Advanced polymers and recent advancements on gastroretentive drug delivery system; a comprehensive review

Oral route of drug administration is typically the initial option for drug administration because it is both practical and affordable. However, major drawback of this route includes the release of drug at a specified place thus reduces the bioavailability. This could be overcome by utilising the gastroretentive drug delivery system (GRRDS). Prolonged stomach retention improves bioavailability and increases solubility for medicines that are unable to dissolve in high pH environments. Many recent advancements in the floating, bio adhesive, magnetic, expandable, raft forming and ion exchange systems have been made that had led towards advanced form of drug delivery. From the past few years, floating drug delivery system has been most commonly utilised for the delivery of drug in a delayed manner. Various polymers have been utilised for manufacturing of these systems, including alginates, chitosan, pectin, carrageenan's, xanthan gum, hydroxypropyl cellulose, carbomer, polyethylene oxide and sodium carboxy methyl cellulose. Chitosan, pectin and xanthan gum have been found to be most commonly used polymers in the manufacturing of drug inclusion complex for gastroretentive drug delivery. This study aimed to define various types and advanced polymers as well as also highlights recent advances and future perspectives of gastroretentive drug delivery system.

Development of Gabapentin Expandable Gastroretentive Controlled Drug Delivery System

Expandable drug delivery systems are one of many gastroretentive delivery systems which have emerged during the last few years. Expandable systems are usually folded in a capsule and expand to dimensions greater than the pyloric sphincter upon contact with gastric fluid. This prevents them from being evacuated by gastric emptying. The main objective of developing such systems is to increase the residence time of a specific drug in stomach; controlling its release, increasing its bioavailability and decreasing its side effects and dosing frequency. An expandable gastroretentive drug delivery system containing Gabapentin was developed using experimental design (D-optimal reduced quadratic design). This system was able to unfold at stomach pH in less than 15 minutes and obtain a controlled release of 78.1 ± 4.7% in 6 hours following zero-order release kinetic model. It is rigid in stomach and its rigidity decreases at intestinal pH. FTIR analysis indicated the occurrence of hydrogen bonding in Gabapentin when present in the developed system, which might be responsible for the drug’s controlled release. XRD analysis indicated that Gabapentin physical properties changed from crystalline in the typical state to amorphous in the developed system.

Improved bioavailability of Azelnidipine gastro retentive tablets-optimization and in-vivo assessment

Azelnidipine, dihydropyridine based calcium channel blocker has been used for treating ischemic heart disease and cardiac remodeling after myocardial infarction but it is having a low bioavailability due to its poor solubility. The present study is to investigate the formulation and evaluation of floating tablets of Azelnidipine for controlled release and to increase bioavailability by increasing the gastrointestinal transit time and mucoadhesion of drug. The gastro retentive tablets were prepared by direct compression method using different concentrations of combination of Polyoxyethylene oxide WSR 303 as hydrophilic polymer and Potassium bicarbonate as gas generating agent. Main effects of the formulation variables were evaluated quantitatively using design approach showing that both independent variables have significant effects on floating lag time, % drug release at 1 h (D1 h) and time required to release 90% of the drug (t90). The statistically optimized formulation (F3) released 95.11 ± 1.43% drug for 12 h followed K-Peppas drug release kinetics indicating release of drug by diffusion and erosion mechanism. Evaluation of the optimized formulation in vivo in human volunteers showed that the GFT was buoyant in gastric fluid and that its gastric residence time was enhanced. Pharmacokinetics studies carried out revealed significant (P < 0.05) equivalent Cmax, longer Tmax and higher AUC values for the optimized formula compared to the marketed oral product. From the results obtained it can be concluded that Azelnidipine Gastro retentive tablets with enhanced bioavailability and better release pattern is suitable for more effective treatment compared to marketed conventional tablets.

Overview on gastroretentive drug delivery systems for improving drug bioavailability

In recent decades, many efforts have been made in order to improve drug bioavailability after oral administration. Gastroretentive drug delivery systems are a good example; they emerged to enhance the bioavailability and effectiveness of drugs with a narrow absorption window in the upper gastrointestinal tract and/or to promote local activity in the stomach and duodenum. Several strategies are used to increase the gastric residence time, namely bioadhesive or mucoadhesive systems, expandable systems, high-density systems, floating systems, superporous hydrogels and magnetic systems. The present review highlights some of the drugs that can benefit from gastroretentive strategies, such as the factors that influence gastric retention time and the mechanism of action of gastroretentive systems, as well as their classification into single and multiple unit systems.