A drug that legally requires a medical prescription to be dispensed. Over-the-counter drugs drug that legally requires a medical prescription to be dispensed. In contrast, over-the-counter drugs can be obtained without a prescription. prescription drugs that effect the brain, including opioid pain relievers, stimulants, and depressants, can cause physical dependence that could lead to addiction. Medications that affect the brain can change the way it works—especially when they are taken over an extended period of time or with escalating doses. They can change the reward system, making it harder for a person to feel good without the drug and possibly leading to intense cravings, which make it hard to stop using.