Formulation and Evaluation of Acyclovir Floating Matrix Tablets for Sustained Gastro-Retention

Abstract

Acyclovir is a commonly prescribed antiviral drug; however, its therapeutic effectiveness after oral administration is restricted by poor bioavailability and rapid gastric emptying. The present investigation focused on the development and assessment of gastro-retentive floating matrix tablets of acyclovir designed to prolong gastric residence time and provide sustained drug delivery. The formulations were prepared using hydrophilic release-retarding polymers, namely HPMC K100M and xanthan gum, along with sodium bicarbonate as an effervescent agent to impart buoyancy. Pre-compression evaluation of the powder mixtures demonstrated satisfactory micromeritic properties, indicating good flow and compressibility characteristics. Parameters such as Hausner’s ratio (1.024–1.306), Carr’s compressibility index (9.27–11.84%), and angle of repose (26.24°–26.83°) confirmed the suitability of the blends for direct compression. Post-compression analysis showed that all prepared tablets complied with official pharmacopeial limits for physical quality attributes, including uniformity of weight, tablet hardness (4.2–4.7 kg/cm²), friability below 0.3%, swelling behavior, and drug content ranging from 96.79% to 99.57%. Buoyancy testing demonstrated floating lag times between 4.3 and 5.1 minutes, while most formulations remained buoyant for more than 10 hours, indicating effective gastro-retentive performance. In vitro dissolution studies confirmed prolonged drug release over a period of 12 hours, with formulations containing higher concentrations of HPMC K100M exhibiting a slower and more controlled release pattern. Compatibility and stability investigations using FTIR and UV spectroscopy revealed no significant interaction between acyclovir and the selected excipients. Overall, the developed floating matrix tablets demonstrated effective gastro-retentive and sustained-release characteristics, suggesting their potential to improve the oral bioavailability of acyclovir and enhance patient adherence through reduced dosing frequency.

Keywords: Acyclovir, floating matrix tablets, gastro-retentive drug delivery, HPMC K100M, xanthan gum, sustained release.