Principles of Health: Prescription Drug Abuse is an important and timely volume that addresses a serious public health issue in the United States. Prescription drug abuse takes many forms, from taking a friend's painkillers for your backache to misusing pills to lose weight or get high. Although most people take prescription medications responsibly, an estimated 20 million have misused prescription medications in the past year. The three classes of medications most commonly misused are opioids (usually prescribed to treat pain); central nervous system depressants (used to treat anxiety and sleeplessness); and stimulants (most often prescribed to treat attention deficit hyperactivity disorder and narcolepsy).