You do not have to add so much at first. It is common to work up to the full amount of cayenne. My first cleanse, I began with a sprinkle and now I am heaping it in. Your body begins to crave it since it is so healing for the intenstines and colon.
Also, if the problem continues, I would try another brand of cayenne. I really love the organic frontier brand I found. I bought in bulk and for a 30 day fast it ran around 2-3 bucks for a bag.