I have used both conventional and natural methods. I hated the preparation I had to drink for the colonoscopy.
I read some information that said that Colonix is a scam. After I read that the main ingredient in Colonix is psyllium, I knew that I wasn't about to use Colonix. I do not advise people to use psyllium, because it is irritating to the gut. It not only bothers my own GERD, but I find that initially it makes me more constipated than I was to begin with. This website also mentioned that aside from preparing your colon for tests or surgery, you should not be forcing your colon to empty itself too quickly because it sloughs off the natural bacteria, the friendly bacteria, that you NEED in your gut. I suggest using flaxseed meal instead. It is easier on the gut, and it has a pleasant taste and can be simply sprinkled in and on your usual foods you eat. You still need to drink plenty of water, which you should do anyway.
Cascara Sagrada is very potent and it will cause you to have diarhea IF you take too much of it. I've been using just ONE at bed time, which seems to be just enough to help pull some water into the colon, and I've been able to use less of the anti-spasmodic, Bentyl, since the cramping I get is directly related to being constipated, in spite of eating a very healthy diet and drinking lots of water. The directions that were on the old bottle of this stuff said to take 900 mg twice a day, which is TOO MUCH and will lead to diarhea. The new bottle says to do what I instinctively figured out, to simply take 450 mg one time at bed time. It isn't a good idea to take more than the ONE at night time before going to bed. Do NOT over use this potent herb! Use care and discretion.
If you're simply preparing your colon for tests or surgery, then you can follow the directions from the old bottle as described above. You may need more time than the 48 hours required with the conventional medication for this. So, you would have to be on the liquid diet for perhaps another day or so. This is one of those times that I would actually suggest using the conventional method when you're preparing for tests or surgery.