Yes, DOPING is a Scrabble word!

Letter values in Scrabble US: D 2, O 1, P 3, I 1, N 1, G 2.

Is it a valid word?

DOPING is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

take drugs to improve one's athletic performance
add impurities to (a semiconductor) in order to produce or modify its properties
give a narcotic to

Also: dope up.