When did people start using the slang dope?

The earliest use of the Word was from about 1807; it is probably from the Dutch Word "doop", which means "thick liquid or paste". Its association with drugs may have come from the practice of smoking opium that had a pasty, semi-liquid texture. At some point the Word dope came to mean inside information as in "what's the dope on the second race?" in which horses may have been drugged ( or "doped") to alter the race's outcome.