There is actually a delay of a few hours after you take it until the reaction gets into full swing, then it lasts for 6 - 10 hours, or until you eliminate the bulk of it from your system. Keep in mind that the half life of chlorite is around 42 hours, so you could continue to have reactions over a few days, but they should be at a reduced intensity.
If you can manage it, now would be the best time to have a colonoscopy... [sarcastic smile icon]