence time in the eye socket. Nanoparticles and contact lenses have been studied as promising ocular drug delivery systems.

Objective: To develop a nanoemulsion and evaluate its compatibility with a soft contact lens as a potential strategy for ocular delivery.

Materials and methods: The formulations were developed by spontaneous emulsification and fully characterized. Two drops of nanoemulsion were instilled on the surface of a commercial contact lens and its transparency was measured using a UV-Vis spectrophotometer. Before and after the instillation of the drops, the morphology (scanning electron microscopy – SEM) and ion permeability of the lenses were analyzed.

Results: The formulations had a mean particle size of 234?nm, polydispersity below 0.16, zeta potential of ?8.56?±?3.49?mV, slightly acid pH, viscosity ≈1.2?mPa?s^?1 and spherical-shaped particles. Nanoemulsion was non-irritant (hen’s egg test-chorioallantoic membrane), which was confirmed by the cytotoxicity studies in the SIRC cell cultures. After instillation, SEM analysis showed nanodroplets inside and on the surface of the lenses, although their transparency remained near 100%. No significant differences were found between lens ion permeability coefficients before and after instillation.

Conclusions: Formulations presented appropriate physicochemical characteristics and suitability for ocular application. The contact lens remained transparent and ion-permeable after association with the formulation.     

Controlled release of betamethasone from vitamin E-loaded silicone-based soft contact lenses

Context: Betamethasone (BMZ) is an effective drug which is commonly used as an eye drop for the management of ophthalmic inflammations. Due to low ocular bioavailability, it is necessary to prepare and optimize an ocular drug delivery system for BMZ.

Objective: In this study we tried to use vitamin E diffusion barrier for sustaining BMZ release.

Materials and methods: Three commercial contact lenses were soaked in vitamin E solutions and swelling percentage, diameter, transmittance, binding capacity and release amount and time were evaluated in comparison with non-vitamin E-loaded pure lenses.

Results: The results showed that vitamin E significantly decreased water content of contact lenses whereas, increased the lens diameter in both dry and wet states. It effectively blocked UV radiation which is harmful for the eye surface while had no significant effect on visible transmittance. BMZ loading capacity enhanced and release rate remarkably decreased after using vitamin E as a hydrophobic diffusion barrier.

Discussion and conclusions: This study revealed that vitamin E can be applied as a hydrophobic diffusion barrier for controlling and sustaining BMZ release from silicone-based soft contact lenses into the lachrymal fluid. It can also protect eye tissues as an antioxidant by blocking the UV radiation.     

Experimental studies on soft contact lenses for controlled ocular delivery of pirfinedone: in vitro and in vivo

Context: Pirfinedone (PFD) is a novel agent which has the potential to prevent scarring in the eyes. The 0.5% PFD eye drops exhibits poor bioavailability. Whereas, the feasibility of using contact lens as ocular drug delivery device initiated novel possibilities.

Objective: To evaluate the delivery of PFD by soft contact lens (SCL) in vivo, we screened the most suitable lens material for PFD among various commercially available SCL materials in vitro.

Material and methods: Firstly, 11 different SCLs (?1.00 diopter) were respectively soaked in 2?ml of 0.05% PFD-loading solution for 24?h to fully absorb drug, and then placed in fresh phosphate buffered saline (PBS) to release the drug. PFD concentration in PBS was determined by ultraviolet absorbance at 310?nm. Secondly, by immersing in 2?ml of 0.5% PFD eye drops for 24?h, the polymacon lens (0.00 diopter) was then placed on the cornea of New Zealand rabbits. PFD concentrations were detected by high performance liquid chromatography (HPLC) in tears, aqueous humor, conjunctiva, cornea, and sclera at different time points.

Results: PFD showed some affinity for pHEMA-based lenses and the polymacon lens more slowly released more amount of PFD than any other lens in vitro (p < 0.001). Compared with eye drops, drug-loaded SCLs greatly enhanced the retention time and concentrations of PFD in cornea and aqueous humor and consequently improved the bioavailability of PFD.

Conclusion: Polymacon-based SCL is probably a promising vehicle to be an effective ophthalmic delivery system for PFD.     

