An overview on various approaches to Gastroretentive dosage forms

Over the past four decades, gastro retentive dosage forms have recently become a leading methodology in the field of site-specific orally administered controlled release drug delivery system.. Gastroretentive dosage forms have the potential to improve local therapy with an increase of short gastric residence time and unpredictable gastric emptying time and decrease the variation in bioavailability which is unobserved, in other commercially available preparations. With the advent to current scientific and patented literature, this review have covered in detail the recent developments of FDDS including the physiological and formulation variables affecting gastric retention, classification, approaches to design single and multiple unit floating systems, formulation aspects and invitro and invivo studies to evaluate the performance. *Corresponding author, Mailing address: Sarojini Sarangapani Assistant Professor, No.2/IA.Dowlath nagar, Semmandalam post, Cuddalore -607 001. E-mail: [email protected] Ph: 9940565759 Article History:-----------------------Date of Submission: 06-11-2011 Date of Acceptance: 29-11-2011 Conflict of Interest: NIL Source of Support: NONE R e v i e w P a p e r C o v e r e d i n I n d e x C o p e r n i c u s w i t h I C V a l u e 4 .6 8 f o r 2 0 1 0 Int. J. Drug Dev. & Res., Jan-March 2012, 4 (1): 01-13 Covered in Scopus & Embase, Elsevier 1 patient compliance. Approximately 50% of the drug delivery systems available in the market are oral drug delivery system [1]. Although tremendous advances seen in de novo design of an oral controlled drug delivery system during last two decades, it has limited success in case of drugs with a poor absorption window throughout the GIT (Gastro Intestinal Tract). This approach is bedilled with several physiological difficulties such as inability to restrain and locate the controlled drug delivery system within the desired region of the gastrointestinal tract (GIT) due to variable gastric emptying and motility. Furthermore, the relatively brief gastric emptying time in humans which normally averages 2-3 h through the major absorption zone, i.e., stomach and upper part of the intestine can result in incomplete drug release from the drug delivery system leading to reduced efficacy of the administered dose [2]. To formulate a site-specific orally administered controlled release dosage form, it is desirable to achieve a prolonged gastric residence time by the drug delivery. Prolonged gastric retention improves bioavailability, increases the duration of drug release, reduces drug waste, and improves the drug solubility that are less soluble in a high pH environment [3]. Several gastro retentive drug delivery approaches being designed and developed, including: high density (sinking) systems that is retained in the bottom of the stomach [4], low density (floating) systems that causes buoyancy in gastric fluid [5, 6, 7], mucoadhesive systems that causes bioadhesion to stomach mucosa [8], unfoldable, extendible, or swellable systems which limits emptying of the dosage forms through the pyloric sphincter of stomach [9,10], superporous hydrogel systems[11], magnetic systems [12] etc. . BASIC GIT PHYSIOLOGY Anatomically the stomach is divided into three regions Fundus, Body and Antrum (pylorus) The proximal part made of fundus and body acts as a reservoir for undigested materials, where as the antrum is the main site for mixing motions and acts as a pump for gastric emptying by propelling actions [13,14]. Gastric emptying occurs in both the fasting and fed states. During the fasting state an interdigestive series of electrical events take place which cycle both through stomach and intestine every 2-3 hrs, which is called as interdigestive myloelectric cycle or migrating myloelectric cycle (MMC) which is further divided in to four phases. After the ingestion of a mixed meal, the pattern of contractions changes from fasted to that of fed state which is also termed as digestive motility pattern [15]. Structure of stomach Schematic representation of interdigestive motility R e v i e w P a p e r C o v e r e d i n I n d e x C o p e r n i c u s w i t h I C V a l u e 4 .6 8 f o r 2 0 1 0 S. Sarojini et al: An overview on various approaches to Gastroretentive dosage forms