A placebo-controlled, randomised pilot trial of N-acetylcysteine or placebo for cessation of tobacco smoking.

Smoking represents a significant health threat to the population, however there remains a core group of consistent smokers that are largely unable to break the addiction. Novel therapies are required to assist this group with cessation. N-acetylcysteine (NAC) is a nutraceutical supplement that has shown efficacy compared to placebo in previous pilot studies for assisting smokers to quit or reduce their consumption of cigarettes. A double-blind, randomised trial with a treatment period of 16 weeks and a final follow-up at 42 weeks was conducted comparing 1.8g of effervescent NAC per day (n=47) with placebo (n=47) as an aide to smoking cessation. Both study arms received adjunctive online support through the QuitCoach program. Participants reported smoking at each timepoint (baseline and weeks 8, 16 & 42), which was confirmed through salivary cotinine and exhaled carbon monoxide testing. Primary and secondary analyses were undertaken using a modified intent-to-treat basis, including all participants with at least one valid post baseline outcome, regardless of treatment received or their withdrawal from the study. There was no significant difference in smoking outcomes between intervention groups among the 24 participants that competed follow-up. There were no significant differences in age, gender, or body mass index (BMI) between the groups lost to follow-up or recorded at follow-up. This study found no evidence to support NAC as a therapy for smoking cessation. The negative outcome could be the result of lack of treatment efficacy, or alternatively, small sample size, participant retention difficulties, dose, or duration of follow-up. Trial Registration: Australian New Zealand Clinical Trials registry (ANZCTR), ACTRN12617001478303. Registered on 19 October 2017.