AIM To evaluate the efficacy of 5 m L simethicone solution in decreasing gastric foam if given at least 30 min before gastroscopy.METHODS This was a randomized, placebo controlled, endoscopist blinded study performed at Changi General Hospital. Patients were at least 21 years old, had no prior sur-gical resection of the upper gastrointestinal tract, and scheduled for elective diagnostic gastroscopies. The primary outcome was the total mucosal visibility score(TMVS) which was evaluated using Mc Nally score. The sample size was calculated to be 24 per group(SD 2.4, 80% power, P < 0.05, 2-sample t test). RESULTS Fifty-four patients were randomised to receive either simethicone [1 m L liquid simethicone(100 mg) in 5 m L of water] or placebo(5 m L of water) at least 30 min before their gastroscopy. Six accredited consultants conductedthe gastroscopy, and the interobserver agreement of scoring TMVS was good with a Kappa statistic of 0.73. The simethicone group had significantly better mean TMVS compared to placebo(5.78 ± SD 1.65 vs 8.89 ± SD 1.97, P < 0.001). The improvement was statistically significant for the duodenum and the gastric antrum, angularis, body, and fundus. Percent 51.9 of patients in the simethicone group had a TMVS of 4(no bubbles at all) to 5(only 1 area with minimal bubbles), while in the placebo group 3.7% of patients had TMVS of 4 or 5. The number needed to treat was 2.1 to avoid a TMVS of 6 and more. The simethicone group also had a significantly shorter procedure time with less volume of additional flushes required during gastroscopy to clear away obscuring gastric foam.CONCLUSION With a premedication time of at least 30 min, 5 m L simethicone can significantly decrease gastric foam, decrease the volume of additional flushes, and shorten gastroscopy time. AIM To evaluate the efficacy of 5 mL of simethicone solution in decreasing gastric foam if given at least 30 min before gastroscopy. METHODS This was a randomized, placebo controlled, endoscopist blinded study performed at Changi General Hospital. Patients were at least 21 years old, had no prior sur-gical resection of the upper gastrointestinal tract, and scheduled for elective diagnostic gastroscopies. The primary outcome was the total mucosal visibility score (TMVS) which was evaluated using Mc Nally score. The sample size was calculated to be 24 per group (SD 2.4, 80% power, P <0.05, 2-sample t test). RESULTS Fifty-four patients were randomized to either either simethicone [1 m L liquid simethicone (100 mg) in 5 m L of water] 5 mL of water) at least 30 min before their gastroscopy. Six accredited consultants conducted the gastroscopy, and the interobserver agreement of scoring TMVS was good with a Kappa statistic of 0.73. The simethicone group had significantly better mean T MVS compared to placebo (5.78 ± SD 1.65 vs 8.89 ± SD 1.97, P <0.001). The improvement was statistically significant for the duodenum and the gastric antrum, angularis, body, and fundus. Percent 51.9 of patients in the simethicone group had a TMVS of 4 (no bubbles at all) to 5 (only 1 area with minimal bubbles), while in the placebo group 3.7% of patients had TMVS of 4 or 5. The number needed to treat was 2.1 to avoid a TMV of 6 and more. The simethicone group also had a significantly shorter procedure time with less volume of additional flushes required during gastroscopy to clear away obscuring gastric foam. CONCLUSION With a premedication time of at least 30 min, 5 m L simethicone can significantly reduce gastric foam, decrease the volume of additional flushes, and shorten gastroscopy time.