A biphasic gastroretentive drug delivery system of acyclovir consisted of loading dose tablet
and floating multiple matrix tablets was prepared by direct compression process. The delivery system was
designed by hydroxy propyl methyl cellulose as retardant polymer with an effervescent component to get
the desired buoyant and sustained release characteristics. All formulations compile within the limits. The
FTIR studies did not show any evidence of an interaction between acyclovir and polymers. Dissolution
studies revealed biphasic drug release pattern, with loading dose released within 30 min and floating multiple
matrix tablets provided zero order sustained release profile for 12 h. It is concluded that floating
multiple matrix tablets designed were particularly suitable as gastro retentive drug delivery system with
anomalous non-fickian diffusion mechanism. The stability studies showed no significant change in dissolution
profiles (f2 value > 50).