SWAPNA VELIVELA*, Dr. K. ABBULU, Dr. D.VARUN Acyclovir, Gelucire 43/01, Gelucire 50/02, Compritol ATO 888, Geleol Pellets 1350-1360 Volume 4, Issue 6 November - December 2013 The purpose of this investigation was to formulate hydrodynamically balanced gastric retentive drug delivery system of Acyclovir. Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). It has an elimination half life of about 2.5-3.3 hours. Non-effervescent formulations of Acyclovir were prepared with novel lipoid carriers like Gelucire 43/01, Gelucire 50/02, Compritol ATO 888, Geleol pellets by using different granulation techniques in the ratios of 1:1, 1:1.25 and 1:1.5 were compared to effervescent formulations comprising HPMC K4M, HPMC K15M, HPMC K100M. All the formulations were evaluated for Micromeritic properties, buoyancy parameters and in vitro drug release studies were carried out for 12 hours. The in vitro release data obtained was fitted to various linear and regression kinetic models to assess the release profile of the drug. Based on results obtained from the preliminary formulations, optimized formulations are selected for further studies. Short-term stability studies were done for optimized formulations. The data obtained in this study suggests that the multiunit floating formulations of Acyclovir can be successfully designed to give controlled drug delivery and improved oral bioavailability.