The goal of this randomized controlled trial is to compare the safety, compliance, and efficacy of different bowel preparation methods prior to colonoscopy. Researchers will compare 4-L split-dose polyethylene glycol and the bisacodyl + docusate sodium regimen versus 2-L split-dose polyethylene glycol plus oral simethicone regimen versus the conventional method for bowel preparation before colonoscopy. Participants will undergo history-taking, clinical examination, laboratory investigations, and colonoscopy. Patients will be randomly assigned to receive 4-L split-dose polyethylene glycol and bisacodyl + docusate sodium, a 2-L split-dose polyethylene glycol regimen plus oral simethicone, or 2-L split-dose polyethylene glycol alone as a control. Colonoscopy will be done 24 hrs after the start of medication. Researchers will assess the quality of the bowel preparation using the Aronchick bowel preparation scale. Researchers will also assess the number of adverse events and ask the patients about the ease of bowel preparation administration, tolerability of preparation regimen, and willingness to take the same agent again for a repeat colonoscopy in the future.

Inclusion Criteria:

• Patients undergoing colonoscopy as a day-care procedure for various indications (lower GI bleeding, colorectal cancer screening, altered bowel habits, etc.)
• Patients of either sex aged >18 years and <70 years.
• Patients willing to give written informed consent.

Exclusion Criteria:

• Presence of Renal failure, cirrhosis, ascites, CCF, bleeding disorders, seizure disorder, gastrointestinal obstruction, or perforation.
• History of serious adverse events to other electrolyte-based colonic lavages.
• Female patients who are pregnant or lactating or considering pregnancy.
• Allergy.