Definition of drug:
substance used to treat an illness, relieve a symptom or modify a chemical process in the body for a specific purpose; a substance, often addictive, which affects the central nervous system
"1971: We were somewhere around Barstow on the edge of the desert when the drugs began to take hold. -- Hunter S. Thompson, Fear and Loathing in Las Vegas (Harper Perennial 2005, p. 3)"
to administer intoxicating drugs to, generally without the recipient's knowledge or consent; to add intoxicating drugs to with the intention of drugging someone
"she suddenly felt strange, and only then realized she'd been drugged."