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A Comprehensive Review on the Role of Polymers in Ocular Drug Delivery

Paramjot, Wadhwa S, Sharma A, Singh SK, Vishwas S, Kumar R, et al.

Curr Drug Deliv, 2024;21(1):16-37.
PMID: 36627785 DOI: 10.2174/1567201820666230110140312

Amongst different routes of drug delivery systems, ophthalmic drug delivery still requires a careful investigation and strict parameter measurements because the eyes are one of the most sensitive parts of the body and require special attention. The conventional systems for eyes lead to rapid elimination of formulation and hence very small contact time on the ocular epithelium. The current review article covers various types of polymers used in ocular drug delivery along with their applications/ limitations. Polymers are widely used by researchers in prodrug techniques and as a penetration enhancer in ocular delivery. This article covers the role and use of different polymeric systems which makes the final formulation a promising candidate for ophthalmic drug delivery. The researchers are still facing multiple challenges in order to maintain the therapeutic concentration of the drug in the eyes because of its complex structure. There are several barriers that further restrict the intraocular entry of the drug. In order to remove/reduce such challenges, these days various types of polymers are used for ocular delivery in order to develop different drug carrier systems for better efficacy and stability. The polymers used are highly helpful in increasing residence time by increasing the viscosity at the ocular epithelium layer. Such preparations also get easily permeated in ocular cells. The combination of different polymeric properties makes the final formulation stable with prolonged retention, high viscosity, high permeability, and better bioavailability, making the final formulation a promising candidate for ocular drug delivery.

Matched MeSH terms: Administration, Ophthalmic
In situ forming phase-inversion implants for sustained ocular delivery of triamcinolone acetonide

Sheshala R, Hong GC, Yee WP, Meka VS, Thakur RRS

Drug Deliv Transl Res, 2019 04;9(2):534-542.
PMID: 29484530 DOI: 10.1007/s13346-018-0491-y

The objectives of this study were to develop biodegradable poly-lactic-co-glycolic acid (PLGA) based injectable phase inversion in situ forming system for sustained delivery of triamcinolone acetonide (TA) and to conduct physicochemical characterisation including in vitro drug release of the prepared formulations. TA (at 0.5%, 1% and 2.5% w/w loading) was dissolved in N-methyl-2-pyrrolidone (NMP) solvent and then incorporated 30% w/w PLGA (50/50 and 75/25) polymer to prepare homogenous injectable solution. The formulations were evaluated for rheological behaviour using rheometer, syringeability by texture analyser, water uptake and rate of implant formation by optical coherence tomography (OCT) microscope. Phase inversion in situ forming formulations were injected into PBS pH 7.3 to form an implant and release samples were collected and analysed for drug content using a HPLC method. All formulations exhibited good syringeability and rheological properties (viscosity: 0.19-3.06 Pa.s) by showing shear thinning behaviour which enable them to remain as free-flowing solution for ease administration. The results from OCT microscope demonstrated that thickness of the implants were increased with the increase in time and the rate of implant formation indicated the fast phase inversion. The drug release from implants was sustained over a period of 42 days. The research findings demonstrated that PLGA/NMP-based phase inversion in situ forming implants can improve compliance in patient's suffering from ocular diseases by sustaining the drug release for a prolonged period of time and thereby reducing the frequency of ocular injections.

Matched MeSH terms: Administration, Ophthalmic
In Situ Gelling Ophthalmic Drug Delivery System: An Overview and Its Applications

Sheshala R, Kok YY, Ng JM, Thakur RR, Dua K

Recent Pat Drug Deliv Formul, 2015;9(3):237-48.
PMID: 26205681

Ophthalmic drug delivery system is very interesting and challenging due to the normal physiologically factor of eyes which reduces the bioavailability of ocular products. The development of new ophthalmic dosage forms for existing drugs to improve efficacy and bioavailability, patient compliance and convenience has become one of the main trend in the pharmaceuticals industry. The present review encompasses various conventional and novel ocular drug delivery systems, methods of preparation, characterization and recent research in this area. Furthermore, the information on various commercially available in situ gel preparations and the existing patents of in situ drug delivery systems i.e. in situ gel formation of pectin, in situ gel for therapeutic use, medical uses of in situ formed gels and in situ gelling systems as sustained delivery for front of eye are also covered in this review.

