It is an inappropriate assumption to perceive narcotics, as simply lethal substances. There are some instances where taking a drug appropriately may, in fact, benefit someone. This, however, is only intended for short-term use and will eventually make things worse than originally anticipated, when abuse and addiction come into play. Essentially, it can be thought of like an addict in addition to drugs, results in detrimental factors.
The addict initially consumes substances and at first glance, it appears that the drugs result in more positive outcomes than negative. They may take a stimulant and find that they have an easier time developing energy and the ability to be more productive. They may consume a depressant and have an easier time relaxing and falling asleep at night. These positive factors serve as nothing more than false promises and result in more destructive mechanisms in the long run.
Over time the drugs begin to wear off and the person needs to consume large quantities to achieve the original results. The person keeps increasing the doses to the point where they can not even achieve the same effects, no matter how much they use. There may exist an unlimited supply of drugs but there is no such thing as an unlimited supply of neurotransmitters in the brain released by the drugs.
Over time, the brain runs low on the chemicals that the drugs release to give the user a sense of euphoria. This leaves the addict feeling miserable due to chemical imbalances. In addition to this, the user begins losing their ambitions, leading them to engage in behaviors they later regret and feel shame towards. The disease of addiction is devious and will lead the addict to eventually lose sight of who they are and everything they cherish.