Enhanced bioavailability of total paeony glycoside by self-microemulsifying drug delivery system

Total paeony glycoside (TPG) is extracted and purified from a traditional Chinese herbal medicine.  It has many biological and pharmacological activities.  However, there are few dosage forms of TPG in the market because of its low bioavailability.  Self-microemulsifying drug delivery system (SMEDDS) is a vital tool in solving low bioavailability of poor absorption drugs.  So the objective of this study is to develop a new TPG-SMEDDS for the oral delivery of poorly soluble TPG.  Through the construction of pseudo-ternary phase diagrams, the optimum prescription was obtained, which consisted of 18.70% TPG, 16.27% ethyl oleate as oil, 43.34% Cremophor RH40 as surfactant and 21.73% Transcutol P as cosurfactant.  The characterizations of TPG-SMEDDS including morphological characterization, droplet size, zeta-potential, emulsi?cation time, and dissolution study of TPG-SMEDDS were evaluated.  The results showed that TPG-SMEDDS is stable and its release rate is high in four different media (0.1 mol·L⁻¹ HCl, pH 6.8 PBS, pH 7.4 PBS, and water).  The relative bioavailability of SMEDDS was dramatically enhanced in an average of 1.52-fold that of TPG-suspension.  It is concluded that the bioavailability of TPG is enhanced greatly by SMEDDS.