Oxygen based cleansers like Oxypowder and colosan work by liquifying fecal matter therefore causing "diarrhea". Fiber cleansers work by bulking up the bowels and will not cause diarrhea; P&B shakes are in this category, along with colonix and blessed herbs. Make sure you get plenty of water to avoid constipation; also, there might be a need to stimulate the bowels along with the fiber shakes and colonix and blessed herbs cleansers address that by adding ingredients like senna leaf and cascara sagrada.
Mike