RESULTS	For high-risk patients ( n = 89 ) , high-dose NAC compared with placebo significantly reduced exacerbation frequency ( 0.85 vs 1.59 [ P = .019 ] and 1.08 vs 2.22 [ P = .04 ] at 8 and 12 months , respectively ) , prolonged time to first exacerbation ( P = .02 ) , and increased the probability of being exacerbation free at 1 year ( 51.3 % vs 24.4 % , P = .013 ) .\