Abused drugs distorts the functions of neurotransmitters by mimicking or blocking neurotransmitters in uncontrolled ways. This distorts our behaviors that are regulated by the brain and alters our sensations. Uncontrolled means that the brain itself doesn’t have any mechanism to regulate them. Because abused drugs in the brain are chemical signals, they are similar to neurotransmitters. But they are different from neurotransmitters in important ways. Neurotransmitters and the brain have coevolved over eons of time, and they coexist quite peacefully. Neurotransmitters are beautifully regulated by the brain. When their levels are low, they are synthesized. When made, they are safely stored in vesicles. When needed, they are released from specific neurons. After they are released and stimulate receptors, their action is terminated by breakdown, diffusion, or reuptake. Drugs of abuse, on the other hand, get into the brain and affect neurotransmission, but the brain does not have ways to handle or terminate their actions! Drug levels in the brain are under the control of the drug taker and not regulated by synthetic enzymes or release or reuptake in the brain.