I think what they mean is the pill physically takes up to 25 hours to leave your system but the effects of it last longer.
I understand what you mean though. I still have effects from pills that I haven't been on in weeks/months/years.
current: 45 mg prednisone, 50 mg Imuran, 54 mg iron, 10,000 iu vit D, VSL, culturelle, benebiotics, l-glutamine, collagen
diet: scd/paleo aug 2012- lots of meat and fermented foods (kefir, sauerkraut), little fiber, avocados, oils.
goal: be healthy no matter what it takes.