Fluticasone propionate is a highly selective agonist at the glucocorticoid receptor with negligible activity at androgen , estrogen , or mineralocorticoid receptors , thereby producing anti-inflammatory and vasoconstriction effects. It has been shown to have a wide range of inhibitory effects on multiple cell types (. mast cell , eosinophil , neutrophil , macrophages , and lymphocytes ) and mediators (. histamine , eicosanoids , leukotrienes , and cytokines ) involved in inflammation . Fluticasone propionate is stated to exert a topical effect on the lungs without significant systemic effects at usual doses, due to its low systemic bioavailability .
No metabolites of fluticasone propionate were detected in an in vitro study of radiolabeled fluticasone propionate incubated in a human skin homogenate. The total blood clearance of systemically absorbed fluticasone propionate averages 1,093 mL/min (range, 618 to 1,702 mL/min) after a 1-mg intravenous dose, with renal clearance accounting for less than % of the total. Fluticasone propionate is metabolized in the liver by cytochrome P450 3A4-mediated hydrolysis of the 5- fluoromethyl carbothioate grouping. This transformation occurs in 1 metabolic step to produce the inactive17-ÃŸ-carboxylic acid metabolite, the only known metabolite detected in man. This metabolite has approximately 2,000 times less affinity than the parent drug for the glucocorticoid receptor of human lung cytosol in vitro and negligible pharmacological activity in animal studies. Other metabolites detected in vitro using cultured human hepatoma cells have not been detected in man.
In rabbits, fetal weight reduction and cleft palate were observed at a fluticasone propionate dose approximately times the MRHDID for adults (on a mg/m² basis at a maternal subcutaneous dose of 4 mcg/kg/day). However, no teratogenic effects were reported at fluticasone propionate doses up to approximately 20 times the MRHDID for adults (on a mg/m² basis at a maternal oral dose up to 300 mcg/kg/day). No fluticasone propionate was detected in the plasma in this study, consistent with the established low bioavailability following oral administration [see CLINICAL PHARMACOLOGY ].