Scientifically nicotine is described as an alkaloid found in the nightshade family of plants (Solanaceae) which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves. Due to its properties it was used in the past as antiherbivore chemical and insecticide. Even today nicotine analogs [...]

Abuse of benzodiazepines is particularly high among heroin and cocaine abusers. A large percentage of people entering treatment for narcotic or cocaine addiction also report abusing benzodiazepines.

Methamphetamine is the second drug used most frequently after alcohol and marijuana combined, a highly addictive drug with potent central nervous system stimulant properties. The methamphetamine pharmaceutical products were available  in ’60s. It was forbidden in 1971.
However, illegal, in the ’80s methamphetamine took back it’s place and it is currently considered a major drug of [...]

It covers the chemical process of drugs and alcohol addiction.