Colon cleansing preparations can be broadly classified into three groups. Osmotic laxatives such as sodium phosphate (NaP) increase colon water content by attracting extracellular fluid efflux through the bowel wall. Polyethylene glycol (PEG) laxatives are high molecular weight non-absorbable polymers that are administered in a dilute electrolyte solution, this is retained in the colon where it acts as a bowel cleanser without any significant fluid exchange across the colonic mucosa. The third group are stimulant laxatives such as senna or sodium picosulphate which work primarily by enhancing smooth muscle contractility and also they may increase bowel water content.