Rice Germ Oil as Multifunctional Excipient in Preparation of Self-Microemulsifying Drug Delivery System (SMEDDS) of Tacrolimus

Surmounting the constraints of limited solubilization efficiency and prime requisite of antioxidant for conventional lipid formulations, the research work explores an edge over formulation utilizing potential applicability of rice germ oil (RGO) as a multifunctional excipient. Self-microemulsifying drug delivery system (SMEDDS) of tacrolimus (TAC) was formulated with RGO, an indigenous source of gamma-oryzanol. Being the same biological source, RGO and rice bran oil (RBO) were compared and it was found that RGO have more solubilization potential for TAC (2.2-fold) as well as higher antioxidant activity (8.06-fold) than the RBO. TAC-SMEDDS was prepared using RGO/Capmul PG8 (2:3) as an oil phase, Cremophore EL as a surfactant, and Transcutol P as a cosurfactant. The approximate particle size of TAC-SMEDDS was found to be 38 nm by dynamic light scattering and 12 nm by small angle neutron scattering. The in vitro dissolution studies showed complete and rapid drug release in 30 min compared to a plain drug (< 5%) and marketed capsule (< 50%). AUC and C (max) were found to be 45.05 +/- 15.64 ng h/ml and 3.91 +/- 1.2 ng/ml for TAC-SMEDDS, 12.59 +/- 5.54 ng h/ml and 0.48 +/- 0.12 ng/ml for plain TAC, and 30.23 +/- 10.34 ng h/ml and 2.31 +/- 0.68 ng/ml for marketed formulation, respectively. The improved pharmacokinetic profile of TAC-SMEDDS is correlating to the dissolution results. Thus, gamma-oryzanol-enriched RGO acts as a potential multifunctional excipient for lipid formulations.