English oral delivery of drug was the commonly used modality because of patient compliance and ease of administration. After oral administration of any drug, its bioavailability is affected by its residence time in stomach. Recently, gastroretentive drug delivery systems (GRDDS) have gained wide acceptance for drugs with a narrow absorption window, decreased stability at high alkaline pH, and increased solubility at low pH. This approach develops a drug delivery system, which gets retained within gastric fluid, thereby releasing its active principles in the stomach. Some methods used to achieve gastric retention of drugs include the use of effervescence agents, mucoadhesive polymers, magnetic material, bouncy enhancing excipient, and techniques that form plug-like devices that resist gastric emptying. This review provides a concise account of various attributes of recently developed approaches for GRDDS.
Keywords: Bioavailability, bio/mucoadhesive system, therapeutic window, gastric emptyingOral administration is popular despite continuous improvement in drug delivery approaches owing to patient comfort and ease of administration. Controlled release drug delivery systems are designed for oral administration. These drug delivery systems release the medication in a predetermined, predictable, and controlled way. They are not suitable for drugs with low bioavailability due to stability or absorption issues. 1 These problems can get better through modern approaches, which are designed to increase the residence of such drugs in the stomach for an extended time. Such drug delivery systems are called gastroretentive drug delivery systems (GRDDS). GRDDS are suitable for those drugs, which are absorbed from the stomach (e.g. albuterol), 2 labile at alkaline pH (e.g. ranitidine and metformin), 3 poorly soluble at alkaline pH (e.g. furosemide and diazepam), 4 and having a narrow window of absorption (e.g. riboflavin and levodopa). 5
Some of the common advantages associated with use of GRDDS include improved patient compliance by reducing the frequency of dosing; improved therapeutic efficacy of drugs with a short half-life; site-specific delivery of medications; sustained and controlled release of drugs in the stomach; enhanced residence time of drugs at the absorption site; improved bioavailability from the gastrointestinal tract; avoiding dose dumping of medicines. 6
To develop GRDDS, different materials like ion-exchange resins, mucoadhesives, high-density materials, raft forming substances, magnetic substances, and super porous hydrogels are used. 7,8
This review provides a concise account of various attributes of recently developed approaches for GRDDS.
Knowledge about the anatomy and physiology of the stomach is essential for the successful formulation of gastroretentive dosage forms. Anatomically, the stomach is divided into three areas: the proximal portion toward the esophagus is fundus, followed by the body, which serves as a storage site for engulfed food, and the antrum, last part that connects the body to the small intestine. Antrum helps in churning action and in gastric emptying. 9 In fasting state, a sequence of contractions occurs cyclically through the stomach and intestine every 120-180 min, called the migrating myoelectric cycle. It is further divided into four phases. The pattern of contraction changes in a fed state is termed as the digestive motility pattern. 10 This pattern comprises phase 1- (basal phase); phase 2- (preburst phase); phase 3- (burst phase); and phase 4. 11 Figure 1 depicts the motility pattern in the gastrointestinal tract.
Motility pattern in gastrointestinal tract
