Effective colon cleansing without compromising patient comfort is regarded as a prerequisite to achieving optimal, safe investigation of the large bowel.^1–3 In the UK, France and Canada, poor bowel preparation prevents completion of colonoscopies in approximately 20–30% of failed procedures.^2,3 Although many clinical trials have investigated the efficacy and safety of available bowel-cleansing agents, it remains unclear which is the best therapeutic option.^2–4

There is a wide variety of bowel cleansing agents available in Europe and they generally fall into one of three groups.^2,3 The first group is the low-volume osmotic laxatives, such as magnesium citrate and sodium phosphates. These act by drawing extracellular fluid across the bowel wall into the lumen by osmosis. Fluid accumulation produces distension, which promotes peristalsis and bowel evacuation. Another group is the high-volume osmotic laxatives, which are preparations of polyethylene glycol administered with a high volume of a dilute electrolyte solution. The electrolyte solution is retained in the lumen due to the osmotic effect of the polymer, and this promotes peristalsis and evacuation, as with low-volume osmotic laxatives. There is little fluid exchange across the bowel wall with high-volume osmotic laxatives, thereby limiting the potential for systemic electrolyte disturbance. However, the high volume of these laxatives decreases compliance and is associated with nausea and bloating. The third group of bowel-cleansing agents is the stimulant laxatives, such as sodium picosulphate and bisacodyl. These are low-volume agents that work principally by enhancing intestinal motility, and so are often associated with abdominal cramping; they also increase the amount of fluid in the bowel by a low-grade inflammatory effect. There are also preparations that combine agents from more than one of these three groups, most usually the combination of a stimulant and a low-volume osmotic laxative. In theory, combining different laxatives with complementary mechanisms of action should enhance efficacy while avoiding an adverse impact on tolerability that could be associated with an increased dose of a single agent alone. A welltolerated preparation that is easy to administer in accordance with the manufacturer’s instructions should also encourage compliance and therefore maximise efficacy. One bowel-cleansing agent that has been in widespread clinical use in the UK and the Republic of Ireland since the 1980s is the low-volume oral combination of sodium picosulphate (a stimulant laxative) and magnesium citrate (an osmotic laxative), which is marketed as Picolax® (Ferring). This combination has recently been approved for use in these and other countries in the EU as CitraFleet® (Casen-Fleet, Eisai).

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