A 12-panel drug test is a screening method designed to detect the presence of twelve different substances in a person's system. These substances typically include commonly abused drugs such as marijuana, cocaine, opiates, amphetamines, benzodiazepines, barbiturates, methadone, propoxyphene, phencyclidine (PCP), ecstasy, oxycodone, and methamphetamine. The comprehensive nature of the 12-panel test makes it an effective tool for identifying a variety of illicit substances.