I did exstasy, LSD and speed in major quantities during my party years - a five year period during my midtwenties going out every weekend and doing recreational drugs whilst dancing. I have done four liver flushed and three major Colon Cleanses without having the past drugs woosh that you worry might happen. I worried about this too. I think you will be fine: I had no "drug" like experiences at all whilst cleansing, just physical reactions such as nausea and vomiting and major emotional releases during colon cleansing- mainly weeping constantly. But I think the weping has more to do with releasing old childhood trauma than with toxins from partying.
Good lucvk with your cleanse, it is well worht doing..