High quality bowel preparation is crucial for an effective examination of the colon during colonoscopy. Diabetes, chronic constipation, spinal cord injury, and the use of medications such as narcotics and tricyclic antidepressants are well known predictors of inadequate bowel preparation. The 2014 US Multi-Society Task Force guidelines do not recommend the use of a specific bowel regimen in high risk patients, and limits its statement to the favorable use of additional purgatives in this group of patients (weak recommendation, low quality evidence). We aimed to identify the rate of inadequate bowel preparation in high risk patients and to compare the efficacy of different types of bowel preparations in this population. We identified colonoscopies (n=3651) performed at our institution between January 2019 until November 2019. Patients at high risk for inadequate preparation were identified by specific ICD-10 codes for constipation, diabetes or spinal cord injury or by review of outpatient pharmacy orders for narcotics, antidepressants or laxatives. Bowel preparation adequacy was reported according to the 4- point Boston Bowel Preparation Scale. Mid-P Exact test was used to compare the rates of poor bowel preparation in constipated patients according to the bowel preparation received. The majority of patients were male (92.3%) with a mean age of 64.2+10.4. Approximately 65% of patients received a split dose PEG electrolyte solution with ascorbic acid (Moviprep), 25% received 1 week of PEG 3350 (Miralax) prior to a split dose Moviprep or PEG electrolyte solution (Golytely), and 9.5% prepped with Golytely. Overall, 680 colonoscopies (18.6%) had inadequate bowel preparation of which 235 (6.4%) were deemed poor. A total of 2166 colonoscopies (59.3%) were performed on high risk patients (table). Among high risk patients, the rate of inadequate bowel preparation was 24.5% (figure). In a subgroup analysis on patients with constipation who were prescribed laxatives (n=984), the rate of poor bowel preparation was significantly reduced in patients who received 1 week of Miralax followed by split dose Moviprep or Golytely (13.9%) compared to Split dose Moviprep or Golytely alone (19.9%) OR= 0.65( 95% CI: 0.46-0.91, p=0.006). High risk patients have an increased rate of inadequate bowel preparation. One week of Miralax followed by split dose Moviprep or Golytely reduced the rate of poor bowel preparation in constipated patients on laxatives. If proven beneficial in large randomized controlled trials, this method of preparation will reduce repeated colonoscopies and wasted capacity in endoscopy unit.View Large Image Figure ViewerDownload Hi-res image Download (PPT)