CHANGES IN NASAL NITRIC-OXIDE CONCENTRATION ASSOCIATED WITH SYMPTOMS OF COMMON COLD AND TREATMENT WITH A TOPICAL NASAL DECONGESTANT

Nitric oxide (NO) is known to play a role in the non-specific host def ence mechanism. Furthermore, it has been proposed that NO may be impor tant in respiratory defence against the viruses which cause the common cold. Indeed, elevated NO levels have previously been observed in ora lly expired air during upper respiratory tract infection (URTI), We wa nted to investigate further the role of NO in the host response to URT I. Total nasal airway resistance (tNAR) and nasal NO levels were obtai ned during symptomatic URTI in 97 subjects. Of these, 80 received trea tment with either oxymetazoline or a placebo spray. Post-treatment tNA R and NO levels were obtained 60 min after treatment. Measurements of NO were also repeated 4-6 weeks later, when subjects were healthy, (n = 82). NO levels were measured using a chemiluminescence gas analyser whilst tNAR was measured using posterior rhinomanometry. The mean pre- treatment NO level (1063 +/- 541 ppb) was shown to be reduced signific antly after treatment with oxymetazoline (827 +/- 373 ppb), p < 0.0001 . The mean pre-treatment rNAR, 0.42 Pa cm(-3) sec(-1), was also reduce d significantly to 0.21 Pa Cm-1 sec(-1) (I) < 0.001) after treatment w ith oxymetazoline. There was no significant correlation between the ch ange in NO levels and change in tNAR following treatment with oxymetaz oline (p, corrected for ties = 0.011, p = 0.98). No significant differ ence was found between NO levels obtained during URTI (1130 +/- 444 pp b) when compared to values obtained when healthy (1197 +/- 361 ppb), p = 0.25. These results demonstrate that treatment with a topical nasal decongestant spray causes a reduction in nasal NO levels. We propose that this occurs as an indirect consequence of the vasoconstrictor act ions of oxymetazoline. Since no change in NO levels was observed durin g URTI, we propose that the NO synthase responsible for NO production in the nose responds in a different manner to that in the lungs.