Darija,
The Mayo Clinic is a good reference site when you want fair assessments of complementary and alternative medicine in the world of Western medicine. Their
colonics page outlines concerns and precautions for those who are considering colon cleansing but have other health problems.
The most important advice is to talk to your doctor ahead of time to ask about specific interactions or interference.
A reminder to all patients looking to combine approaches to health: Even if you don't follow your doctor's advice, let the doctor know of any other treatments or self-treatments you try and any supplements, herbal remedies, or other non-prescription medication you take. The key to taking care of yourself is
do ask, do tell!