TOPICAL VASOCONSTRICTOR (OXYMETAZOLINE) DOES NOT AFFECT HISTAMINE-INDUCED MUCOSAL EXUDATION OF PLASMA IN HUMAN NASAL AIRWAYS

Mucosal exudation of almost unfiltered plasma proteins, plasma-derived mediators and fluid has recently been advanced as a major respiratory defence mechanism. Oxymetazoline chloride is a commonly used decongestant agent. By reducing blood flow it may reduce mucosal exudation and thus compromise the mucosal defence capacity. This study examines the effect of topically applied oxymetazoline on histamine-induced plasma exudation into human nasal airways. Twelve normal volunteers participated in a double-blind, randomized, cross-over and placebo-controlled study with pretreatment with a single dose oxymetazoline chloride (5-mu-g or 50-mu-g; a dose previously known to reduce nasal mucosal blood flow by almost 50%) prior to the histamine challenge sequence. Nasal lavages were performed every 10 min for 140 min, and three histamine challenges were performed at 30-min intervals during this period. The concentrations of two exudative indices, N-alpha-tosyl-L-arginine methyl ester (TAME)-esterase activity and albumin, were measured in the nasal lavage fluids. Nasal symptoms (sneezing, nasal secretion and blockage) were assessed by a scoring technique. Histamine induced all three symptoms with correlatively raised levels of the biochemical markers for plasma exudation. Oxymetazoline chloride caused a significant decrease in nasal stuffiness, but did not influence the other nasal symptoms or the histamine-induced plasma exudation. It is concluded that histamine-induced plasma exudation is not influenced by topical oxymetazoline. Thus, an important airway defence reaction such as plasma exudation may be little affected by topical alpha-adrenoreceptor-mediated vasoconstriction. It is further suggested that the antiblockage effect of oxymetazoline can be utilized in nasal research without interfering with the exudative indices which appear on the mucosal surface as a quantitative reflection of the airway tissue involvement in inflammatory processes.