Development and Evaluation of Gastroretentive Floating Tablets of an Antihypertensive Drug Using Hydrogenated Cottonseed Oil

The aim of the present work was to develop a gastroretentive floating tablet of Atenolol and investigate the effects of both hydrophilic and hydrophobic retardant on in vitro release. Atenolol is an antihypertensive drug with an oral bioavailability of only 50% because of its poor absorption from lower gastrointestinal tract. The floating tablets of Atenolol were prepared to increase the gastric retention, to extend the drug release, and to improve the bioavailability of the drug. The floating tablets were formulated using hydrophilic polymers as Hydroxy propyl methyl cellulose (HPMC K4M and HPMC K15M), hydrophobic retardant as a hydrogenated cottonseed oil (HCSO), and sodium bicarbonate as a gas generating agent to reduce floating lag time. The formulated tablets were evaluated for the quality control tests such as weight variation, hardness, friability, swelling index, floating lag time, and total floating time. The in vitro release study of the tablets was performed in 0.1？N HCl as a dissolution media. The results of the present study clearly indicates the promising potential of Atenolol floating system as an alternative to the conventional dosage and other sustained release formulations. The study also revealed the effectiveness of HCSO as retardant in combination with HPMC. 1. Introduction The oral bioavailability of many drugs is limited by their unfavourable physicochemical characteristics or absorption in well-defined part of the gastrointestinal tract (GIT) referred as “absorption window” [1]. Prolonged gastric retention improves bioavailability, reduces drug waste, and improves the solubility for drugs that are less soluble in a high pH environment [2]. Various approaches have been investigated to increase the retention of oral dosage form in the stomach, including floating systems, swelling and expanding systems, bioadhesive systems, modified shape systems, high density systems, and other delayed gastric emptying devices [1]. Atenolol is a beta (1)-adrenergic antagonist or more commonly known as a beta-blocker used in the treatment of hypertension and angina pectoris. Chemical name of Atenolol is 4-[2-hydroxy-3-[(1-methyl ethyl)amino]propoxy]benzene acetamide. Molecular structure of Atenolol is as shown Figure 1. Figure 1: Structure of Atenolol. Atenolol undergoes little or no hepatic first pass metabolism and its elimination half-life is 6 to 7 hours. The present modes of administration of Atenolol are oral and Parenteral. It is incompletely absorbed from the gastrointestinal tract and has an oral bioavailability of only 50%, while the