Effect of Surfactants on Oral Delivery of Nanoemulsions Containing Fexofenadine, a Substrate for P-glycoprotein

Nanoemulsions are considered to have an advantage in improving the oral bioavailability of poorly absorbed drugs. However, studies on additives such as surfactants used as emulsifiers, essential for the preparation of nanoemulsions, are relatively limited, and their safety and usefulness require further investigation. In this study, the utility of polyoxyethylene sorbitan monostearate (PS60) and polyglyceryl-10 oleate (PGFE), used as nonionic surfactants, was evaluated by using them as emulsifiers for nanoemulsions containing fexofenadine (FXD), a P-glycoprotein (P-gp) substrate. The median diameter of droplets in FXD nanoemulsions was smaller with PGFE compared with PS60. In the drug release study, all FXD nanoemulsions suppressed the drug release at gastric pH and the cumulative amount of drug released increased at intestinal pH. In an in vivo study, PS60-containing nanoemulsions exhibited a higher area under the plasma concentration-time curve, indicating their potential as an effective formulation for improving the gastrointestinal absorption of FXD. In PS60-containing nanoemulsions, we hypothesize that the absorptive transport of FXD was increased due to the combined effects of improved drug dissolution properties, increased paracellular and/or transcellular transport due to emulsification, and decreased secretory transport due to inhibition of P-gp. In PGFE-containing nanoemulsions, the increased bioavailability of the P-gp substrate drug was lower than PS60-containing nanoemulsions. However, data indicate that PGFE has a weaker P-gp inhibitory potential than PS60 in the cellular transport of digoxin, and it may serve as a surfactant with minimal P-gp interaction in the gastrointestinal tract when used in combination with P-gp substrate drugs.