Mucoadhesive Microspheres as a Controlled Drug Delivery System for Gastroretention

Context: Drugs that are easily absorbed from the gastrointestinal tract (GIT) and have a short halflife are eliminated quickly from the blood circulation, require frequent dosing. To avoid this, the oral controlled release (CR) formulations have been developed in an attempt to release the drug slowly into the GIT and maintain a constant drug concentration in the serum for longer period of time. Such oral drug delivery devices have a restriction due to a short gastric retention time (GRT), a physiological limitation. Therefore, devices which prolong gastric retention by retaining the CR system in the stomach for a longer time have been developed and explored over the past couple of years. Objectives: A mucoadhesive microsphere is one potential strategy for prolonging GRT. The present review will give a comprehensive study of research done on the formulation of microspheres using mucoadhesive polymers, the in vitro evaluation techniques employed with a special discussion on recent in vivo techniques used. Results and Conclusion: Mucoadhesive microspheres interact with mucous of GIT and are considered to be localized or trapped at the adhesive site by retaining a dosage form at the site of action, or systemic delivery by retaining a formulation in intimate contact with the absorption site which may result in prolonged gastric residence time as well as improvement in intimacy of contact with underlying absorptive membrane to achieve better therapeutic performance of drugs. residence time of the drug 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.[1,2] Therefore, control of placement of a drug delivery system in a specific region of the GI tract offers advantages for a variety of important drugs characterized by a narrow absorption window in the GIT or drugs with a stability problem.[3] These considerations have led to the development of a unique oral controlled release dosage form with gastroretentive properties. There are numerous approaches which have been adopted to develop gastroretentive dosage form to prolong the gastric residence time. Gastroretentive dosage form may be broadly classified into mucoadhesive systems, floating systems, high density systems, expendable systems, super porous hydrogel systems and magnetic systems.[4-7] They enable oral therapy of drugs with narrow absorption window in upper part of GIT, having short half life (t1/2 2-8 h) or drugs with poor stability. Furthermore the gastroretentive system can act locally within the stomach and prolong the intimate contact with the absorbing membrane thus increasing its efficacy. The detailed literature on classification of gastroretentive systems has been well reviewed elsewhere.[8-10] The most common approach was gastroretention based on floating system. The disadvantage of floating devices administered in a single-unit form such as hydrodynamically balanced systems (HBS) are unreliable in prolonging the GRT owing Access this article online Website: www.sysrevpharm.org Quick Response Code: DOI: 10.4103/0975-8453.107130