Yes, SULPHAS is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, L 1, P 3, H 4, A 1, S 1.

Is it a valid word?

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

antibacterial consisting of any of several synthetic organic compounds capable of inhibiting the growth of bacteria that require PABA

Also: sulfa drug.