Lavage solutions for colonoscopy in adults
A number of lavage solutions are commercially available in Australia. There is no evidence that one preparation is superior to another. The choice of lavage solution should be individualised, taking into consideration the patient’s age, comorbidities, history of constipation, use of opioids, and past colonoscopy preparation outcomes. Bowel preparation regimens vary across different centres; appropriate regimens can be obtained from the endoscopist or, if available, a local hospital protocol.
Adherence is the most important factor affecting the success of bowel preparation. To improve palatability of the preparation, advise the patient to refrigerate the solution, add a flavoured soft drink or cordial, and drink through a straw.
Macrogol 3350 (eg Glycoprep, Glycoprep-C, Moviprep, Plenvu, ColonLYTELY) is an osmotic laxative formulated as a nonabsorbable, osmotically balanced solution that clears the colon without net absorption or secretion of fluid or electrolytes. A small proportion of patients are unable to complete the preparation because of its poor palatability or because they cannot drink the required volume. Macrogol 3350 adverse effects include nausea and vomiting, bloating and abdominal discomfort. It is relatively safe for patients who cannot tolerate large volumes of fluid (eg those with kidney failure, congestive heart failure or decompensated cirrhosis with ascites).
An alternative to macrogol 3350 is a preparation containing the stimulant laxative sodium picosulfate together with citric acid and magnesium oxide (eg Picolax, PicoPrep, Picosalax); these preparations generate magnesium citrate (an osmotic laxative). This is as effective, requires ingestion of smaller volumes of liquid, and may be better tolerated than macrogol 3350. These sodium picosulfate containing preparations may be associated with fluid shifts, dehydration and electrolyte disturbances, so should be used with caution in people with advanced age (eg older than 65 years), and people with kidney or heart disease.
Sodium phosphate–based preparations (eg Phospho-Soda) are hyperosmotic, low-volume osmotic laxatives. They are not a first-line choice because of the increased risk of complications compared to macrogol 3350 and formulations containing sodium picosulfate. Sodium phosphate–based preparations are usually reserved for use in young, healthy people; they are associated with fluid shifts, electrolyte disturbances and worsening renal function, so they should be avoided in people with advanced age (eg older than 65 years), people with kidney or heart disease, people who are dehydrated or have hypercalcaemia, and those taking drugs that affect renal perfusion and function (eg angiotensin converting enzyme [ACE] inhibitors, diuretics, angiotensin II receptor blockers, nonsteroidal anti-inflammatory drugs [NSAIDs]). Sodium phosphate-based preparations cause hyperphosphataemia in up to 40% of healthy subjects, and have been associated with acute phosphate nephropathy.