No new trials were found for inclusion in this update. Four studies involving 1943 participants with acute sinusitis met our inclusion criteria. The trials were well-designed and double-blind and studied INCS versus placebo or no intervention for 15 or 21 days. The rates of loss to follow-up were 7%, 11%, 41% and 10%. When we combined the results from the three trials included in the meta-analysis, participants receiving INCS were more likely to experience resolution or improvement in symptoms than those receiving placebo (73% versus %; risk ratio (RR) ; 95% confidence interval (CI) to ). Higher doses of INCS had a stronger effect on improvement of symptoms or complete relief: for mometasone furoate 400 µg versus 200 µg (RR ; 95% CI to versus RR ; 95% CI to ). No significant adverse events were reported and there was no significant difference in the drop-out and recurrence rates for the two treatment groups and for groups receiving higher doses of INCS.
As a glucocorticoid , the lipophilic structure of prednisolone allows for easy passage through the cell membrane where it then binds to its respective glucocorticoid receptor (GCR) located in the cytoplasm. Upon binding, formation of the GC/GCR complex causes dissociation of chaperone proteins from the glucocorticoid receptor enabling the GC/GCR complex to translocate inside the nucleus. This process occurs within 20 minutes of binding. Once inside the nucleus, the homodimer GC/GCR complex binds to specific DNA binding-sites known as glucocorticoid response elements (GREs) resulting in gene expression or inhibition. Complex binding to positive GREs leads to synthesis of anti-inflammatory proteins while binding to negative GREs block the transcription of inflammatory genes. 
Because of the inhibitory effect of corticosteroids on wound healing, a nasal corticosteroid should be used with caution in patients who have experienced recent nasal septal ulcers, recurrent epistaxis, nasal surgery or trauma, until healing has occurred. Although systemic corticoid effects typical of Cushing's syndrome are minimal with recommended doses of topical steroids, this potential increases with excessive doses. If recommended doses are exceeded with long-term use, or if individuals are particularly sensitive, symptoms of hypercorticism could occur including suppression of hypothalamic-pituitary-adrenal function and/or retardation of growth in pediatric patients. Therefore, larger than recommended doses of NASAREL should be avoided.