I use Oxy-Power whenever I'm feeling sluggish/bloated/constipated & they can be effective in several hours, depending on how many capsules you take. For example, I may take 5 or 6 when I have been constipated for days & they can start to work in a few hours. They have a purging effect which can of course prove 'inconvenient' if you are not constantly near a toilet. Also, I resorted to taking them in the evenings recently which can result in the urgency to 'go' in the early hours of the morning; hence disturbed sleep. Your stomach will start to rumble/churn but there is no discomfort just the sense that they are taking effect. Unfortunately, they do not cure what might be causing sluggish bowels but they restore a feeling of well-being. I personally haven't noticed a problem when stopping taking them ie a return to normal bowel movements. I always keep a stock of these in my medicine cupboard as I guess I am just prone to constipation.