About a third of some 4,000 patients who gave urine samples turned up negative for their prescribed stimulants, Mancia Ko, PharmD, of Ingenuity Health -- a service of Ameritox, a medication monitoring company -- and colleagues reported at the American Professional Society of ADHD and Related Disorders (APSARD) meeting here. In samples where the prescribed stimulant wasn't detected, THC was present more than 20% of the time, and some combination of a nonprescribed opioid, nonprescribed benzodiazepine, THC and/or cocaine was found more than 38% of the time, they reported.