In vitro and in vivo evaluation of ketotifen fumarate-loaded silicone hydrogel contact lenses for ocular drug delivery

The purpose of this work was to evaluate the usefulness of silicone hydrogel contact lenses loaded with ketotifen fumarate for ocular drug delivery. First, silicone contact lenses were prepared by photopolymerization of bitelechelic methacrylated polydimethylsiloxanes macromonomer, 3-methacryloxypropyltris(trimethylsiloxy)silane, and N,N-dimethylacrylamide using ethylene glycol dimethacrylate as a cross-linker and Darocur 1173 as an initiator followed by surface plasma treatment. Then, the silicone hydrogel matrices of the contact lenses were characterized by equilibrium swelling ratio (ESR), tensile tests, ion permeability, and surface contact angle. Finally, the contact lenses were loaded with ketotifen fumarate by pre-soaking in drug solution to evaluate drug loading capacity, in vitro and in vivo release behavior of the silicone contact lenses. The results showed that ESR and ion permeability increase, and the surface contact angle and tensile strength decreased with the increase of DMA component in the silicone hydrogel. The drug loading and in vitro releases were dependent on the hydrogel composition of hydrophilic/hydrophobic phase of the contact lenses. In rabbit eyes, the pre-soaked contact lenses sustained ketotifen fumarate release for more than 24?h, which leads to a more stable drug concentration and a longer mean retention time in tear fluid than that of eye drops of 0.05%.     

Application of lipid nanoparticles to ocular drug delivery

ABSTRACT

Introduction: Although eye drops are widely used as drug delivery systems for the anterior segment of the eye, they are also associated with poor drug bioavailability due to transient contact time and rapid washout by tearing. Moreover, effective drug delivery to the posterior segment of the eye is challenging, and alternative routes of administration (periocular and intravitreal) are generally needed, the blood–retinal barrier being the major obstacle to systemic drug delivery.

Areas covered: Nanotechnology, and especially lipid nanoparticles, can improve the therapeutic efficiency, compliance and safety of ocular drugs, administered via different routes, to both the anterior and posterior segment of the eye. This review highlights the main ocular barriers to drug delivery, as well as the most common eye diseases suitable for pharmacological treatment in which lipid nanoparticles have proved efficacious as alternative delivery systems.

Expert opinion: Lipid-based nanocarriers are among the most biocompatible and versatile means for ocular delivery. Mucoadhesion with consequent increase in pre-corneal retention time, and enhanced permeation due to cellular uptake by corneal epithelial cells, are the essential goals for topical lipid nanoparticle delivery. Gene delivery to the retina has shown very promising results after intravitreal administration of lipid nanoparticles as non-viral vectors.     

Chloramphenicol/sulfobutyl ether-β-cyclodextrin complexes in an ophthalmic delivery system: prolonged residence time and enhanced bioavailability in the conjunctival sac

Objective: Conventional chloramphenicol (CHL) eye drops are widely used anti-infection formulations for acute bacterial conjunctivitis. However, the therapeutic effects are limited by insufficient concentration in the conjunctival sac. Hence, the objective of this study is to formulate and develop novel CHL eye drops with improved topical concentrations by increasing the solubility and decreasing the transcorneal penetration.

Research design and methods: CHL was included in the sulfobutyl ether-β-cyclodextrin (SBE-β-CD) using the freeze-drying method. Eye drops containing CHL/SBE-β-CD complexes were prepared and evaluated for in vitro and in vivo studies.

Results: The formation of CHL/SBE-β-CD inclusion was confirmed by DSC, XRD, NMR, and SEM. The aqueous solubility of CHL was significantly enhanced, and the drug transcorneal penetration was inhibited after inclusion. The CHL/SBE-β-CD displayed sustained release profiles. The tear fluid elimination kinetic study showed that the CHL/SBE-β-CD eye drops had better ability to prolong the residence time, and significantly increase CHL concentration in the conjunctival sac. Besides, it was shown that CHL/SBE-β-CD eye drops were nonirritating to rabbits’ eyes.

Conclusions: The SBE-β-CD inclusions offer a potential alternative strategy for ocular administration of poorly water-soluble drugs in the conjunctival sac.     

Tafluprost for glaucoma

Introduction: Lowering intraocular pressure (IOP) is, at present, the only therapeutic approach to the treatment of glaucoma. Good compliance is essential in every chronic therapy; therefore, the development of IOP-lowering eye drops that are well tolerated and have an easy administration schedule is essential for the treatment of glaucoma. Prostaglandins are a first-choice drug class for the treatment of glaucoma.

