Yes, ELIXIR is a Scrabble word!

Letter values in Scrabble US: E 1, L 1, I 1, X 8, I 1, R 1.

Is it a valid word?

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

a sweet flavored liquid (usually containing a small amount of alcohol) used in compounding medicines to be taken by mouth in order to mask an unpleasant taste
hypothetical substance that the alchemists believed to be capable of changing base metals into gold
a substance believed to cure all ills

Also: philosopher's stone, philosophers' stone.