Apocynin reduced hydrogen peroxide concentration in exhaled breath condensate 60 and 120 minutes after apocynin nebulization comparing to placebo (0.43 μM vs. 0.59 μM and 0.41 μM vs. 0.58 μM respectively, p\<0.05). Interestingly, apocynin caused decrease of NO2- concentration 30, 60 and 120 minutes after apocynin inhalation (3.9 μM vs. 4.5 μM, 3.8 μM vs. 4.5 μM and 3.7 μM vs. 4,4 μM respectively, p\<0.05) comparing to placebo, but did not cause any significant changes in concentration of NO3- in any timepoint (p\>0.05). No influence of apocynin on safety parameters, and no adverse effects has been observed.