Mometasone furoate increased chromosomal aberrations in an in vitro Chinese hamster ovary-cell assay, but did not increase chromosomal aberrations in an in vitro Chinese hamster lung cell assay. Mometasone furoate was not mutagenic in the Ames test or mouse- lymphoma assay, and was not clastogenic in an in vivo mouse micronucleus assay and a rat bone marrow chromosomal aberration assay or a mouse male germ -cell chromosomal aberration assay. Mometasone furoate also did not induce unscheduled DNA synthesis in vivo in rat hepatocytes.
The precise mechanism through which fluticasone propionate affects rhinitis symptoms is not known. Corticosteroids have been shown to have a wide range of effects on multiple cell types (., mast cells, eosinophils, neutrophils, macrophages, lymphocytes) and mediators (., histamine, eicosanoids, leukotrienes, cytokines) involved in inflammation. In 7 trials in adults, fluticasone propionate nasal spray has decreased nasal mucosal eosinophils in 66% of patients (35% for placebo) and basophils in 39% of patients (28% for placebo). The direct relationship of these findings to long-term symptom relief is not known.