A drug is any substance that alters the body’s structure or function. It can serve medical purposes—such as diagnosing, treating, or preventing disease—and may come in the form of chemical compounds or biological products. More broadly, the term also includes psychoactive or intoxicating substances like alcohol, which may be legal or illegal depending on local laws.

This is probably the biggest category on the english part of Drugwiki, most articles are listed here.