Before going to an interview I have always taken a drug test on my own -- you can buy the panel-5 home test at Walgreens. I stay clean for 3 days and I have never had any problem. You can also find the panel-10 test for around $45 (Amphetamines, Barbiturates, Benzos, Cocaine, Marijuana, Methamphetamines, Morphine, Tricyclic-Anti Depressants, Opiates, PCP)

Anyway, here's a link addressing the issue

http://www.cleartest.com/products/index.html