Citric acid / magnesium oxide / sodium picosulfate
"My doctor prescribed Prepopik in preparation for my fourth colonoscopy; prior preps used were ducolax and magnesium citrate per my doctor's instructions which always worked well.  The prepopik did not and, in fact, I went through all of the steps to the "T", i.e., no solid food the day prior, first packet at 4 with five 8 oz. cups of water; second packet at 8 with three 8 oz cups of water. I thought the regimen worked but to my (and the doctor's) amazement, after the start of the colonoscopy too much stool was discovered in my body and the colonoscopy could not be performed. UNBELIEVABLE; and for this I paid $50 and my insurance company paid $52.  Would never recommend it."