Yes, MEDLARS is a Scrabble word!

Letter values in Scrabble US: M 3, E 1, D 2, L 1, A 1, R 1, S 1.

Is it a valid word?

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

relational database of the United States National Library of Medicine for the storage and retrieval of bibliographical information concerning the biomedical literature
small deciduous tree of southern Africa having edible fruit
small deciduous Eurasian tree cultivated for its fruit that resemble crab apples
a South African globular fruit with brown leathery skin and pithy flesh having a sweet-acid taste
crabapple-like fruit used for preserves

Also: medical literature analysis and retrieval system, wild medlar, wild medlar tree, vangueria infausta, medlar tree, mespilus germanica.