17. Positive toxicology screen for any of the following drugs: cocaine, opiates, methadone, benzodiazepines, barbiturates, amphetamines, methamphetamines, or PCP. A. Participants with valid prescriptions for opiates, benzodiazepines, barbiturates, amphetamines or methadone will not be excluded. B. Participants failing the toxicology screen will be allowed to re-screen once. If they test positive again, they will not be allowed to return for 90 days.