Controlled release of glaucocalyxin–a self-nanoemulsifying system from osmotic pump tablets with enhanced bioavailability

Objective: The purpose of this study was to develop a new formulation to enhance the bioavailability simultaneously with controlled release of glaucocalyxin A (GLA). Material and methods: In this study, controlled release of GLA was achieved by the osmotic release strategy taking advantage of the bioavailability enhancing capacity of self-nanoemulsifying drug delivery systems (SNEDDS). The formulation of GLA-SNEDDS was selected by the solubility and pseudoternary-phase diagrams studies. The prepared GLA-SNEDDS formulations were characterized for self-emulsification time, effect of pH and robustness to dilution, droplet size analysis and zeta potential. The optimized GLA-SNEDDS were used to prepare GLA-SNEDDS osmotic pump tablet via direct powder compression method. The effect of formulation variables on the release characteristic was investigated. GLA-SNEDDS osmotic pump tablets were administered to beagle dogs and their pharmacokinetics were compared to GLA and GLA-SNEDDS as a control. Results: In vitro drug release studies indicated that the GLA-SNEDDS osmotic pump tablet showed sustained release profiles with 90% released within 12 h. Pharmacokinetic study showed steady blood GLA with prolonged T_max and mean residence time (MRT), and enhanced bioavailability for GLA-SNEDDS osmotic pump tablet. Conclusion: It was concluded that simultaneous controlling on GLA release and enhanced bioavailability had been achieved by a combination of osmotic pump tablet and SNEDDS.