Box-Behnken Design Optimization of Etoposide Loaded Nanoemulsion: Formulation Development, Cellular Uptake Analysis and Pharmacokinetic Evaluation

Etoposide is widely used in the management of different solid tumors as well as leukemias but low aqueous solubility and poor intestinal permeability limit its oral efficacy. The present investigation aimed to enhance the oral bioavailability of etoposide through formation of nanoemulsion employing Box-Behnken design for formulation optimization. The effect of nanoemulsion composition (concentration of labrasol and solutol HS 15) and process parameters (sonication time) on globule size and polydispersity index were investigated. The optimized formulation was found to be with globule size <200 nm and PDI of 0.129. The zeta potential value -35.8 mV for nanoemulsion indicated the formation of a stable colloidal system. The in-vitro release of etoposide from optimized nanoemulsion was conducted with the help of USP dissolution apparatus type-II in 250 ml of gastric fluid of pH = 1.2 and intestinal fluid of pH 6.8 at 37 +/- 0.5 degrees C using dialysis bag. High drug release was achieved in case of nanoemulsion (47.127 +/- 0.82%) as compared to the marketed capsule (25.877 +/- 1.33%) and drug suspension (21.374 +/- 1.69%) in the simulated intestinal fluid of pH 6.8 after 4 h. The developed delivery system exhibited pH-independent dissolution profile of the loaded etoposide. Confocal laser scanning microscopy (CLSM) study of developed nanoemulsion system was done on intestinal tissue of Wistar rats and optical cross sections revealed deeper penetration of Rhodamine B compared to the dye solution. A comparative in-vivo bioavailability profile of developed formulation, marketed product, and API suspension was also investigated after oral administration in Wistar rats. The relative bioavailability of etoposide loaded nanoemulsion system was 2.5 times higher than the drug suspension and 1.7 times higher than the marketed capsule (Posid (R)). The findings of the current investigation proved that the developed nanoemulsion system is helpful to improve the bioavailability of P-gp substrate drugs like etoposide that have low oral absorption.