Areas covered: This review provides a background on tafluprost, a newly synthesized prostaglandin analogue, and summarizes the existing data on its efficacy and safety, including comparative data with the other prostaglandin derivatives now available on the market. A review of the literature was performed.

Expert opinion: Current research focuses not only on the efficacy of the drugs but also on their tolerability. The importance of obtaining good compliance by the patient is increasingly relevant; therefore, new formulations are studied to provide fewer side effects and an easier schedule. Tafluprost is a new prostaglandin analogue that has been marketed in some European countries and in Japan for more than 2 years and was recently (July 2009) approved in 21 countries. Besides a well-demonstrated IOP-lowering effect, tafluprost is the first topical prostaglandin available as a preservative-free formulation.     

Formulation approaches in enhancement of patient compliance to oral drug therapy

Introduction: Disease management of outdoor patients is mainly affected by patient compliance to the drug therapy, which in turn is governed by patient convenience. Failure to follow through with a treatment decision is one of the biggest causes of unsuccessful medical care. At present, different formulation options are available for various drugs, and hence, the decision is based on the most convenient dosage form for the patient, along with optimum therapeutic benefits.

Areas covered: This paper reviews various available formulation approaches, in the hope of improving patient convenience, compliance and the overall outcome of oral drug therapy.

Expert opinion: While parenterals are valued for their speed and efficiency of delivery, these systems generally score low on patient satisfaction surveys. The oral route is the preferred route for drug delivery, although it renders multiple obstacles to formulate a patient-convenient platform, such as unfavorable taste and swallowing difficulties. Transdermal drug delivery also provides high patient satisfaction, but is effective only for the delivery of smaller, lipophilic molecules. The increasing development of biopharmaceutical therapies renders an increasing number of challenges for formulation scientists to develop a more patient-convenient means of drug delivery.     

Improved penetration of aminoglycosides and fluoroquinolones into the aqueous humour of patients by means of Acuvue contact lenses

Objectives: In order to improve the penetration of topically applied drugs in ophthalmology, the suitability of hydrophilic contact lenses (Acuvue, Vistacon, power −1.0 D) as a drug delivery system for antibiotics was tested. A prospective study was undertaken to determine the transcorneal penetration of five topically applied aminoglycosides and fluoroquinolones into the aqueous humour of patients. Methods: Two hundred and sixty-five patients undergoing cataract extraction received 0.3% gentamicin, kanamycin, tobramycin, ciprofloxacin or ofloxacin solution by two different modes of administration: either as eye drops (nine drops every 15 min, starting 2 h prior to surgery) or by means of a drug delivery system (Acuvue contact lenses soaked for 1 h in eye drop solution without preservatives, 1–5 h prior to surgery). At the beginning of cataract extraction, 50–100 μl aqueous fluid was aspirated from the anterior chamber and immediately stored at −80 °C. Antibiotic concentrations were measured using fluorescence polarisation immuno-assays (aminoglycosides) or high-performance liquid chromatography (fluoroquinolones). Results: After soaking for 1 h in 0.3% eye drop solutions, Acuvue contact lenses released about 190–250 μg aminoglycoside and ofloxacin and 1000 μg ciprofloxacin. These amounts are considerably lower or in the same order of magnitude than obtained with application of eye drops (1350 μg). From the aminoglycosides tested, only gentamicin and tobramycin, but not kanamycin, were able to penetrate into the aqueous humour of patients. After the wearing of antibiotic-soaked lenses, mean aqueous humour concentrations were higher than after the use of eye drops. This difference reached significance in tobramycin (1.09 (1.30) μg · ml⁻¹ vs 0.49 (0.79) μg · ml⁻¹), ciprofloxacin (1.23 (0.60) μg · ml⁻¹ vs 0.38 (0.33) μg · ml⁻¹) and ofloxacin (5.55 (2.53) μg · ml⁻¹ vs 0.56 (0.37) μg · ml⁻¹). The percentage of patients with aqueous humour concentration above the MIC₉₀ of Staphylococcus epidermidis, the most common cause of postoperative endophthalmitis, was 92% and 100% after wearing ciprofloxacin- or ofloxacin-soaked lenses, respectively. Conclusion: Gentamicin and tobramycin penetrated into the aqueous humour of patients, whereas kanamycin was not able to overcome the corneal barrier. Acuvue contact lenses soaked in 0.3% eye drop solutions can release sufficient amounts of gentamicin, ciprofloxacin and ofloxacin to produce bacteriostatic concentrations in the humor aquosus. Acuvue contact lenses can be recommended as a drug delivery system for fluoroquinolones. Received: 15 October 1998 / Accepted in revised form: 16 December 1998     

