Sodium phosphate is one of the bowel preparation regimens for colonoscopy. However, intraluminal gas can impair visibility during the examination. Simethicone is medication that works by reducing the surface tension of air bubbles. We aimed to evaluate the effect of simethicone in enhancing visibility and efficacy during colonoscopy.

A prospective, randomized, double-blinded, placebo-controlled study was conducted. One hundred and twenty-four patients were allocated to receive 2 dosages of either 45 ml of sodium phosphate plus 240 mg of simethicone tablets or 45 ml of sodium phosphate plus placebo in the evening before and in the morning of the procedure day. The colonoscopic examination was recorded. Visibility was blindly assessed for the amount of air bubbles and the degree of haziness by a single investigator. Five areas of the colon were graded for the amount of air bubbles, from 0 to 3; grade 0 and 1 were defined as the diminishing of air bubbles. The haziness was graded into 5 levels from excellent to unacceptable. Excellent, good and adequate were defined as the diminishing of haziness. The total duration of colonoscopy, the side effect of medication and the endoscopist and patient satisfaction were compared between 2 groups. Endoscopist satisfaction was evaluated by questionnaires. Visual analog scale (0-10) was used for rating patient satisfaction and the side effect of medication.

Inclusion Criteria:

- Patients with age 18-70 yrs old who undergo colonoscopy at the endoscopic unit of the hospital

Exclusion Criteria:

• Renal insufficiency (Cr >2.3 mg/dl)
• Congestive heart failure
• Massive ascites
• Acute myocardial infarction within 6 months
• Coagulopathy
• Previous colonic surgery
• Suspected of colonic obstruction Pregnancy Refuse to give inform consent