Matched MeSH terms: Administration, Ophthalmic
Public Knowledge, Attitude, and Perception Toward Conventional and Novel Ocular Treatment in Malaysia

Abdullah SN, Mohmad Sabere AS

J Pharm Bioallied Sci, 2020 12 21;13(1):143-147.
PMID: 34084061 DOI: 10.4103/jpbs.JPBS_463_20

One of the major concerns in any pharmacological treatment is the patients' adherence to medication. However, different types of ocular dosage forms might result in different response and compliance from the patients. This study investigated and compared public willingness on different types of dosage forms available for ocular treatment. The study also evaluated their willingness on new approach for the treatment based on their knowledge, attitude, and perception. This study was conducted between October and December 2017 through a set of questionnaires applied to 90 respondents between the age of 18 and 60 years who lived in Muar and Kuantan, Malaysia. The results were analyzed using SPSS software version 22.0 including inferential and descriptive statistics. There was no significant difference in the knowledge level between all age groups towards different types of dosage forms available; eye drops (P = 0.09), eye ointment (P = 0.252), medicated contact lens (P = 0.05), ocular mini-tablets (P = 0.06), and ocular inserts (P = 0.075). There is a variation of results among the public towards different types of dosage forms with their willingness to try conventional and novel approach. Eye drops show the highest willingness followed by eye ointment (less willingness). However, most of them showed no willingness towards medicated contact lens, ocular mini-tablets, and ocular insert. This research hopes to provide an overview on the development process of new formulation and dosage forms based on the patients' willingness level in an attempt to increase patient compliance.

Matched MeSH terms: Administration, Ophthalmic
Intraocular pressure lowering effect and structure-activity relationship of imidazo[1,2-a]benzimidazole and pyrimido[1,2-a]benzimidazole compounds in ocular normotensive rats: Insight on possible link with hypotensive activity

Marcus AJ, Iezhitsa I, Agarwal R, Vassiliev P, Spasov A, Zhukovskaya O, et al.

Eur J Pharm Sci, 2018 Mar 01;114:245-254.
PMID: 29274441 DOI: 10.1016/j.ejps.2017.12.015

In an effort to find new ocular hypotensive drug candidates, a total of 27 condensed benzimidazoles based compounds were screened. This study was done in normotensive rats and rebound tonometry was used to estimate IOP. All compounds were topically applied as a single drop, unilaterally, at 3 different concentrations (0.1%, 0.2% and 0.4%). The contralateral eye was instilled with vehicle and served as control. The IOP reduction was measured up to 6h. It was observed that with a single topical instillation, compounds RU 551, RU 555, RU839 (pyrimido[1,2-a]benzimidazole derivatives), and RU 615 (imidazo[1,2-a]benzimidazole derivative) showed significant IOP lowering activities in ocular normotensive rats. All other compounds showed none, weak and inconsistent IOP lowering effect. The relationship between ability of IOP lowering and hypotensive activities was studied. According to the pharmacophore analysis, the class of pyrimido[1,2-a]benzimidazole is more promising than the class of imidazo[1,2-a]benzimidazole as a source of compounds with high IOP lowering activity. Pharmacophore analysis also showed that the critical features of high IOP lowering activity are methoxyphenyl and [phenyl]alkyl fragments, and non-conjugated six-membered heterocyclic ring.

Matched MeSH terms: Administration, Ophthalmic
Punctal plug: a medical device to treat dry eye syndrome and for sustained drug delivery to the eye

Yellepeddi VK, Sheshala R, McMillan H, Gujral C, Jones D, Raghu Raj Singh T

Drug Discov Today, 2015 Jul;20(7):884-9.
PMID: 25668579 DOI: 10.1016/j.drudis.2015.01.013

Punctal plugs (PPs) are miniature medical implants that were initially developed for the treatment of dry eyes. Since their introduction in 1975, many PPs made from different materials and designs have been developed. PPs, albeit generally successful, suffer from drawbacks such as epiphora and suppurative canaliculitis. To overcome these issues intelligent designs of PPs were proposed (e.g. SmartPLUG™ and Form Fit™). PPs are also gaining interest among pharmaceutical scientists for sustaining drug delivery to the eye. This review aims to provide an overview of PPs for dry eye treatment and drug delivery to treat a range of ocular diseases. It also discusses current challenges in using PPs for ocular diseases.

Matched MeSH terms: Administration, Ophthalmic
Recent Updates on Novel Approaches in Insulin Drug Delivery: A Review of Challenges and Pharmaceutical Implications

Pandey M, Choudhury H, Yi CX, Mun CW, Phing GK, Rou GX, et al.

Curr Drug Targets, 2018;19(15):1782-1800.
PMID: 29792143 DOI: 10.2174/1389450119666180523092100

Diabetes mellitus, a metabolic disorder of glucose metabolism, is mainly associated with insulin resistance to the body cells, or impaired production of insulin by the pancreatic β-cells. Insulin is mainly required to regulate glucose metabolism in type 1 diabetes mellitus patients; however, many patients with type 2 diabetes mellitus also require insulin, especially when their condition cannot be controlled solely by oral hypoglycemic agents. Hence, major research is ongoing attempting to improve the delivery of insulin in order to make it more convenient to patients who experience side effects from the conventional treatment procedure or non-adherence to insulin regimen due to multiple comorbid conditions. Conventionally, insulin is administered via subcutaneous route which is also one of the sole reasons of patient's non-compliance due to the invasiveness of this method. Several attempts have been done to improve patient compliance, reduce side effects, improve delivery adherence, and to enhance the pharmaceutical performance of the insulin therapy. Despite facing substantial challenges in developing efficient delivery systems for insulin, vast research studies have been carried out for the development of smart delivery systems to deliver insulin via ocular, buccal, pulmonary, oral, transdermal, as well as rectal routes. Therefore, the present review was aimed to overview the challenges encountered with the current insulin delivery systems and to summarize recent advancements in technology of various novel insulin delivery systems being discovered and introduced in the current market.

