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

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.