How to neutralize THC

First I'd like to say hello to everybody, since I'm new here. Hi!!

And now comes my question:

Does anybody know, how to clean the trail of THC in your system? A friend of mine has came up against some troubles and he has to give a negative THC-test in 3 days. He will have to give his urine.
In order to turn negative he hasn't been smoking now for almost two weeks and he's been drinking a lot of watter. I already told him he should drink some lemon acid (or citron acid - don't really know how's it called in English) before he goes to the test. But nevertheless he's still affraid he's gonna be positive.
So if anyone knows any trick that might help, please don't hesitate to write.

Thank you for your answers!

 

What is the drug test for? (Probation, Government Job, Regular job, etc.)
They make detox things that are a bit pricey, but if you research some they do make some that work fairly well. If they are on probation or a government job, they may test for the detox's in which case that would come back with a fail for having detox in them...
Otherwise, the day of the test they should wake up fairly early and piss as much as possible. THC is in it's greatest concentration in the first piss of the day. Every piss after that there's a little less THC. Also, have them take Vitamin B-12 the days leading up to the test if they do this. Vitamin B-12 makes your piss more yellow, and when you drink a lot of water it makes your piss turn clear, which I guess they can fail you for.

This is in the medical marijuana forum though, does he have a legitimate excuse from a doctor or something?

 

http://www.neonjoint.com/passing_a_drug_test/index.html

Scroll down past all the ads if you want info on how to pass without using the product they endorse.