The potential of magneto-electric nanocarriers for drug delivery

Introduction: The development and design of personalized nanomedicine for better health quality is receiving great attention. In order to deliver and release a therapeutic concentration at the target site, novel nanocarriers (NCs) were designed, for example, magneto-electric (ME) which possess ideal properties of high drug loading, site-specificity and precise on-demand controlled drug delivery.

Areas covered: This review explores the potential of ME-NCs for on-demand and site-specific drug delivery and release for personalized therapeutics. The main features including effect of magnetism, improvement in drug loading, drug transport across blood?brain barriers and on-demand controlled release are also discussed. The future directions and possible impacts on upcoming nanomedicine are highlighted.

Expert opinion: Numerous reports suggest that there is an urgent need to explore novel NC formulations for safe and targeted drug delivery and release at specific disease sites. The challenges of formulation lie in the development of NCs that improve biocompatibility and surface modifications for optimum drug loading/preservation/transmigration and tailoring of electrical–magnetic properties for on-demand drug release. Thus, the development of novel NCs is anticipated to overcome the problems of targeted delivery of therapeutic agents with desired precision that may lead to better patient compliance.     

Controlled transscleral drug delivery formulations to the eye: establishing new concepts and paradigms in ocular anti-inflammatory therapeutics and antibacterial prophylaxis

Importance of the field: The use of topical agents poses unique and challenging hurdles for drug delivery. Topical steroids effectively control ocular inflammation, but are associated with the well-recognized dilemma of patient compliance. Although administration of topical antimicrobials as prophylaxis is acceptable among ophthalmologists, this common practice has no sound evidence base. Developing a new antimicrobial agent or delivery strategy with enhanced penetration by considering the anatomical and physiological constraints exerted by the barriers of the eye is not a commonly perceived strategy. Exploiting the permeability of the sclera, subconjunctival routes may offer a promising alternative for enhanced drug delivery and tissue targeting.

Area covered in this review: Ocular drug delivery strategies were reviewed for ocular inflammation and infections clinically adopted for newer class of antimicrobials, which use a multipronged approach to limit risks of endophthalmitis.

What the reader will gain: The analysis substantiates a new transscleral drug delivery therapeutic approach for cataract surgery.

Take home message: A new anti-inflammatory and anti-infective paradigm that frees the patient from the nuisance of topical therapeutics is introduced, opening a large investigative avenue for future improved therapies.     

Engineering of polymer–surfactant nanoparticles of doxycycline hydrochloride for ocular drug delivery

Abstract

Context: Physiologic barriers of the eye, short precorneal drug residence time and poor corneal penetration are the few reasons for reduced ocular bioavailability.

Objective: This study was aimed to develop novel polymer–surfactant nanoparticles of hydrophilic drug doxycycline hydrochloride (DXY) to improve precorneal residence time and drug penetration.

Materials and methods: Nanoparticles were formulated using emulsion cross-linking method and the formulation was optimized using factorial design. The prepared formulation was characterized for particle size, ζ potential, encapsulation efficiency, in vitro drug release and ex vivo drug diffusion studies. The antibacterial activity studies were also carried out against Escherichia coli and Staphylococcus aureus using the cup-plate method. In vivo eye irritation study was carried out by a modified Draize test in rabbits.

Results and discussion: The particle size was found to be in the range of 331–850?nm. About 45–80% of the drug was found to be encapsulated in the nanoparticles. In vitro release demonstrated sustained release profile. Lower flux values in case of nanoparticles as compared to DXY pure drug solution in ex vivo diffusion studies confirmed the sustained release. The nanoparticles were found to be significantly effective (p?<?0.001) than DXY aqueous solution due to sustained release of doxycycline from nanoparticles in both the E. coli and S. aureus strains. The formulation was found to be stable over entire stability period.

