I've done the miralax and the mag. citrate. They should give you a prep sheet and instructions- I'm ocd about that stuff and follow it to the letter :) The magn. citrate didn't make me cramp at all, but I never really felt "cleaned out." It was for me, much milder than the miralax, but the morning of I was afraid I wasn't emptied out... The miralax cleaned me right out, and I spent much more time in the bathroom- a lot more urgently... the only thing that was really hard at the end was drinking all that gatorade. I had to drink a LOT and I think the sugars from the gatorade made me feel pretty sick and shaky. It was a lot of sugar calories in a short time. Next time I might dilute some of it with water. I know you need the electrolytes, but it was too much for me.
At approximately 5:00 p.m. the night prior to your procedure, mix the MiraLax (entire bottle 238 g) or (Glycolax, the generic brand) into 32 ounces of Gatorade or any other clear non-carbonated liquid. Please shake well. Drink an 8 ounce glass of the mix every hour on the hour until finished.
Be sure to drink at least 3 cups of clear liquids after the prep, but prior to midnight. You may not eat or drink anything after midnight.