Mechanism of action and toxicities of purgatives used for colonoscopy preparation

Abstract

Importance of the field-In developed countries colonoscopy volume has increased dramatically over the past 15 years and is the principle method used to screen for colon cancer. Preparations used for colon cleaning have evolved over the past 30 years. Some preparations have been shown to be unsafe and are now used on a limited basis. There has been progress on limiting the volume required and on taste improvement.Areas covered in this review-This review provides an account of preparations used from 1980 when polyethylene glycol-based preparations became widely available, until the present day. The review highlights their mechanism of action and principle toxicities. The handling of solutes and solute-free fluid by the colon is also reviewed.What the reader will gain-The reader will gain a perspective on the factors considered in developing colonic purgatives and the rationale for choosing selected preparations based on patient factors such as age, co-morbidities, and concomitant medications.Take home message-Although generally safe and effective, colonic purgatives have both acute and permanent toxicities. The safest preparations utilize polyethylene glycol combined with a balanced electrolyte solution. Limitations of this preparation center on the volume required and poor taste. Alternative formulations are now available; however those using sodium phosphate have fallen out of favor due to a risk of renal toxicity.

A Dual-Action, Low-Volume Bowel Cleanser Administered the Day Before Colonoscopy: Results From the SEE CLEAR II Study

“…Historically, colon cleansing has been routinely performed with solutions containing polyethylene glycol (PEG) and until recently, sodium phosphate ( 13 ). PEG-based preparations preserve the histological features of the colonic mucosa ( 14 ), and have been shown to have an acceptable safety profi le in patients with comorbidities, including serum electrolyte imbalances, infl ammatory bowel disease, hepatic dysfunction, renal failure, and congestive heart failure ( 13,15,16 ).…”

“…PEG-based preparations preserve the histological features of the colonic mucosa ( 14 ), and have been shown to have an acceptable safety profi le in patients with comorbidities, including serum electrolyte imbalances, infl ammatory bowel disease, hepatic dysfunction, renal failure, and congestive heart failure ( 13,15,16 ). PEG is typically administered as a 2-or 4-l solution to achieve an adequate cathartic eff ect.…”

“…Th is is largely due to the number of serious adverse eff ects associated with these preparations. One rare but serious adverse eff ect in particular, acute phosphate nephropathy, has resulted in a black box warning in the label of all sodium phosphate laxatives ( 13 ).…”

A new approach in bowel preparation before colonoscopy in patients with constipation: A prospective, randomized, investigator-blinded trial

“…These agents, which are well tolerated and effective as compared to PEG, unfortunately have the risks of causing dehydration, electrolyte changes and magnesium retention due to osmotic activity (16).…”

Optimal Bowel Cleansing for Colonoscopy in the Elderly Patient

“…Concentrated preparations typically have a reduced volume allowing for improved compliance and readiness to repeat the procedure 23 . The major drawback of the larger volume preparations is the volume required and the taste, however these are safer in regards to causing dehydration or electrolyte abnormalities (for a complete summary of the toxicities of all bowel preparations see Adamcewicz M, et al 24 ). In general, studies comparing different bowel preparations did not report differences in adenoma detection rates, and generally lacked the statistical power to make such a comparison.…”