Enhanced oral bioavailability of acyclovir by inclusion complex using hydroxypropyl-β-cyclodextrin

The therapeutic potential of acyclovir is limited by the low oral bioavailability owing to its limited aqueous solubility and low permeability. The present study was a systematic investigation on the development and evaluation of inclusion complex using hydroxypropyl-beta-cyclodextrin for the enhancement of oral bioavailability of acyclovir. The inclusion complex of acyclovir was prepared by kneading method using drug: hydroxypropyl-beta-cyclodextrin (1: 1 mole). The prepared inclusion complex was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, NMR spectroscopy and evaluated in vitro by dissolution studies. In vivo bioavailability of acyclovir was compared for inclusion complex and physical mixture in rat model. Phase solubility studies indicate the formation of acyclovir-hydroxypropyl-beta-cyclodextrin complex with higher stability constant and linear enhancement in drug solubility with increase in hydroxypropyl-beta-cyclodextrin concentration. Characterization of the prepared formulation confirms the formation of acyclovir-hydroxypropyl-beta-cyclodextrin inclusion complex. Dissolution profile of inclusion complex demonstrated rapid and complete release of acyclovir in 30 min with greater dissolution efficiency (90.05 +/- 2.94%). In vivo pharmacokinetic data signify increased rate and extent of acyclovir absorption (relative bioavailability similar to 160%; p<0.0001) from inclusion complex, compared to physical mixture. Given the promising results in the in vivo studies, it can be concluded that the inclusion complex of acyclovir could be an effective and promising approach for successful oral therapy of acyclovir in the treatment of herpes viruses.