Comparison of the Effects of Different Doses of Polyethylene Glycol 4000 (Pidrolax) Versus Castor Oil on Bowel Preparation for Colonoscopy: A Prospective Double Blind Randomized Clinical Trial

Shahram Agah, AmirHosein Faghihi, SeyedMohammad Fereshtehnejad, Amir Shirali, SeyedMorteza Hashemi, Abbas Salami, Siamak Khaleghi, Amad Nazifi


Background: Nowadays colonoscopy has a very important role in screening colorectal cancers. In addition, adequate bowel preparation is critical to colonoscopy, as a poor preparation may obscure pathology or prevent full colonoscopy. As it is estimated that unsuccessful colonoscopy leads to second procedures in up to 20% of patients, we sought to compare the effects of different doses of polyethylene glycol (PEG) versus castor oil based lavage preparation for colonoscopy.

Materials and Methods: In this double blind, randomized clinical trial 117 patients who were supposed to undergo colonoscopy, were allocated randomly into 4 groups in order to receive different lavage preparation protocols: 29 patients under 2 sachets of PEG (group A), 30 patients under 3 sachets of PEG (group B), 32 patients under 4 sachets of PEG (group C) and 26 patients under castor oil (group D). All the used PEG were Macrogol 4000 produced by Sepidaj pharmacy. The quality of bowel preparation was assessed using a scale of 1 to 8 and the higher the grade was, the poorer the bowel was prepared.

Results: The highest and lowest mean grade of colonoscopy preparation were seen in groups A (2.79, SEM=0.36)-the worst preparation-and D (2.46, SEM=0.35)-the best preparation-respectively. However, the difference was not statically significant (p=0.224).The highest and lowest number of patients who were needed to repeat colonoscopy because of poor preparation were also seen in groups A (24.1%) and D (7.7%), respectively.

Conclusion: It seems that usage of PEG may accompany with less gastrointestinal complications such as nausea and vomiting, compared with castor oil; although, no significant difference in quality of bowel preparation was seen in our study.


Colonoscopy; Bowel preparation; Polyethylene glycol Castor oil

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