Alright now you are talking my line of work... here is what I would recommend as I work with lab techs, who preform these tests for the medical research group that I work for. My first questoin is how much do you weigh and how tall are you? Weight is an important fact and so is your bodies fat content. The substances that labs/tests are searching for in you urine samples are stored in fat cells. They can take anywhere from 2 days to 8 weeks to get rid of depending on your body size, motabelism, ect. What I would recommend doing is really intense cardio work outs, as that is the best way to sweat out and what not. Sweating is actually good for th process, and drink a ton of water i am talking 100oz + a day, you will be pissing every 10 mins or so, but do that up until the day before you go in. Also go to your local head shop they sell all kinds of drinks and what not. Find a cleansing drink, and take a couple of them a few days in advance before you go in and do this as they help to "clean" up your system. Just remember pace your self with the water so you do not kill your self, and stay near pretty close to a toilet. Honestly the intense cardio work outs will help you out the most go to a spin class at a local gym or go on one or more five miles runs a day. Best of luck to you.