Formulation and Evaluation of Gastro Retentive Mucoadhesive Sustained Release Pellets of Acyclovir

Acyclovir is an antiviral drug, belonging to the deoxyguanosine family, widely prescribed for the treatment of herpes simplex viral infections, as well as in the treatment of herpes zoster (shingles). Oral bioavailability of acyclovir is very low (10–20%) owing to its first pass metabolism with elimination half-life (t1/2) of 2-3 h. It has absorption window in upper gastrointestinal tract. Due to its rapid elimination from site of absorption and short biological half life, sustained release formulation system for acyclovir is advantageous. In this study, gastro retentive muco-adhesive SR pellets of acyclovir was prepared using HPMC K 100M as matrix former and Sodium CMC as mucoadhesive polymer by extrusion spheronization technique. Acyclovir pellets prepared with higher concentration of HPMC (batch G) showed in vitro drug release for 12 h with sufficient mucoadhesion strength and ex vivo resident time. Release kinetic studies indicated that drug release data had best fit to Higuchi’s model. In-vivo studies in rat model proved that relative bioavailability of acyclovir SR pellets get increased by 1.98 fold as compared plain drug suspension. The optimized formulation batch G was found to be stable during six months accelerated stability period