1. Comparisons in included studies.

Intervention	Control (no NAC)	Reference
NAC 600 mg orally twice daily plus amoxicillin 1000 mg twice daily, omeprazole 20 mg twice daily and clarithromycin 500 mg twice daily	Same regimen, placebo controlled	Hamidian 2015
NAC 600 mg orally twice daily plus amoxicillin 500 mg four times daily, bismuth citrate 120 mg four times daily, omeprazole 20 mg twice daily, and clarithromycin 500 mg twice daily	Same regimen, without placebo	Emami 2014
NAC 400 mg orally twice daily plus sequential therapy with rabeprazole 20 mg and amoxicillin 1g (both twice daily) for the first five days, followed by rabeprazole 20 mg, clarithromycin 500 mg and metronidazole 500 mg (all drugs twice daily) for the remaining five days	Same regimen, without placebo	Yoon 2014
NAC 600 mg orally twice daily plus ciprofloxacin 500 mg twice daily, pantoprazole 40 mg twice daily and bismuth subcitrate 120 mg two tablets twice daily	Same regimen, placebo controlled	Karbasi 2013
NAC 600 mg orally once a day for one week before a culture‐guided regimen, including a proton pump inhibitor (PPI) plus two antibiotics	Same regimen, without placebo	Cammarota 2009
NAC 400 mg orally three times a day plus clarithromycin 500 mg twice daily and lansoprazole 30 mg twice daily	Same regimen, without placebo	Gurbuz 2005
NAC 600 mg orally twice daily plus omeprazole 40 mg twice daily and amoxicillin 750 mg twice daily	Same regimen, without placebo	Zala 1994
NAC 600 mg orally three times a day plus amoxicillin 375 mg three times a day	Same regimen, placebo controlled	Hansen 1994

NAC: N‐acetylcysteine