Mucoadhesive Gastroretentive Poly (ε-caprolactone) Microspheres for Sustained Release of Acyclovir: Formulation and Characterization

Introduction: Acyclovir is an antiviral drug used to treat herpes simplex keratitis, herpes simplex blepharitis, herpes simplex labialis, and other viral diseases. In the current work, the medication acyclovir, which is classified as BCS class III, was effectively incorporated using the solvent evaporation approach into polycaprolactone mucoadhesive microspheres. Additionally, polycaprolactone was used for the formulation of mucoadhesive microspheres for acyclovir. Methods: Polycaprolactone microspheres loaded with acyclovir were prepared by the w/o/w double emulsion solvent evaporation technique. Drug encapsulation in microspheres was verified using DSC and FTIR analyses. In vitro release studies showed that acyclovir was released continuously and in a sustained manner for up to 24 hours. The resulting microspheres had a consistent shape and were nearly spherical. Results: All of the microsphere formulations’ release patterns fit the Higuchi model, which indicates that the drug is released from granular and homogeneous matrix systems. After 30 days, it was observed that the microsphere formulations were fairly stable at 4 ± 2°C and 25 ± 2°C/60 ± 5% RH. Discussion: This work effectively illustrates the capability of poly(ε-caprolactone) (PCL)-based mucoadhesive microspheres for the prolonged release of acyclovir. The microspheres demonstrated excellent mucoadhesive properties, favorable particle size distribution, and good drug entrapment efficiency when prepared using a double emulsion solvent evaporation process. In contrast to the rapid release profile of conventionally sold tablets, the optimized formulation (F3) produced extended drug release over a 24-hour period, which is a considerable improvement. Conclusion: The drug release kinetics followed the Higuchi model, and a diffusion-erosion-based release pattern was confirmed by Korsmeyer-Peppas analysis, showing a non-Fickian diffusion mechanism. Overall, this formulation approach could provide a useful foundation for enhancing the functionality of other drugs with similar biopharmaceutical limitations.