Drug tests are generally used to detect 5 categories: Opiates (opium, morphine, heroin, etc.), Cocaine (crack, coke), Amphetamines, Marijuana, Phencyclidine (PCP, angel dust). On the other hand, pre-employment drug tests may also be used to detect methaqualone, methadone, hydrocodone, barbiturates, propoxyphene, or ethanol.