INDIAN DRUGS 54 (04) ApRIl 2017 47 GASTRORETENTIVE MICROBALLOONS OF RIBOFLAVIN: FORMULATION AND EVALUATION Penjuri S. C. B.*, Nagaraju R., Shaik S., Damineni S. and Poreddy S. R. (Received 09 July 2016) (Accepted 13 March 2017) ABSTRACT Gastroretentive dosage forms are useful to extend release of drugs having a narrow window of absorption in the upper intestine and for drugs degraded by higher pH or for drugs with local action in the proximal part of the GI tract. In the present study, an attempt was made to prepare microballoons of riboflavin by emulsion solvent diffusion method by using HpMC and ethylcellulose in order to extend the drug release in the upper GIT, which may result in enhanced absorption and thereby improved bioavailability. The size and surface morphology of riboflavin microballoons were characterized by optical and scanning electron microscopy. FTIR and DSC studies revealed no drug excipient interaction. Average particle size of microballoons was found to be between 126.8±2.26 to 163.4±2.52 μm. Microballoons were found to be spherical in shape with smooth surface texture. percentage yield of the microballoons was satisfactory. In vitro buoyancy of the optimized riboflavin microballoons was found to be 96.24±0.08%, indicating good floating in stomach. Cumulative amount of drug release from microballoons at the end of 12 hr was 99.78±2.78 % and followed Highuchi diffusion kinetics and super case II transport. Keywords: Gastroretentive system, hollow microballoons, riboflavin, HpMC K4M, ethyl cellulose, emulsion solvent diffusion method. INTRODUCTION Drugs that are easily absorbed from the gastrointestinal tract and have a short half-life are eliminated quickly from the blood circulation and require frequent dosing. Some of the drugs are characterized by a narrow absorption window (NAW) in the upper part of the GIT i.e. the stomach and small intestine 1 . This is because the proximal part of the intestine exhibits extended absorption properties. Despite this, the extent of absorption at these sites is limited because the passage through this region is rapid. After a short period of time, the drug delivery system leaves the upper GIT and releases the drug in the non-absorbing distal segments of the GIT. As a consequence, their oral bioavailability can be affected 2 . The gastro-intestinal residence time (GRT) determines the time period available for drug release from its dosage form within the gastrointestinal tract 3 . Gastroretentive drug delivery systems (GRDDS) may provide increased *For Correspondence: Department of Pharmaceutics, MNR College of Pharmacy, Sangareddy - 502 294, Telangana, India E-mail: penjurisubhash@gmail.com bioavailability for drugs that are absorbed in the upper region of the GIT. Approaches to increase the GRT include bioadhesive drug delivery systems, which adhere to mucosal surfaces 4 , swellable delivery systems, which swell and retard the passage through the pylorus 5 and density-controlled delivery systems, which either float or sink in gastric fluids 6-8 . Floating drug delivery system is used particularly for drugs which act locally in the stomach, are absorbed in stomach, have poor solubility in alkaline pH, have a narrow window of absorption or are unstable in the intestinal or colonic environment 3 . Riboflavin (Vitamin B2) demonstrates absorption mainly in the proximal segment of the small intestine, it is a compound classified as a “NAW” drug 1 . It is used for the treatment of ariboflavinosis associated with weakness, throat soreness/swelling, tongue swelling (glossitis), angular stomatitis/cheilosis (skin or sores at the corners of the mouth), dermatitis (skin irritation) and anemia. previous approaches for increasing the bioavailability of riboflavin by floating microspheres 2 , floating microballoons 1 , floating films 9 , collagen sponges 10 , pills 11 and micro pellets 12 have been reported. MATERIALS AND METHODS Riboflavin was a gift sample from Dr. Reddy’s labs limited, Hyderabad. Ethyl Cellulose and HpMC were purchased from Qualigens Fine Chemicals, New Delhi. All other ingredients used were of analytical grade.