Efficacy of simethicone and N-acetylcysteine as premedication in improving visibility during upper endoscopy

Summary Background Simethicone and N‐acetylcysteine have been widely used in improving endoscopic visibility. However, the optimal dose, volume, and dosing time for the premedication regimen are still unclear. Aim Our aim was to assess the efficacy of premedication in improving endoscopic visibility and determine the contributions of dose, volume, and premedication time. Methods A total of 1849 patients were prospectively treated in three groups: group A: 100‐mg simethicone suspension in 5 mL water; group B: 100‐mg simethicone suspension in 100 mL water; and group C: 100‐mg simethicone suspension in 100 mL water containing 200 mg N‐acetylcysteine. Mucosa visibility was assessed at seven sites of upper gastrointestinal tract. The sum of scores was considered as total mucosal visibility score (TMVS). Results The upper body of stomach had the worst visibility score for all groups. TMVS of groups B and C were significantly lower than those of group A. Group C had a significantly fewer patients requiring endoscopic flushing than groups A and B. The TMVS for groups B and C were significantly lower than for group A within 30 min of beginning premedication. Beyond 30 min of premedication, there was no significant difference in the TMVS among groups. Conclusions Premedication using 100 mg simethicone in 100 mL of water improves endoscopic visibility. Addition of N‐acetylcysteine to simethicone in 100 mL of water reduces the need for endoscopic flushing. For patients unable to tolerate a large fluid volume, a 5‐mL simethicone suspension administered more than 30 min prior to upper endoscopy is suggested.