An in vitro and clinical dose-finding study of antifoaming effects of simethicone during colonoscopy.

Abstract

Simethicone is an antifoaming agent frequently added to endoscopic rinse solutions but has recently been implicated as a risk factor for transmission of infections due to the formation of simethicone deposits within scope channels. Since the build-up of residue is likely dose-related, the smallest effective dose of simethicone should be used but there are no data available on the effective dose. Thus, we conducted a dose-finding study in an "in vitro bubble model" to determine the appropriate simethicone dose. Six 100-mL test tubes were filled with a 1% (v/v) solution of kitchen detergent (Fairy®, Procter & Gamble,London, England) in water for irrigation (Baxter®, Sydney, Australia). One test tube served as the control, while different doses of simethicone (Infacol®, Nice Pak, Melbourne, Australia) were added to the other five tubes (0.02, 0.2, 2.0, 20, and 200mg/100mL). Oxygen was streamed for 30s into the test tubes at a rate of 2L/min. After 10s, photographs were taken and the visiblebubbles were semi-quantitatively rated by independent assessors blinded to the dosing of simethicone. Simethicone at doses of 2mg/100mL had no appreciable antifoaming effect, whereas concentrations ≥ 20mg/100mL were sufficient to suppress bubble formation. This is substantially lower compared with frequently used doses of up to 200mg/100mL. Subsequently, we tested the lower simethicone dose with previously used higher doses, in 1475 and 1340 patients, respectively. We found it to have no impact on polyp detection with a rate of 56.7% (54.2-59.3% [95% CI]) at the lower dose and 56.5% (53.8-59.1% [95% CI]) at the higher dose.