Sustained release

Gastroretentive drug delivery systems (GRDDS) have emerged as an advanced approach to overcome the limitations of conventional oral dosage forms by prolonging gastric residence time and improving drug bioavailability. The objective of these systems is to remain buoyant in gastric fluid for extended periods, allowing controlled release of drugs and enhanced absorption of medications with limited absorption windows. Floating tablets achieve buoyancy using low-density excipients, such as gas-generating substances like sodium bicarbonate, or swellable polymers like hydroxypropyl methylcellulose (HPMC). Formulation strategies generally employ polymeric matrices, effervescent components, or coating technologies to regulate release kinetics and enhance stability. Evaluation parameters, such as floating lag time, total floating duration, and in vitro and in vivo correlation, are essential for assessing system performance. GRDDS can improve the therapeutic efficacy of medicines used in gastrointestinal disorders and those requiring localized gastric delivery. Despite significant advancements, variability in gastric motility and physiological factors limit the reproducibility and scalability of formulations. This review consolidates current progress and identifies future directions for optimized gastroretentive floating tablet technology.

The aim of present work was to design and evaluate sustained release matrix tablets of antihyperlipidemic drug. In the present investigation, polymers used in different combinations such as Eudragit RL100 and HPMC E5 in the ratio of 1:1, 1:2, 1:3 and vice versa with PVP K25 using direct compression technique were prepared. The tablets were evaluated for physical parameters like thickness, hardness, friability, weight variation, and in vitro release studies. The FTIR study indicated that the drug is stable in formulation. The maximum drug release was found to be 94.41% over a period for 12 hours for F4 batch, thus concluded that as the concentration of Eudragit RL100 is increased the drug release decreased. The drug release mechanism followed non-fickian transport from both polymer matrices. All the formulations were stored at 250C/60% RH and 450C/75% RH for 3 months. It showed that all the formulations were physically and chemically stable.

The objective of the study was preparation of sustained release matrix tablets by hot melt extrusion (HME) and process optimization for continuous manufacturing. Furthermore, HME tablets were evaluated with respect to in vitro release rate, erosion behavior and water uptake study. Hydroxypropylcellulose (HPC) was used as release retarding polymer. The drug chosen for study was first line anti tuberculosis drug rifampicin. 50 % drug loaded HME tablets were prepared. The HME tablets were characterized by DSC, FTIR and SEM. No chemical interaction was found between drug and polymer as per DSC and FTIR. Dispersion of drug particles and internal micro pores was observed by SEM. In vitro release study revealed 50% drug loaded HPC matrix tablets gave sustained release of 101.41±1.02% at the end of 24 h. Release rate of rifampicin from HME tablets was found to be dependent on the concentration of polymers and plasticizer. The release rate from the edges and circumference of tablets suggested the hydration of the tablets from the circumference was more significant than at edges of the tablets. Drug release from HME matrix tablets was found to follow Super case-II transport mechanism. HME tablets were stable for six months as per ICH guideline.

The purpose of the study was to formulate floating alginate beads of Nevirapine (NVP), an Anti-HIV agent. Inspite of long half life (45 hrs) a Nevirapine controlled release once daily formulation could be used to maintain optimum peak plasma concentration for effective viral suppression. The floating bead formulations were prepared by dispersing Nevirapine together with Sodium bicarbonate in a mixture of sodium alginate and Hydroxypropyl methylcellulose solution and sunflower oil and then dripping the dispersion into an acidified solution of calcium chloride. Calcium alginate beads were formed, as the alginate underwent Emulsion gelation by calcium ions, and carbon dioxide developed from the reaction of carbonate salts with acid. The obtained beads were able to float due to CO2 -gas formation and the gas entrapment by the polymeric membrane. The prepared beads were evaluated for percent drug loading, drug entrapment efficiency, morphology, surface topography, buoyancy, in-vitro release, and release kinetics. The beads containing higher amounts of calcium carbonate demonstrated an instantaneous, complete, and excellent floating ability over a period of 24 hours. And this floating beads are compared and evaluated with Nevirapine floaing gel, Good floating properties and sustained drug release were achieved. Finally, these floating beads seemed to be a promising gastro retentive drug delivery system.

The oral route of administration is considered as the most widely accepted route because of its convenience of self administration, compactness and easy manufacturing, in which the sustain release drug delivery replaces the conventional administration of drug by delivery system. Recently, greater emphasis has been placed on controlling the rate and or site of drug release from oral formulations for the purposes of improving patient compliance and treatment efficacy, solving problems concerning targeting of a drug to a specific organ or a tissue and controlling the rate of a drug delivery to the target site. Matrix system are favored because of they are easy to formulate, and showing better patient compliance, effective etc, than ancient drug delivery, which showing many drawbacks like repeated administration, fluctuation in drug plasma level etc.; developing oral sustained release matrix tablet with constant release rate has always being beneficial to the pharmaceutical technologist. Matrix type drug delivery systems are an interesting and promising way for developing an oral controlled release system, which will maximize the pharmacological benefits and minimize the potential side effects. The matrix tablet releases the drug in continuous manner like diffusion and dissolution controlled way. Hydrophilic polymers with high gelling capacity are of particular interest in the field of matrix tablet. Key words: Sustained release, Oral formulations, Hydrophilic polymers, Matrix tablet.

  The objective of this study was to formulate and evaluate gastroretentive effervescent floating  matrix  tablet of two anti-asthmatic drugs, Salbutamol sulphate and Theophylline which are often indicated for the management of asthma, their frequent dosing may reduce compliance, thus making a prolonged release formulation necessary. Tablets were prepared by wet granulation method using Hydroxy propyl methylcellulose (HPMC) as a release retardant agent and sodium bicarbonate and Citric acid as a gas-generating agents. The prepared granules showed satisfactory flow properties and compressibility. Formulations were evaluated for in vitro drug release profile and swelling characteristics. The similarity factor and dissolution kinetics were used as parameters for selection of the best batch. The result of formulation C7 batch showed the best result and was found to extend the release of Salbutamol Sulphate and Theophylline upto 12 hr. and was found to be comparable with marketed sustained released tablet Theoasthalin SR (Cipla). The in- vitro drug release followed Korsemeyer-Peppas kinetics and the drug release mechanism was found to be of anomalous type i.e, swelling and diffusion.