7.1 Drug screens that work:
7.1.1 Aspirin: According to Jeff Nightbyrd, there is testing industry data that taking 4 aspirins a few hours prior to the test might help you. ". . . aspirin interferes with the Syvia [sic] EMIT assay. It seems that aspirin absorbs at the same wavelength that NAD does which is how it interferes with the assay" (Clin Chem 34 (90) 602-606). Two reliable sources have tested aspirin and found it to interfere with the EMIT. In the future they will try to find a way to circumvent this test flaw. Until then, I certainly recommend taking advantage of the situation and using aspirin.
7.2 Drug screens that do not work:
7.2.1 Goldenseal: Goldenseal has shown to work on occasion. However, some labs are reportedly testing for Goldenseal. Goldenseal is very unreliable, and California NORML advises against using it. Goldenseal (as a screen) only works on the TLC test, which is not used anymore.
7.2.2 Niacin: Niacin has been shown to work on occasion. Byrd Labs tests conclude that niacin doesn't work at all. In other words, something else probably caused a negative, not the niacin.
7.2.3 Zinc sulfate: Zinc sulfate is claimed to bond with THC metabolites, and because it's a solid, it gets passed as stool rather than urine. Jeff Nightbyrd says it does nothing. Anne Watters Pearson said "zinc sulfate is no miracle drug for pissing. Forget it."
7.3 Untested drug screens:
7.3.1 Puri-Blend (c): Puri-Blend is claimed to "block" metabolites from entering the bloodstream and to "neutralize" all drugs in the urine. I don't believe it myself. Sold in GNC stores.
7.3.2 The Stuff (c): The Stuff is claimed to absorb toxins in the body and block detection of true and false positives. Sold by J&J Enterprises.