Short answers, pulled from the story.
The word drug emerged from the Middle Dutch word droge meaning dry in the 14th century to refer to medicinal plants preserved as dry matter inside wooden barrels. Spanish lexicographer Federico Corriente Córdoba proposed an even older lineage tracing the term to an early Romanized form of the Al-Andalus language possibly transcribed as hatruka.
A single drug may help only 4 to 25 percent of the people who take it revealing a startling inefficiency in modern pharmacology. The activity of a drug often depends entirely on the genotype of the patient meaning that a treatment effective for one individual might be useless or even dangerous for another.
Native Americans have used peyote as a major source of the psychedelic mescaline for at least five thousand years while Amazonian shamans utilize ayahuasca to achieve religious ecstasy. The Mazatec people maintain a long and continuous tradition of using Salvia divinorum to facilitate visionary states of consciousness during spiritual healing sessions.
At high doses this medication can become highly addictive leading to serious consequences including psychosis anxiety and heart problems. Intravenous use of methylphenidate can lead to emphysematous damage to the lungs a condition known as Ritalin lung.
The Single Convention on Narcotic Drugs was brought about in 1961 to prohibit the use of narcotics save for those used in medical research and treatment. A second treaty the Convention on Psychotropic Substances had to be introduced in 1971 to deal with newer recreational psychoactive and psychedelic drugs.
The Anatomical Therapeutic Chemical Classification System assigns drugs a unique alphanumeric code that assigns it to specific drug classes within the ATC system. Another major classification system is the Biopharmaceutics Classification System which groups drugs according to their solubility and permeability or absorption properties.