7. negative urine drug screen including amphetamine, barbiturates, benzodiazepines, cannabinoid, cocaine, opiates, methadone and phencyclidine with the following exceptions: positive tests for amphetamines, barbiturates, benzodiazepines, or opiates may be allowed provided the subject has a valid prescription and is on a stable regimen that complies with Exclusion Criteria, Section 6.3.2.