Conclusion: The developed formulation is safe and suitable for sustained ocular drug delivery.     

Evolving paradigm in the management of allergic rhinitis-associated ocular symptoms: role of intranasal corticosteroids

ABSTRACT

Background: Along with nasal symptoms, ocular symptoms such as itching, tearing, and redness are common, bothersome components of the allergic rhinitis (AR) profile. Treatment of the patient with ocular allergy symptoms should take into account a variety of factors, including severity of symptoms, convenience/compliance issues, and patient preferences.

Objectives: To review from the primary care perspective the epidemiology, pathophysiology, and management of ocular symptoms associated with AR, and to evaluate the emerging role of intranasal corticosteroids (INSs).

Findings: A search of the PubMed database identified clinical trials that assessed efficacy of agents in reducing ocular allergy symptoms. Internet searches identified further information including data on over-the-counter agents for treatment of ocular symptoms. Searches were conducted using search terms such as pathophysiology, epidemiology, ocular allergy, quality of life, drug class, and drug names. Primary care physicians are often the first point of contact for patients with seasonal AR (SAR) or perennial AR (PAR) symptoms. Ocular allergy associated with SAR and PAR (seasonal and perennial allergic conjunctivitis, respectively) is characterized by both early- and late-phase reactions, with symptoms often persisting long after allergen exposure. Non-pharmacologic measures such as allergen avoidance, use of artificial tears, and cool compresses are pertinent for all ocular allergy sufferers, but may not afford adequate symptom control. Pharmacotherapy options have traditionally included topical ophthalmic products for cases of isolated ocular symptoms, and oral antihistamines for patients with both nasal and ocular symptoms. However, this paradigm is changing with new evidence regarding the efficacy of INSs in reducing ocular symptoms. A number of meta-analyses and individual studies, most of which studied ocular symptoms as secondary variables, have demonstrated the ocular effects of INSs versus topical and oral antihistamines. Additional prospective studies on this topic are encouraged to provide further evidence for these findings.

Conclusions: In light of their well-established efficacy in reducing nasal allergy symptoms, INSs offer a compre­hensive treatment option in patients with nasal and ocular symptoms. Oral antihistamines and/or topical eye drops may also be necessary depending on symptom control.     

Stents as a platform for drug delivery

Introduction: Drug delivery stents have proved their efficacy at preventing coronary restenosis and their potential in treating the occlusion or stricture of other body passageways, such as peripheral vessels and alimentary canals. The drug delivery systems on such stent platforms contribute to this improved therapeutic efficacy by providing improved drug delivery performance, along with reduced concerns encountered by current stents (e.g., in-stent restenosis, late thrombosis and delayed healing).

Areas covered: A wide variety of drug delivery stents (metallic drug-eluting stents, absorbable drug-eluting stents, and polymer-free drug-eluting stents for coronary and other applications) that are commercially available or under investigation are collected and summarized in this review, with emphasis on their drug delivery aspects. This review also gives insights into the progression of stent-based drug delivery strategies for the prevention of stent-related problems, or the treatment of local diseases. In addition, a critical analysis of the advantages and challenges of such strategies is provided.

Expert opinion: With an in-depth understanding of drug properties, tissue/organ biology and disease conditions, stent drug delivery systems can be improved further, to endow the stents with better efficacy and safety, along with lower toxicity. There is also a great need for stents that can simultaneously deliver multiple drugs, to treat complex diseases from multiple aspects, or to treat several diseases at the same time. Drug release kinetics greatly determines the stent performance, thus effective strategies should also be developed to achieve customized kinetics.     

In situ gel systems as ‘smart’ carriers for sustained ocular drug delivery

Introduction: In situ gel systems refer to a class of novel delivery vehicles, composed of natural, semisynthetic or synthetic polymers, which present the unique property of sol–gel conversion on receipt of biological stimulus.

Areas covered: The present review summarizes the latest developments in in situ gel technology, with regard to ophthalmic drug delivery. Starting with the mechanism of ocular absorption, the review expands on the fabrication of various polymeric in situ gel systems, made up of two or more polymers presenting multi-stimuli sensitivity, coupled with other interesting features, such as bio-adhesion, enhanced penetration or sustained release. Various key issues and challenges in this area have been addressed and critically analyzed.

