Are there any risks in taking Colon Cleansing pills?

My brother-in-law was telling my husband and I about his friend that took them and he said they work great. We’re going to get some at GNC today and we want to know more about them. We don’t want to have the whole tube-up-the-butt thing so we hear that the pills work the same. Is that true? Colon cleansing apparently makes you feel tons better so we want to try it.
another question, do they really work? do they really make you feel better? we would only take them like every 6 months, you’re only supposed to cleanse your colon like once a year or something.