The study was carried out as a randomised, single-blind, active-controlled, multi-centric, phase III study with two parallel treatment groups. The primary efficacy criterion was the frequency of effective gut cleansing in each of the two treatment groups (grade A or B "overall quality of gut cleansing" as judged by a blinded expert panel on the basis of videotapes recorded during the endoscopic procedure).

The study was designed as a randomised, active-controlled, single-blind, multi-centre, pivotal phase III trial with two parallel treatment groups. 15 German hospitals with specialised gastroenterology units were expected to participate in the investigation.

Up to 360 hospital in-patients routinely scheduled to undergo complete colonoscopy were to be enrolled one to two days prior to the endoscopic procedure, and to be randomly allocated to one of the two treatment arms in a ratio of 1:1. Bowel preparation was performed using equal split doses of either low-volume NRL994 (two doses of 1,000 mL each) or high-volume PEG+E (two doses of 2,000 mL each). The first dose was to be taken in the evening before the procedure, the second dose on the morning of the day of the colonoscopy. The patients allocated to NRL994 were asked to drink at least 1L of additional clear liquid in addition to the study drug. During colonoscopy the cleansing of each of the five pre-defined gut segments was to be assessed by the physician performing the examination, using a 5-level verbal rating scale. Videotapes were to be recorded of all procedures in order to allow central review by a blinded and independent expert panel whose ratings were the primary basis for the analysis of efficacy. The patients enrolled in the study were asked to fill in a questionnaire concerning the acceptability of the preparation. A patient's participation in the study was terminated upon completion of the intervention by performing a final examination and filling in the study termination page. No interim analysis was to be performed.

Inclusion Criteria:

• written informed consent prior to inclusion;
• male or female in-patients, aged 18 to 85 years, with indication for complete colonoscopy;
• willing and able to complete the entire procedure and to comply with study instructions;
• females of childbearing potential employing an adequate method of contraception.

Exclusion Criteria:

• ileus;
• intestinal obstruction or perforation;
• toxic megacolon;
• congestive heart failure (NYHA class III and IV);
• acute life-threatening cardiovascular disease;
• untreated or uncontrolled arterial hypertension (SBP max>170mmHg, DBP min>100mmHg);
• severe renal failure;
• severe liver failure;
• known glucose-6-phosphatase dehydrogenase deficiency;