Matched MeSH terms: Administration, Ophthalmic
Prostaglandin F2-Alpha Eye Drops (Bimatoprost) in Graves' Orbitopathy: A Randomized Controlled Double-Masked Crossover Trial (BIMA Trial)

Draman MS, Morris DS, Evans S, Haridas A, Pell J, Greenwood R, et al.

Thyroid, 2019 04;29(4):563-572.
PMID: 30880626 DOI: 10.1089/thy.2018.0506

BACKGROUND: Previous in vitro experiments have demonstrated that prostaglandin F2-alpha (PF2α) reduced proliferation and adipogenesis in a murine cell line and human orbital fibroblasts derived from subjects with inactive Graves' orbitopathy (GO). The objective of this study was to determine if the PGF2α analogue bimatoprost is effective at reducing proptosis in this population.
METHODS: A randomized controlled double-masked crossover trial was conducted in a single tertiary care academic medical center. Patients with long-standing, inactive GO but persistent proptosis (>20 mm in at least one eye) were recruited. Allowing for a 15% dropout rate, 31 patients (26 females) were randomized in order to identify a treatment effect of 2.0 mm (p = 0.05; power 0.88). Following informed consent, participants were randomized to receive bimatoprost or placebo for three months, after which they underwent a two-month washout before switching to the opposite treatment. The primary outcome was the change in exophthalmometry readings over the two three-month treatment periods.
RESULTS: The mean exophthalmometer at baseline was 23.6 mm (range 20.0-30.5 mm), and the mean age of the patients was 55 years (range 28-74 years). The median duration of GO was 7.6 years (interquartile range 3.6-12.3 years). The majority were still suffering from diplopia (61.3%) with bilateral involvement (61.3%). Using multi-level modeling adjusted for baseline, period, and carry-over, bimatoprost resulted in a -0.17 mm (reduction) exophthalmometry change ([confidence interval -0.67 to +0.32]; p = 0.490). There was a mean change in intraocular pressure of -2.7 mmHg ([confidence interval -4.0 to -1.4]; p = 0.0070). One patient showed periorbital fat atrophy on treatment, which resolved on stopping treatment. Independent analysis of proptosis by photographic images (all subjects) and subgroup analysis on monocular disease (n = 12) did not show any apparent benefit.
CONCLUSIONS: In inactive GO, bimatoprost treatment over a three-month period does not result in an improvement in proptosis.

Matched MeSH terms: Administration, Ophthalmic
IOP lowering effect of topical trans-resveratrol involves adenosine receptors and TGF-β2 signaling pathways

Razali N, Agarwal R, Agarwal P, Froemming GRA, Tripathy M, Ismail NM

Eur J Pharmacol, 2018 Nov 05;838:1-10.
PMID: 30171854 DOI: 10.1016/j.ejphar.2018.08.035

Trans-resveratrol was earlier shown to lower intraocular pressure (IOP) in rats; however, its mechanisms of action remain unclear. It has been shown to modulate adenosine receptor (AR) and TGF-β2 signaling, both of which play a role in regulating IOP. Hence, we investigated effects of trans-resveratrol on AR and TGF-β2 signaling. Steroid-induced ocular hypertensive (SIOH) rats were pretreated with A1AR, phospholipase C (PLC) and ERK1/2 inhibitors and were subsequently treated with single drop of trans-resveratrol. Metalloproteinases (MMP)-2 and -9 were measured in aqueous humor (AH). In another set of experiments, effect of trans-resveratrol on AH level of tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA) was determined after single and multiple drop administration in SIOH rats. Effect of trans-resveratrol on ARs expression, PLC and pERK1/2 activation and MMPs, tPA and uPA secretion was determined using human trabecular meshwork cells (HTMC). Further, effect of trans-resveratrol on TGF-β2 receptors, SMAD signaling molecules and uPA and tPA expression by HTMC was determined in the presence and absence of TGF-β2. Pretreatment with A1AR, PLC and ERK1/2 inhibitors antagonized the IOP lowering effect of trans-resveratrol and caused significant reduction in the AH level of MMP-2 in SIOH rats. Trans-resveratrol increased A1AR and A2AAR expression, cellular PLC, pERK1/2 levels and MMP-2, tPA and uPA secretion by HTMC. Additionally, it produced TGFβRI downregulation and SMAD 7 upregulation. In conclusion, IOP lowering effect of trans-resveratrol involves upregulation of A1AR expression, PLC and ERK1/2 activation and increased MMP-2 secretion. It downregulates TGFβRI and upregulates SMAD7 hence, inhibits TGF-β2 signaling.

Matched MeSH terms: Administration, Ophthalmic