Background
/Aims: Divided-dose oral sodium phosphate laxative is recommended for bowel cleansing before colonoscopy. Patients need information about the onset and duration of activity of the preparation. This study was designed to develop practical prescribing information for the patients to reduce anxiety and insomnia concerning bowel movement, Methods: one hundred ninety patients were requested to take 45 mL sodium phosphate in the previous evening and the morning of the procedure, and to complete a questionnaire. The overall quality of bowel cleansing were assessed by endoscopists. Results: Bowel activity began 2,25 (90 percentile: 3.58) hours after the first dose and continued for 6.55 (90 percentile: 8.5) hours. For the second dose the time of onset was 0.85 (90 percentile: 1,67) hours, and bowel activity continued for 3,6 (90 percentile: 5.17) hours. Conclusions: The onset of bowel activity from the first dose of sodium phosphate starts within 4 hours and it is completed within 8,5 hours for most. We can recommend the patients to take the first dose of NaP solution at 4 p.m. of the previous day of the exam and second dose more than 5 hours earlier before the colonoscopy in the care that the onset of the bowel activity after the first dose take longer than 4 hours. (Korean J Gastrointest Endosc 2001;23:88-92)