Chitosan-modified cholesterol-free liposomes for improving the oral bioavailability of progesterone.

Based on the structurally similar properties of progesterone and cholesterol, chitosan-coated cholesterol-free liposomes (CS-Lipo/Prog) were formulated. CS-Lipo/Prog are spherical and uniform in size (662.1±19.3nm) with positive potential (28.19±1.97mV). The average drug entrapment efficiency (EE) is approximately 80%. The in vitro release profile of CS-Lipo/Prog shows sustained release. The in vitro stability evaluation demonstrated that CS-Lipo/Prog can efficiently shield Prog from degradation in the gastrointestinal tract. CS-Lipo/Prog showed a longer MRT and higher AUC after oral administration to mice than in the control group (progesterone-free). The relative bioavailability of CS-Lipo/Prog was higher than that of progesterone soft capsules (QINING) and Lipo/Prog. Collectively, these findings suggest that cholesterol-free chitosan-coated liposomes are a promising alternative for improving the oral bioavailability of progesterone.