A Review Article On: Gastro-Retentive Drug Delivery System (GRDDS)

A new method of medication administration is represented by gastro-retentive drug delivery systems (GRDDS). Increasing a drug's duration of residency in the stomach is their main goal in order to guarantee site-specific release in the upper gastrointestinal tract for both local and systemic effects. (3) all the delivery methods to the systemic circulation, oral administration is the most practical and favoured. (1) Regular use of these drugs is necessary for their effectiveness. Additionally, because to the short gastric emptying time of 2.7±1.5 hours (h) and the intestinal transit time of 3.1±0.4 hours, oral, sustained release systems are not appropriate for medicines with low absorption fencing in the upper region of the GIT. (5) The inability of sustained release dosage forms to extend the dosage form's residence duration in the stomach and proximal section of the small intestine is a common issue. Therefore, creating formulations with sustained release that stay at the absorption site for a long time would be advantageous. One potential strategy for attaining the desired and delayed medication delivery profile in the GIT is to regulate the formulation's gastric retention time (GRT). (6) Fast gastrointestinal transit may hinder the full release of a drug in the absorption area, decreasing the effectiveness of the given dose, as most drugs are absorbed in the stomach or the initial section of the small intestine. Floating drug delivery systems present various advantages for medications with low bioavailability due to the limited absorption window in the upper region of the gastrointestinal tract. (9)

GRDDS is utilized for medications that deteriorate in the colonic area. It is also advantageous for: 

– Decreasing the required dosage of the drug. 

– Keeping a consistent concentration of the drug in the bloodstream. 

– Minimizing variations in the therapeutic concentration of the drug. (13)

Dosage forms that stay in the stomach longer than traditional dosage forms benefit greatly from the capacity to extend and regulate the emptying time because the process of gastric emptying is incredibly varied. Constricting the dose form to the appropriate region of the gastrointestinal tract is one of these challenges. (10)

Physiology of Stomach:

The stomach can be separated anatomically into three areas. Body, Antrum, and Fundus (pylorus) The smallest part made of fundus is the main centre for mixing motions and serves as a pump for stomach emptying by driving the movement of the fundus and body, which serves as a reservoir for undigested materials activities. (2) The former, which passes through the stomach and intestine every two to three hours, is stronger while fasting and serves the main purpose of clearing the upper GI tract of everything that remains. This is arranged into cycles of activity and passiveness and is known as the inter digestive myloelectric activity cycle or migrating myloelectric cycle (MMC). (6) There are four phases in each cycle, which lasts 90 to 120 minutes. The amount of the phases is determined by the blood's level of the hormone motilin. The several stages are listed below.

Phase I (basal phase): 40–60 minutes during which there is no contraction;

Phase II (pre-burst phase): Intermittent contraction period (20–40 minutes),

Phase III (burst phase): It is characterised by compatible contractions at maximum frequency that move distally, also known as the housekeeping wave. These movements are powerful and occur for a short period. This wave removes undigested material from the stomach and transfers it to the small intestine (10-20 minutes).

Phase IV: It is the transition period between phases III and I (0-5 minutes). (6)