No abstract
Eye is the most sensitive organ of the body. Designing of ocular drug delivery system is the most challenging field for pharmaceutical scientists as less than 5% of administered drug enters the eye due to the complicated anatomical structure of the eye, small absorptive surface and low transparency of the cornea, lipophilicity of corneal epithelium, pre corneal loss (due to nasolacrimal drainage), bonding of the drug with proteins contained in tear fluid, blinking, low capacity of conjunctival sac, that restricts the entry of drug molecule at the site of action and ultimately leads to poor ocular therapy. To improve ophthalmic drug bioavailability, there are considerable efforts directed towards newer drug delivery systems for ophthalmic administration. These novel drug delivery systems offer manifold advantages over conventional systems as they increase the efficiency of drug delivery by improving the release profile and also reduce drug toxicity. A lot of research going on in this area proves the fact that in situ gelling systems can be beneficial in the ocular drug delivery. In situ gel forming systems are drug delivery systems that are in solution form before administration in the body but once administered, undergo in situ gelation, to form a gel triggered by external stimulus such as temperature, pH etc. This review is to Specify a brief summary about in situ gels, various approaches for in situ gelling systems, different types of polymers used in in situ gels, their mechanisms of gel formation and evaluation of polymeric in situ gel.Keywords: in situ gel, polymers, Temperature induced in situ gel system, pH induced in situ gel system, Ion activated systems.
The drugs having a narrow absorption window in the gastrointestinal tract (GIT) when administered by oral route are often limited by poor bioavailability due to incomplete drug release and short residence time at the site of absorption. Novel drug delivery systems in the form of gastroretentive systems such as floating systems, mucoadhesive, high-density, expandable have been developed as they provide controlled delivery of drugs with prolonged gastric residence time. Liquid orals are more prone to low bioavailability because they are eliminated quickly from the stomach since they are subjected to faster transit from the stomach/ duodenum. The problems of immediate release and short gastrointestinal residence of liquids are eliminated by formulating as oral in situ gels as they provide the best means to overcome these problems The in situ gel dosage form is a liquid before administration and after it comes in contact with gastric contents due to one or more mechanisms gets converted to gel which floats on gastric contents. This achieves increased residence as well as sustained release. This approach is useful for systemic as well as local effect of drugs administered. This review gives a brief idea about floating oral in-situ gel formation and research done by various scientists on a number of drugs and polymers. Keywords: Floating drug delivery, gastric retention time, In-situ gel.
Nanoemulsions are defined as isotropic, thermodynamically stable, transparent or translucent; dispersions of oil and water stabilized by surfactant molecules (forms an interfacial film) having the droplet size of 20-500nm. Ease of preparation and scale-up, stability and increased bioavailability are features of these formulations which have attracted the attention of researchers. Its basic principle lies in its ability to spontaneously generate fine o/w microemulsion under mild agitation following dilution with aqueous phases. These conditions mimic the digestive motility in the GIT necessary to provide the agitation required for In vivo self emulsification. Unlike emulsions, self-nanoemulsified drug delivery systems (SNEDDS) generates microemulsion with a narrow droplet size distribution of less than 50 nm due to which these systems have also been addressed as nanoemulsions. Nanoemulsions (NE) are lipidic nanoformulations with droplet diameter in nanometer range have established tremendous attention as drug delivery formulations for lipophilic drugs due to their capability to increase solubility, permeation across biological membranes as well as their therapeutic efficiency of lipid soluble drugs due to predictable size-distribution, high drug loading and stability under biological environment. However there is still relatively narrow insight regarding preparation, characterization and applications of nanoemulsions. This limitation unfolds the premise for current review article. In this review, we attempt to explore varying intricacies, methods of preparation, characteristics, and drug delivery applications of nanoemulsions to spike interest of those contemplating a foray in this field. Keywords: Nanoemulsions, Novel drug delivery system, increased bioavailability.
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