When used as prescribed by a doctor, prescription medicines can be helpful in treating many illnesses. Stimulants are helpful in managing attention-deficit/hyperactivity disorder (ADHD) and narcolepsy. Central nervous system (CNS) depressants treat anxiety, panic, and sleep disorders. Opioids are prescribed to treat pain, coughing, and diarrhea. But when these medicines are misused, they can have serious consequences. Read the DrugFacts on Prescription CNS Depressants, Prescription Opioids, and Prescription Stimulants.