Fetal Concentrations of Budesonide and Fluticasone Propionate: a Study in Mice

The study goal was to evaluate the transplacental transfer of two corticosteroids, budesonide (BUD) and fluticasone propionate (FP), in pregnant mice and investigate whether P-glycoprotein (P-gp) might be involved in reducing BUD transplacental transfer. Pregnant mice ( N = 18) received intravenously either low (104.9 μg/kg) or high (1049 μg/kg) dose of [ 3 H]-BUD or a high dose of [ 3 H]-FP (1590 μg/kg). In a separate experiment, pregnant mice ( N = 12) received subcutaneously either the P-gp inhibitor zosuquidar (20 mg/kg) or vehicle, followed by an intravenous infusion of [ 3 H]-BUD (104.9 μg/kg). Total and free (protein unbound) corticosteroid concentrations were determined in plasma, brain, fetus, placenta, kidney, and liver. The ratios of free BUD concentrations in fetus versus plasma K (fetus, plasma, u, u) 0.42 ± 0.17 (mean ± SD) for low-dose and 0.38 ± 0.18 for high-dose BUD were significantly different from K = 1 ( P