Like other topical corticosteroids, halobetasol propionate has anti-inflammatory, antipruritic and vasoconstrictive actions. The mechanism of the anti- inflammatory activity of the topical corticosteroids, in general, is unclear However, corticosteroids are thought to act by the induction of phospholipase A 2 inhibitory proteins , collectively called lipocorins It is postulated that these proteins control the biosynthesis of potent mediators of inflammation such as prostaglandins and leukotrienes by inhibiting the release of their common precursor arachidonic acid Arachidonic acid is released from membrane phospholipids by phospholipase A 2 .
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 .