Expert opinion: The advent of in situ gel systems has inaugurated a new transom for ‘smart’ ocular delivery. By virtue of possessing stimuli-responsive phase transition properties, these systems can easily be administered into the eye, similar to normal eye drops. Their unique gelling properties endow them with special features, such as prolonged retention at the site of administration, followed by sustained drug release. Despite the superiority of these systems as compared with conventional ophthalmic formulations, further investigations are necessary to address the toxicity issues, so as to minimize regulatory hurdles during commercialization.     

Microrobots: a new era in ocular drug delivery

Introduction: Ocular microrobots have the potential to change the way in which we treat a variety of diseases at the anterior and the posterior segments of the eye. Wireless manipulation and positioning of drug delivery magnetic millimeter and submillimeter platforms into the eye constitute a potential route for minimally invasive targeted therapy. However, the field is still in its infancy and faces challenges related to the fabrication, control an interaction with complex biological environments.

Areas covered: This review briefly introduces the complex anatomy and physiology of the eye, which renders limitations to the current treatments of ocular diseases. The topical administration of eye drops, intravitreal injections and drug delivery implants is briefly mentioned together with their drawbacks. The authors also analyze the minimally invasive microrobotic approach as an alternative method and report the recent advancements in the fabrication, control, manipulation and drug delivery.

Expert opinion: Although microrobotics is a young field, a significant amount of work has been developed to face different challenges related to the minimally invasive manipulation of microdevices in the eye. Current research is already at the state of in vivo testing for systems and their biocompatibility. It is expected that the general concepts acquired will soon be applied for specific interventions, especially for posterior eye pathologies.     

Formulation and development of taste masked fast-disintegrating tablets (FDTs) of Chlorpheniramine maleate using ion-exchange resins

Context: Masking of bitter taste of drug for better patient compliance.

Objective: The objective of this research was to mask the bitter taste of Chlorpheniramine maleate using cation exchange resins.

Materials and methods: Different cation exchange resins were used for taste masking. The drug resin complexes (DRC) were prepared by batch process. Complexes of ion-exchange resin and Chlorpheniramine maleate were prepared by taking drug: resin ratios 1:1, 1:2, 1: 3 and 1:4 (w/w). The optimum drug: resin ratio and the time required for maximum complexation was determined. The drug resinates were evaluated for the drug content, taste, drug release, FTIR, DSC and X-ray diffraction (PXRD).

Results and discussion: The X-ray diffraction study confirmed the monomolecularity of entrapped drug in the resin beads. The taste evaluation depicted the successful taste masking of Chlorpheniramine maleate with DRCs. Fast disintegrating tablets (FDTs) were developed depending upon percent complexation, release study at salivary and gastric pH, taste evaluation; Chlorpheniramine maleate: Indion-234 complex of ratio 1:2 was used to develop and formulate FDTs. The drug release of 94.77% in 30?min was observed from FDTs.

Conclusion: The Effective taste masking can be obtained from DRC that can be formulated as FDTs for better patient compliance.     

Chitosan-based gastroretentive floating drug delivery technology: an updated review

Introduction: Gastroretentive floating drug delivery systems have emerged as efficient approaches for enhancing the bioavailability and controlled delivery of various therapeutic agents. Significant advancements exploiting chitosan have been made worldwide, in order to investigate these systems according to patient requirements, both in terms of therapeutic efficacy as well as patient compliance. Such systems precisely control the release rate of the target drug to a specific site, which facilitates an enormous impact on health care.

Areas covered: Different novel strategies have been undertaken for the development of various gastric floating dosage forms utilizing chitosan as a promising excipient. The present paper is an earnest attempt to provide new insights on various physicochemical and biological characteristics of chitosan, along with its potential applications in a wide array of biomedical approaches. Numerous and significant research findings in the vistas of chitosan-based gastroretentive floating drug delivery technology are also discussed.

Expert opinion: Chitosan has been considered as a unique and efficacious agent possessing a myriad spectrum of desired characteristics. It is emphasized that recent scientific advancements in the use of this excipient as a carrier will yield new generation gastroretentive drug delivery systems, with better pharmacotherapeutic interventions. Further studies are required to unveil the hidden beneficial properties of chitosan and its derivatives, to obtain newer delivery systems which may hold tremendous prospects in the near future.