Formulation optimization and bioavailability after oral and nasal administration in rabbits of puerarin-loaded microemulsion.

The main objective of the study was to investigate the efficacy of microemulsion (ME) to facilitate bioavailability of puerarin (PUE) after oral and nasal administration. The pseudo-ternary phase diagrams were constructed to screen the ME components and optimize the ME formulation. The optimized formulation for bioavailability assessment consisted of 20% Tween 80, 20% glycerin, and 1.6% ethyl oleate. The solubility (27.8 mg/mL) of PUE in ME was significantly improved compared to that (4.58 mg/mL) of crude PUE in water. The ME droplets were spherical with a mean particle diameter of 23.4 nm. After nasal (5 mg/kg) and oral (20 mg/kg) administration of a single dose of PUE as ME to fasted rabbits, the absolute bioavailability was 34.58% and 13.54%, respectively. It showed a shorter T(max) (0.75 h) for nasal administration than that (1.0 h) for oral administration of PUE-loaded ME. The C(max) of PUE-loaded ME was 0.55 μg/mL after nasal administration and 0.64 μg/mL after oral administration, respectively. The results showed that nasal administration might be a promising route to enhance the absorption of PUE in the form of ME.