sustained release.

The eye is one of the most delicate organs in our body. The eye is a complex organ characterized by its low permeability, short precorneal residence time, and small area for absorption, which pose significant barriers to drug delivery. Typically, less than 10% of a drug administered penetrates the eye. Traditional ocular delivery systems are also constrained, with significant drug loss due to tears and blinking, leading to blurred vision and untimed release events without sustained action, resulting in suboptimal outcomes in ocular therapy. To overcome such challenges, in situ ophthalmic gels have been developed. These gels' ability to transition from a liquid to a gel state allows for sustained drug release at the target site. In situ gel systems are in solution form before administration and then convert to a gel under physiological conditions (pH, temperature, or ionic concentration). This review discusses the anatomy and physiology of the eye, the challenges of ocular drug delivery, types of in situ gelling systems, mechanisms of gel formation, types of smart polymers, and methods for evaluating polymeric in situ gels.   

The current work deals with the formulation and development of sustained release tablets of Aceclofenac using natural polymers. Anacardium Occidentale (Cashew) gum and xanthan gum were used as a sustained release polymers. Literature survey has revealed that Anacardium Occidentale (Cashew) gum has been used as a pharmaceutical excipient, namely: as a binding agent in tablet formulations, emulsifying agent in emulsions, suspending agent in suspensions and mucoadhesive in mucoadhesive tablet. In this present study we tried to explore its drug release control properties. Aceclofenac drug was used as model drug and xanthan gum was used alone and in combination with cashew gum. Collected cashew gum was purified and checked for its purity by determination of microbial load. Different formulations were set by taking different concentrations of cashew gum, xanthan gum and combinations of both the gums. Tablets were prepared using wet (non-aqueous) granulation method. The flow properties of the granules were evaluated (angle of repose, bulk density, taped density, Car’s index, Hausner’s ratio) and the physical properties of the compressed tablets, namely dimensions, uniformity of weight, hardness, friability and dissolution rate were determined. All results obtained from these tests were found to be within permissible limit. The granules had good flow properties as evidenced by their Hausner’s ratio and Carr’s index values. From the overall result obtained and drug release profile we can conclude that cashew gum can be used as sustained release polymer in sustained release tablet.

Gum odina, a natural polymer of carbohydrate moiety, has already been shown its potential as pharmaceutical excipient as a binder in tablet dosage form and also as an emulsifying agent but very little data are available regarding the use of it as controlled release polymer. In the present study the objective was to investigate the potential use of gum odina as natural release retarding material in sustained release drug delivery system (matrix tablet) using tramadol hydrochloride as a model drug. Tablet containing tramadol hydrochloride was prepared using gum odina and further coated with Eudragit L 100 to prevent its release in stomach. The prepared tablets were evaluated for physical characterization and in-vitro drug release. The results of this study has proven the suitability of using gum odina as an alternative to existing natural polymer in the field of controlled delivery of drug with a significant effect on drug release and desired release rate of drug from tablets.

Drug release retarding polymers are the key performers in sustained release drug delivery system for which various natural, semi-synthetic and synthetic polymers have been investigated. The use of natural polymers over synthetic has gained importance due to their biodegradable, biocompatible, cost effectiveness and safety considerations. The present study deals with isolation of mucuna gum from the species of Mucuna flagillepes (Papillionaceae) and evaluating its suitability as a microencapsulating agent for delivery of propranolol hydrochloride. The gum was extracted from mucuna seeds by using 1% sodium-meta bisulphite as solvent followed by precipitation with acetone. The extracted gum was evaluated for physical characteristics like melting point, solubility, pH, total ash and micromeritic properties. Propranolol hydrochloride, a non selective beta-adrenergic receptor blocking agent was chosen as a model drug for formulation of microspheres with different drug: polymer [1:1-2.5] ratios by emulsification solvent evaporation method. The microspheres were evaluated for yield, particle size, drug loading efficiency and in-vitro drug release studies. The drug-polymer compatibility was confirmed by IR spectroscopy. The yield of formulations was found to be between 79 to 90.3% with the average particle size between 55.8 to 74.5µm.The drug encapsulation efficiency of microspheres was found to be in the range of 67.7 to 89.9%. The in-vitro drug release studies revealed that the polymer had positive effect on the drug retarding efficiency. The selected microspheres showed sustained and complete drug release up to 12 hours. Thus mucuna gum as a natural biodegradable polymer proved to be a suitable drug release encapsulate.